LITHIUM-FREE ION EXCHANGEABLE GLASSES

Abstract

A glass composition includes: from 50 mol % to 70 mol % SiO.sub.2; from 15 mol % to 30 mol % Al.sub.2O.sub.3; from 5 mol % to 20 mol % Na.sub.2O; from 0 mol % to 15 mol % MgO; and from 0 mol % to 15 mol % CaO. The glass composition is free or substantially free of Li (i.e., Li.sub.2O). The sum of MgO and CaO in the glass composition may be from 0 mol % to 30 mol %.

Claims

1. A glass composition comprising: greater than or equal to 50 mol % and less than or equal to 70 mol % SiO.sub.2; greater than or equal to 15 mol % and less than or equal to 30 mol % Al.sub.2O.sub.3; greater than or equal to 5 mol % and less than or equal to 20 mol % Na.sub.2O; greater than or equal to 0 mol % and less than or equal to 15 mol % MgO; and greater than or equal to 0 mol % and less than or equal to 15 mol % CaO, wherein the glass composition is free or substantially free of Li; and RO is greater than 0 mol % and less than or equal to 30 mol %, wherein RO is the sum of MgO and CaO.

2. The glass composition of claim 1, wherein the glass composition comprises greater than or equal to 16 mol % and less than or equal to 28 mol % Al.sub.2O.sub.3.

3. The glass composition of claim 1, wherein the glass composition comprises greater than or equal to 7 mol % and less than or equal to 18 mol % Na.sub.2O.

4. The glass composition of claim 1, wherein the glass composition comprises greater than 0 mol % and less than or equal to 13 mol % MgO.

5. The glass composition of claim 1, wherein the glass composition comprises greater than 0 mol % and less than or equal to 13 mol % CaO.

6. The glass composition of claim 1, wherein RO is greater than or equal to 1 mol % and less than or equal to 25 mol %.

7. The glass composition of claim 1, wherein (Na.sub.2O+RO)/Al.sub.2O.sub.3 is greater than or equal to 0.5 and less than or equal to 1.5.

8. The glass composition of claim 1, wherein the glass composition comprises greater than 0 mol % and less than or equal to 5 mol % P.sub.2O.sub.5.

9. The glass composition of claim 1, wherein the glass composition comprises greater than 0 mol % and less than or equal to 10 mol % Y.sub.2O.sub.3.

10. The glass composition of claim 1, wherein the glass composition comprises greater than 0 mol % and less than or equal to 5 mol % ZrO.sub.2.

11. The glass composition of claim 1, wherein the glass composition comprises greater than 0 mol % and less than or equal to 1 mol % SnO.sub.2.

12. The glass composition of claim 1, wherein the glass composition has a Young's Modulus greater than or equal to 60 GPa.

13. The glass composition of claim 1, wherein the glass composition has a fracture toughness greater than or equal to 0.75 MPa.Math.m.sup.1/2.

14. The glass composition of claim 1, wherein the strain point is greater than or equal to 600? C.

15. A method of forming a glass article, the method comprising: heating a glass composition, the glass composition comprising: greater than or equal to 50 mol % and less than or equal to 70 mol % SiO.sub.2; greater than or equal to 15 mol % and less than or equal to 30 mol % Al.sub.2O.sub.3; greater than or equal to 5 mol % and less than or equal to 20 mol % Na.sub.2O; greater than or equal to 0 mol % and less than or equal to 15 mol % MgO; and greater than or equal to 0 mol % and less than or equal to 15 mol % CaO, wherein the glass composition is free or substantially free of Li; and RO is greater than 0 mol % and less than or equal to 30 mol %, wherein RO is the sum of MgO and CaO; and cooling the glass composition to form the glass article.

16. The method of claim 15, further comprising strengthening the glass article in a first ion exchange bath at a temperature greater than or equal 500? C. for a time period greater than or equal to 1 hour and less than or equal to 32 hours to form an ion exchanged glass article.

17. The method of claim 16, further comprising strengthening the glass article in a second ion exchange bath at a temperature greater than or equal to 300? C. for a time period greater than or equal to 1 hour and less than or equal to 32 hours to form an ion exchanged glass article.

18. The method of claim 16, wherein the ion exchanged glass article comprises a surface compressive stress greater than or equal to 350 Mpa and less than or equal to 900 MPa, and a depth of compression greater than or equal to 80 ?m.

19. The method of claim 15, wherein the first ion exchange bath, the second ion exchange bath, or both comprises KNO.sub.3.

20. The method of claim 15, wherein the first ion exchange bath, the second ion exchange bath, or both comprises NaNO.sub.3.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0098] FIG. 1A is a representation of a non-frangible sample after a frangibility test;

[0099] FIG. 1B is another representation of a non-frangible sample after a frangibility test;

[0100] FIG. 2A is a representation of a borderline frangible sample after a frangibility test;

[0101] FIG. 2B is another representation of a borderline frangible sample after a frangibility test;

[0102] FIG. 3A is a representation of a frangible sample after a frangibility test;

[0103] FIG. 3B another representation of a frangible sample after a frangibility test;

[0104] FIG. 4 is a plan view of an electronic device incorporating any of the glass articles according to one or more embodiments described herein;

[0105] FIG. 5 is a perspective view of the electronic device of FIG. 4;

[0106] FIG. 6 is a plot of stress (y-axis: stress; in MPa) as a function of a depth of an ion exchanged glass article (x-axis: depth; in mm) made from a glass composition according to one or more embodiments described herein;

[0107] FIG. 7 is a plot of stress (y-axis: stress; in MPa) as a function of a depth of ion exchanged glass articles (x-axis: depth; in mm) made from comparative compositions and a glass composition, according to one or more embodiments described herein;

[0108] FIG. 8 is a plot of stress (y-axis: stress; in MPa) as a function of a depth of ion exchanged glass articles (x-axis: depth; in mm) made from glass compositions, according to one or more embodiments described herein;

[0109] FIG. 9A is a photograph of a glass made from a glass composition and subjected to a frangibility test, according to one or more embodiments described herein;

[0110] FIG. 9B is a photograph of a glass made from a glass composition and subjected to a frangibility test, according to one or more embodiments described herein;

[0111] FIG. 10 is a plot of stress (y-axis: stress; in MPa) as a function of a depth of an ion exchanged glass article (x-axis: depth; in mm) made from a glass composition, according to one or more embodiments described herein;

[0112] FIG. 11 is a photograph of a glass made from a glass composition and subjected to a frangibility test, according to one or more embodiments described herein;

[0113] FIG. 12 is a plot of stress (y-axis: stress; in MPa) as a function of a depth of an ion exchanged glass article (x-axis: depth; in mm) made from a glass composition, according to one or more embodiments described herein;

[0114] FIG. 13A is a photograph of a glass made from a glass composition and subjected to a frangibility test, according to one or more embodiments described herein;

[0115] FIG. 13B is a photograph of a glass made from a glass composition and subjected to a frangibility test, according to one or more embodiments described herein;

[0116] FIG. 14 is a plot of stress (y-axis: stress; in MPa) as a function of a depth of ion exchanged glass articles (x-axis: depth; in mm) made from glass compositions according to one or more embodiments described herein;

[0117] FIG. 15A is a photograph of a glass made from a glass composition and subjected to a frangibility test, according to one or more embodiments described herein;

[0118] FIG. 15B is a photograph of a glass made from a glass composition and subjected to a frangibility test, according to one or more embodiments described herein;

[0119] FIG. 16 is a plot of stress (y-axis: stress; in MPa) as a function of a depth of an ion exchanged glass article (x-axis: depth; in mm) made from a glass composition according to one or more embodiments described herein;

[0120] FIG. 17 is a plot of stress (y-axis: stress; in MPa) as a function of a depth of an ion exchanged glass article (x-axis: depth; in mm) made from a glass composition according to one or more embodiments described herein;

[0121] FIG. 18 is a photograph of a glass made from a glass composition and subjected to a frangibility test, according to one or more embodiments described herein; and

[0122] FIG. 19 is a plot of stress (y-axis: stress; in MPa) as a function of a depth of ion exchanged glass articles (x-axis: depth; in mm) made from glass compositions according to one or more embodiments described herein.

DETAILED DESCRIPTION

[0123] Reference will now be made in detail to various embodiments of ion exchangeable glass compositions having improved mechanical durability. According to embodiments, a glass composition may comprise greater than or equal to 50 mol % and less than or equal to 70 mol % SiO.sub.2; greater than or equal to 15 mol % and less than or equal to 30 mol % Al.sub.2O.sub.3; greater than or equal to 5 mol % and less than or equal to 20 mol % Na.sub.2O; greater than or equal to 0 mol % and less than or equal to 15 mol % MgO; and greater than or equal to 0 mol % and less than or equal to 15 mol % CaO. The glass composition is free or substantially free of Li. RO (i.e., MgO+CaO) is greater than 0 mol % and less than or equal to 30 mol %. Various embodiments of ion exchangeable glass compositions and glass articles formed therefrom will be described herein with specific reference to the appended drawings.

[0124] Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent about, it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0125] Directional terms as used hereinfor example up, down, right, left, front, back, top, bottomare made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0126] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order, nor that with any apparatus specific orientations be required. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or that any apparatus claim does not actually recite an order or orientation to individual components, or it is not otherwise specifically stated in the claims or description that the steps are to be limited to a specific order, or that a specific order or orientation to components of an apparatus is not recited, it is in no way intended that an order or orientation be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps, operational flow, order of components, or orientation of components; plain meaning derived from grammatical organization or punctuation, and; the number or type of embodiments described in the specification.

[0127] As used herein, the singular forms a, an and the include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a component includes aspects having two or more such components, unless the context clearly indicates otherwise.

[0128] In the embodiments of the glass compositions and resultant glass articles described herein, the concentrations of constituent components (i.e., SiO.sub.2, Al.sub.2O.sub.3, and the like) are specified in mole percent (mol %) on an oxide basis, unless otherwise specified.

[0129] The term substantially free, when used to describe the concentration and/or absence of a particular constituent component in a glass composition and the resultant glass article, means that the constituent component is not intentionally added to the glass composition and the resultant glass article. However, the glass composition and the resultant glass article may contain traces of the constituent component as a contaminant or tramp in amounts of less than 0.05 weight percent (wt %). As noted herein, the remainder of the application specifies the concentrations of constituent component in mol %. The contaminant or tramp amounts of the constituent components are listed in wt % for manufacturing purposes and one skilled in the art would understand the contaminant and tramp amounts being listed in wt %.

[0130] The terms 0 mol % and free, when used to describe the concentration and/or absence of a particular constituent component in a glass composition and the resultant glass article, means that the constituent component is not present in glass composition and the resultant glass article.

[0131] Fracture toughness (K.sub.IC) represents the ability of a glass composition to resist fracture. Fracture toughness is measured on a non-strengthened glass article, such as measuring the K.sub.IC value prior to ion exchange treatment of the glass article, thereby representing a feature of a glass article prior to ion exchange. The fracture toughness test methods described herein are not suitable for glasses that have been exposed to ion exchange treatment. But, fracture toughness measurements performed as described herein on the same glass article prior to ion exchange treatment correlate to fracture toughness after ion exchange treatment, and are accordingly used as such. The chevron notched short bar (CNSB) method utilized to measure the K.sub.IC value is disclosed in Reddy, K. P. R. et al, Fracture Toughness Measurement of Glass and Ceramic Materials Using Chevron-Notched Specimens, J. Am. Ceram. Soc., 71 [6], C-310-C-313 (1988) except that Y*m is calculated using equation 5 of Bubsey, R. T. et al., Closed-Form Expressions for Crack-Mouth Displacement and Stress Intensity Factors for Chevron-Notched Short Bar and Short Rod Specimens Based on Experimental Compliance Measurements, NASA Technical Memorandum 83796, pp. 1-30 (October 1992). Unless otherwise specified, all fracture toughness values were measured by chevron notched short bar (CNSB) method.

[0132] Density, as described herein, is measured by the buoyancy method of ASTM C693-93.

[0133] The term coefficient of thermal expansion and CTE, as described herein, is measured in accordance with ASTM E228-85 over the temperature range of 0? C. to 300? C. and is expressed in terms of ?10.sup.?7/? C.

[0134] The term strain point, as used herein, refers to the temperature at which the viscosity of the glass composition is 1?10.sup.14.68 poise as measured in accordance with ASTM C598.

[0135] The term melting point, as used herein, refers to the temperature at which the viscosity of the glass composition is 200 poise as measured as described below with respect to the Vogel-Fulcher-Tamman relation.

[0136] The term softening point, as used herein, refers to the temperature at which the viscosity of the glass composition is 1?10.sup.7.6 poise. The softening point is measured according to the parallel plate viscosity method which measures the viscosity of inorganic glass from 10.sup.7 to 10.sup.9 poise as a function of temperature, similar to ASTM C1351M.

[0137] The term annealing point or effective annealing temperature as used herein, refers to the temperature at which the viscosity of the glass composition is 1?10.sup.13.18 poise as measured in accordance with ASTM C598.

[0138] The elastic modulus (also referred to as Young's modulus) of the glass composition, as described herein, is provided in units of gigapascals (GPa) and is measured in accordance with ASTM C623.

[0139] The shear modulus of the glass composition, as described herein, is provided in units of gigapascals (GPa). The shear modulus of the glass composition is measured in accordance with ASTM C623.

[0140] Poisson's ratio, as described herein, is measured in accordance with ASTM C623.

[0141] Refractive index, as described herein, is measured in accordance with ASTM E1967.

[0142] Surface compressive stress is measured with a surface stress meter (FSM) such as commercially available instruments such as the FSM-6000, manufactured by Orihara Industrial Co., Ltd. (Japan). Surface stress measurements rely upon the measurement of the stress optical coefficient (SOC), which is related to the birefringence of the glass article. SOC, in turn, is measured according to Procedure C (Glass Disc Method) described in ASTM standard C770-16, entitled Standard Test Method for Measurement of Glass Stress-Optical Coefficient, the contents of which are incorporated herein by reference in their entirety. The central tension (CT) values are measured using a SCALP technique known in the art. The values reported for central tension (CT) herein refer to the central tension at half the thickness of the glass, unless otherwise indicated.

[0143] In the figures, compression or compressive stress (CS) is expressed as a positive (i.e., >0) stress, and tension or tensile stress or central tension (CT) is expressed as a negative (i.e., <0) stress. Throughout this description, however, when particular values are given, CS and CT may be expressed as positive or absolute values (i.e., as recited herein, CS=|CS|, and CT=|CT|).

[0144] As used herein, depth of compression (DOC) refers to the depth at which the stress within the glass article changes from compressive to tensile. At the DOC, the stress crosses from a compressive stress to a tensile stress and thus exhibits a stress value of zero. DOC values given herein are measured using the refracted near-field (RNF) method, unless otherwise indicated. Depth of compression may be measured using a Scattered Light Polariscope (SCALP), such as a SCALP-05 portable scattered light polariscope.

[0145] When the RNF method is utilized to measure the stress profile, the CT value provided by SCALP is utilized in the RNF method. In particular, the stress profile measured by RNF is force balanced and calibrated to the CT value provided by a SCALP measurement. The RNF method is described in U.S. Pat. No. 8,854,623, entitled Systems and methods for measuring a profile characteristic of a glass sample, which is incorporated herein by reference in its entirety. In particular, the RNF method includes placing the glass article adjacent to a reference block, generating a polarization-switched light beam that is switched between orthogonal polarizations at a rate of between 1 Hz and 50 Hz, measuring an amount of power in the polarization-switched light beam and generating a polarization-switched reference signal, wherein the measured amounts of power in each of the orthogonal polarizations are within 50% of each other. The method further includes transmitting the polarization-switched light beam through the glass sample and reference block for different depths into the glass sample, then relaying the transmitted polarization-switched light beam to a signal photodetector using a relay optical system, with the signal photodetector generating a polarization-switched detector signal. The method also includes dividing the detector signal by the reference signal to form a normalized detector signal and determining the profile characteristic of the glass sample from the normalized detector signal.

[0146] As used herein, depth of layer (DOL) refers to the depth within a glass article at which an ion of metal oxide diffuses into the glass article where the concentration of the ion reaches a minimum value. DOL values given herein are measured using a surface stress meter (FSM) such as commercially available instruments such as the FSM-6000.

[0147] As used herein, the term knee region refers to a part of a stress profile of an ion exchanged glass article that starts at the first slope change in the compressive stress region and ends at the depth where the stress changes from compressive stress to tensile stress.

[0148] As used herein, the term knee refers to the depth of an ion exchanged glass at which the knee region begins.

[0149] As used herein, the term knee stress refers to the stress at which the knee region begins.

[0150] The term Vogel-Fulcher-Tamman (VFT) relation, as used herein, describes the temperature dependence of the viscosity and is represented by the following equation:

[00001]$\log ?=A+\frac{B}{T-T_o}$

where ? is viscosity. To determine VFT A, VFT B, and VFT T.sub.o, the viscosity of the glass composition is measured over a given temperature range. The raw data of viscosity versus temperature is then fit with the VFT equation by least-squares fitting to obtain A, B, and T.sub.o. With these values, a viscosity point (i.e., 200 P Temperature (melting point), 35,000 P Temperature, and 200,000 P Temperature) at any temperature above softening point may be calculated.

[0151] The term liquidus viscosity, as used herein, refers to the viscosity of the glass composition at the onset of devitrification (i.e., at the liquidus temperature as determined with the gradient furnace method according to ASTM C829-81).

[0152] The term liquidus temperature, as used herein, refers to the temperature at which the glass composition begins to devitrify as determined with the gradient furnace method according to ASTM C829-81.

[0153] As used herein, the frangibility limit refers to the central tension or stored strain energy above which the glass article exhibits frangible behavior. Frangibility or frangible behavior refers to specific fracture behavior when a material is subjected to an impact or insult. As utilized herein, a glass article is considered non-frangible when it exhibits no branching in a test area as a result of a frangibility test. As utilized herein, a branch originates at the impact point, and a fragment is considered to be within the test area is any part of the fragment extends into the test area. The fragments, bifurcations, and branches are counted based on any 25 mm by 25 mm square centered on the impact point. Thus, a glass article is considered non-frangible if it does not show any branching for any 25 mm by 25 mm square centered on the impact point where the breakage is created according to the procedure described below. A glass article is considered borderline frangible or close to the frangibility limit if a glass article shows less than or equal to 5 braches for any 25 mm by 25 mm square centered on the impact point. A glass article is considered frangible if a glass article shows more than 5 branches for any 25 mm by 25 mm square centered on the impact point. In a frangibility test, an impact probe is brought in to contact with the multi-phase glass, with the depth to which the impact probe extends into the multi-phase glass increasing in successive contact iterations. The step-wise increase in depth of the impact probe allows the flaw produced by the impact probe to reach the tension region while preventing the application of excessive external force that would prevent the accurate determination of the frangible behavior of the glass article. In embodiments, the depth of the impact probe in the multi-phase glass may increase by about 5 ?m in each iteration, with the impact probe being removed from contact with the glass article between each iteration. The test area is any 25 mm by 25 mm square centered at the impact point. While coatings, adhesive layers, and the like may be used in conjunction with the multi-phase glass described herein, such external restraints are not used in determining the frangibility or frangible behavior of the multi-phase glass. In embodiments, a film that does not affect the fracture behavior of the multi-phase glass may be applied to the multi-phase glass prior to the frangibility test to prevent the ejection of fragments from the multi-phase glass.

[0154] FIG. 1A depicts a non-frangible test result. As shown in FIG. 1A, the test area is a square that is centered at the impact point 130, where the length of a side of the square a is 25 mm. The sample shown in FIG. 1A includes two fragments 142 and no branches. Since the sample shown in FIG. 1A does not have any branches, it is considered non-frangible.

[0155] FIG. 1B depicts another non-frangible test result. As shown in FIG. 1B, the non-frangible sample is centered at the impact point 130 and includes six fragments 142 and no branches. Since the sample shown in FIG. 1B contains no branches, it is considered non-frangible.

[0156] A borderline frangible sample is depicted in FIG. 2A. The sample shown in FIG. 2A is centered at the impact point 130 and includes nine fragments 142 and three branches 140. Since the sample shown in FIG. 2A contains five or less branches, it is considered borderline frangible.

[0157] Another borderline frangible sample is depicted in FIG. 2B. As shown in FIG. 2B, the sample is centered at the impact point 130 and includes seven fragments 142 and one branch 140. Since the sample shown in FIG. 2B contains five or less branches, is considered borderline frangible.

[0158] A frangible sample is depicted in FIG. 3A. The sample is centered at the impact point 130 and includes seventeen fragments 142 having twelve branches 140. Since the sample shown in FIG. 3A contains more than 5 branches, it is considered frangible.

[0159] Another frangible sample is depicted in FIG. 3B. The sample is centered at the impact point 130 and includes nineteen fragments 142 having twelve crack branches 140. Since the sample depicted in FIG. 3B contains more than 5 branches, the sample is considered frangible.

[0160] In the frangibility test described herein, the impact is delivered to the surface of the glass article with a force that is just sufficient to release the internally stored energy present within the strengthened glass article. That is, the point impact force is sufficient to create at least one new crack at the surface of the strengthened glass sheet and extend the crack through the compressive stress layer into the region that is under central tension (CT).

[0161] Chemical strengthening processes have been used to achieve high strength and high toughness in alkali silicate glasses. For example, Li.sub.2O, which has a relatively high field strength as compared to other alkali oxides such as Na.sub.2O, may be included in the glass compositions to impart relatively higher Young's modulus and fracture toughness and enable ion exchangeability. However, lithium prices are increasing due to the rapid adoption of electric vehicles.

[0162] Disclosed herein are glass compositions and glass articles formed therefrom which mitigate the aforementioned problems. Specifically, the glass compositions and the resultant glass articles disclosed herein are lithium-free or substantially lithium-free and comprise Na.sub.2O, Al.sub.2O.sub.3 and alkaline earth oxides (i.e., MgO and CaO), which results in ion exchangeable glass compositions having improved Young's modulus and fracture toughness.

[0163] The glass compositions and resultant glass articles described herein may be described as aluminosilicate glass compositions and articles and comprise SiO.sub.2 and Al.sub.2O.sub.3. The glass compositions and resultant glass articles described herein also include alkaline earth oxides (i.e., MgO and/or CaO) to increase Young's modulus and/or fracture toughness. The glass compositions and resultant glass articles described herein are free or substantially free of Li and instead include Na.sub.2O to enable the ion exchangeability of the glass compositions.

[0164] SiO.sub.2 is the primary glass former in the glass compositions described herein and may function to stabilize the network structure of the glass articles. The concentration of SiO.sub.2 in the glass compositions and resultant glass articles should be sufficiently high (i.e., greater than or equal to 50 mol %) to provide basic glass forming capability. The amount of SiO.sub.2 may be limited (i.e., less than or equal to 70 mol %) to control the liquidus temperature of the glass composition, as the liquidus temperature of pure SiO.sub.2 or high SiO.sub.2 glasses is undesirably high. Thus, limiting the concentration of SiO.sub.2 may aid in improving the meltability and the formability of the resulting glass article.

[0165] Accordingly, in embodiments, the glass composition and resultant glass article may comprise greater than or equal to 50 mol % and less than or equal to 70 mol % SiO.sub.2. In embodiments, the concentration of SiO.sub.2 in the glass composition and the resultant glass article may be greater than or equal to 50 mol %, greater than or equal to 52 mol %, or even greater than or equal to 54 mol %. In embodiments, the concentration of SiO.sub.2 in the glass composition and the resultant glass article may be less than or equal to 70 mol %, less than or equal to 67 mol %, less than or equal to 65 mol %, or even less than or equal to 63 mol %. In embodiments, the concentration of SiO.sub.2 in the glass composition and the resultant glass article may be greater than or equal to 50 mol % and less than or equal to 70 mol %, greater than or equal to 50 mol % and less than or equal to 67 mol %, greater than or equal to 50 mol % and less than or equal to 65 mol %, greater than or equal to 50 mol % and less than or equal to 63 mol %, greater than or equal to 52 mol % and less than or equal to 70 mol %, greater than or equal to 52 mol % and less than or equal to 67 mol %, greater than or equal to 52 mol % and less than or equal to 65 mol %, greater than or equal to 52 mol % and less than or equal to 63 mol %, greater than or equal to 54 mol % and less than or equal to 70 mol %, greater than or equal to 54 mol % and less than or equal to 67 mol %, greater than or equal to 54 mol % and less than or equal to 65 mol %, or even greater than or equal to 54 mol % and less than or equal to 63 mol %, or any and all sub-ranges formed from any of these endpoints.

[0166] Like SiO.sub.2, Al.sub.2O.sub.3 may also stabilize the glass network and additionally provides improved mechanical properties and chemical durability to the resulting glass article. The amount of Al.sub.2O.sub.3 may also be tailored to the control the viscosity of the glass composition. The concentration of Al.sub.2O.sub.3 should be sufficiently high (i.e., greater than or equal to 15 mol %) such that the glass composition and the resultant glass article have the desired Young's Modulus (i.e., greater than or equal to 60 GPa) and the desired fracture toughness (greater than or equal to 0.75 MPa.Math.m.sup.1/2). However, if the amount of Al.sub.2O.sub.3 is too high (i.e., greater than 30 mol %), the viscosity of the melt may increase, thereby diminishing the formability of the glass composition. In embodiments, the glass composition and resultant glass article may comprise greater than or equal to 15 mol % and less than or equal to 30 mol % Al.sub.2O.sub.3. In embodiments, the glass composition and resultant glass article may comprise greater than or equal to 16 mol % and less than or equal to 28 mol % Al.sub.2O.sub.3. In embodiments, the concentration of Al.sub.2O.sub.3 in the glass composition and resultant glass article may be greater than or equal to 15 mol %, greater than or equal to 16 mol %, greater than or equal to 17 mol %, or even greater than or equal to 18 mol %. In embodiments, the concentration of Al.sub.2O.sub.3 in the glass composition and the resultant glass article may be less than or equal 30 mol %, less than or equal to 27 mol %, less than or equal to 24 mol %, or even less than or equal to 21 mol %. In embodiments, the concentration of Al.sub.2O.sub.3 in the glass composition and the resultant glass article may be greater than or equal 15 mol % and less than or equal to 30 mol %, greater than or equal 15 mol % and less than or equal to 27 mol %, greater than or equal 15 mol % and less than or equal to 24 mol %, greater than or equal 15 mol % and less than or equal to 21 mol %, greater than or equal 16 mol % and less than or equal to 30 mol %, greater than or equal 16 mol % and less than or equal to 27 mol %, greater than or equal 16 mol % and less than or equal to 24 mol %, greater than or equal 16 mol % and less than or equal to 21 mol %, greater than or equal 17 mol % and less than or equal to 30 mol %, greater than or equal 17 mol % and less than or equal to 27 mol %, greater than or equal 17 mol % and less than or equal to 24 mol %, greater than or equal 17 mol % and less than or equal to 21 mol %, greater than or equal 18 mol % and less than or equal to 30 mol %, greater than or equal 18 mol % and less than or equal to 27 mol %, greater than or equal 18 mol % and less than or equal to 24 mol %, or even greater than or equal 18 mol % and less than or equal to 21 mol %, or any and all sub-ranges formed from any of these endpoints.

[0167] In embodiments, the glass composition and resultant glass article may comprise greater than or equal to 17 mol % and less than or equal to 30 mol % Al.sub.2O.sub.3. In embodiments, the glass composition and resultant glass article may comprise greater than or equal to 17.5 mol % and less than or equal to 27 mol % Al.sub.2O.sub.3. In embodiments, the concentration of Al.sub.2O.sub.3 in the glass composition and resultant glass article may be greater than or equal to 17 mol %, greater than or equal to 17.5 mol %, or even greater than or equal to 18 mol %. In embodiments, the concentration of Al.sub.2O.sub.3 in the glass composition and the resultant glass article may be less than or equal 30 mol %, less than or equal to 27 mol %, less than or equal to 24 mol %, or even less than or equal to 21 mol %. In embodiments, the concentration of Al.sub.2O.sub.3 in the glass composition and the resultant glass article may be greater than or equal 17 mol % and less than or equal to 30 mol % Al.sub.2O.sub.3, greater than or equal to 17 mol % and less than or equal to 27 mol % Al.sub.2O.sub.3, greater than or equal to 17 mol % and less than or equal to 24 mol % Al.sub.2O.sub.3, greater than or equal to 17 mol % and less than or equal to 21 mol % Al.sub.2O.sub.3, greater than or equal to 17.5 mol % and less than or equal to 30 mol % Al.sub.2O.sub.3, greater than or equal to 17.5 mol % and less than or equal to 27 mol % Al.sub.2O.sub.3, greater than or equal to 17.5 mol % and less than or equal to 24 mol % Al.sub.2O.sub.3, greater than or equal to 17.5 mol % and less than or equal to 21 mol % Al.sub.2O.sub.3, greater than or equal to 18 mol % and less than or equal to 30 mol % Al.sub.2O.sub.3, greater than or equal to 18 mol % and less than or equal to 27 mol % Al.sub.2O.sub.3, greater than or equal to 18 mol % and less than or equal to 24 mol % Al.sub.2O.sub.3, or even greater than or equal to 18 mol % and less than or equal to 21 mol % Al.sub.2O.sub.3, or any and all sub-ranges formed from any of these endpoints.

[0168] As described hereinabove, the glass compositions and the resultant glass articles may contain alkali oxides, such as Na.sub.2O, to enable the ion exchangeability of the glass compositions. Na.sub.2O aids in the ion exchangeability of the glass composition. In embodiments, the glass composition and the resultant glass article may comprise greater than or equal to 5 mol % and less than or equal to 20 mol % Na.sub.2O. In embodiments, the glass composition and the resultant glass article may comprise greater than or equal to 7 mol % and less than or equal to 18 mol % Na.sub.2O. In embodiments, the concentration of Na.sub.2O in the glass composition and the resultant glass article may be greater than or equal to 5 mol %, greater than or equal to 6 mol %, greater than or equal to 7 mol %, greater than or equal to 8 mol %, or even greater than or equal to 9 mol %. In embodiments, the concentration of Na.sub.2O in the glass composition and the resultant glass article may be less than or equal to 20 mol %, less than or equal to 18 mol % or even less than or equal to 16 mol %. In embodiments, the concentration of Na.sub.2O in the glass composition and the resultant glass article may be greater than or equal to 5 mol % and less than or equal to 20 mol %, greater than or equal to 5 mol % and less than or equal to 18 mol %, greater than or equal to 5 mol % and less than or equal to 16 mol %, greater than or equal to 6 mol % and less than or equal to 20 mol %, greater than or equal to 6 mol % and less than or equal to 18 mol %, greater than or equal to 6 mol % and less than or equal to 16 mol %, greater than or equal to 7 mol % and less than or equal to 20 mol %, greater than or equal to 7 mol % and less than or equal to 18 mol %, greater than or equal to 7 mol % and less than or equal to 16 mol %, greater than or equal to 8 mol % and less than or equal to 20 mol %, greater than or equal to 8 mol % and less than or equal to 18 mol %, greater than or equal to 8 mol % and less than or equal to 16 mol %, greater than or equal to 9 mol % and less than or equal to 20 mol %, greater than or equal to 9 mol % and less than or equal to 18 mol %, or even greater than or equal to 9 mol % and less than or equal to 16 mol %, or any and all sub-ranges formed from any of these endpoints.

[0169] In embodiments, the glass composition and the resultant glass article may comprise greater than or equal to 5 mol % and less than or equal to 17 mol % Na.sub.2O. In embodiments, the concentration of Na.sub.2O in the glass composition and the resultant glass article may be greater than or equal to 5 mol %, greater than or equal to 6 mol %, greater than or equal to 7 mol %, greater than or equal to 8 mol %, or even greater than or equal to 9 mol %. In embodiments, the concentration of Na.sub.2O in the glass composition and the resultant glass article may be less than or equal to 20 mol %, less than or equal to 17 mol %, or even less than or equal to 15 mol %. In embodiments, the concentration of Na.sub.2O in the glass composition and the resultant glass article may be greater than or equal to 5 mol % and less than or equal to 20 mol %, greater than or equal to 5 mol % and less than or equal to 17 mol %, greater than or equal to 5 mol % and less than or equal to 15 mol %, greater than or equal to 6 mol % and less than or equal to 20 mol %, greater than or equal to 6 mol % and less than or equal to 17 mol %, greater than or equal to 6 mol % and less than or equal to 15 mol %, greater than or equal to 7 mol % and less than or equal to 20 mol %, greater than or equal to 7 mol % and less than or equal to 17 mol %, greater than or equal to 7 mol % and less than or equal to 15 mol %, greater than or equal to 8 mol % and less than or equal to 20 mol %, greater than or equal to 8 mol % and less than or equal to 17 mol %, greater than or equal to 8 mol % and less than or equal to 15 mol %, greater than or equal to 9 mol % and less than or equal to 20 mol %, greater than or equal to 9 mol % and less than or equal to 17 mol %, or even greater than or equal to 9 mol % and less than or equal to 15 mol %, or any and all sub-ranges formed from any of these endpoints.

[0170] In embodiments, the glass compositions and the resultant glass articles may contain other alkali oxides, such as K.sub.2O, to enable ion exchangeability, increase diffusivity, and lower liquidus temperature. In embodiments, the glass composition and the resultant glass article may comprise greater than or equal to 0 mol % and less than or equal to 2 mol % K.sub.2O. In embodiments, the concentration of K.sub.2O in the glass composition and the resultant glass article may be greater than or equal to 0 mol %, greater than or equal to 0.05 mol %, greater than or equal to 0.1 mol %, greater than or equal to 0.25 mol %, or even greater than or equal to 0.5 mol %. In embodiments, the concentration of K.sub.2O in the glass composition and the resultant glass article may be less than or equal to 2 mol %, less than or equal to 1.5 mol %, less than or equal to 1 mol %, or even less than or equal to 0.5 mol %. In embodiments, the concentration of K.sub.2O in the glass composition and the resultant glass article may be greater than or equal to 0 mol % and less than or equal to 2 mol %, greater than or equal to 0 mol % and less than or equal to 1.5 mol %, greater than or equal to 0 mol % and less than or equal to 1 mol %, greater than or equal to 0 mol % and less than or equal to 0.5 mol %, greater than or equal to 0.05 mol % and less than or equal to 2 mol %, greater than or equal to 0.05 mol % and less than or equal to 1.5 mol %, greater than or equal to 0.05 mol % and less than or equal to 1 mol %, greater than or equal to 0.05 mol % and less than or equal to 0.5 mol %, greater than or equal to 0.1 mol % and less than or equal to 2 mol %, greater than or equal to 0.1 mol % and less than or equal to 1.5 mol %, greater than or equal to 0.1 mol % and less than or equal to 1 mol %, greater than or equal to 0.1 mol % and less than or equal to 0.5 mol %, greater than or equal to 0.25 mol % and less than or equal to 2 mol %, greater than or equal to 0.25 mol % and less than or equal to 1.5 mol %, greater than or equal to 0.25 mol % and less than or equal to 1 mol %, greater than or equal to 0.25 mol % and less than or equal to 0.5 mol %, greater than or equal to 0.5 mol % and less than or equal to 2 mol %, greater than or equal to 0.5 mol % and less than or equal to 1.5 mol %, or even greater than or equal to 0.5 mol % and less than or equal to 1 mol %, or any and all sub-ranges formed from any of these endpoints. In embodiments, the glass composition and the resultant glass article may be free or substantially free of K.sub.2O.

[0171] As described hereinabove, the glass compositions and the resultant glass article may contain alkaline earth oxides (i.e., MgO and/or CaO) to increase Young's modulus and/or fracture toughness. RO is the sum (in mol %) of MgO and CaO present in the glass composition and the resultant glass article (i.e., RO=MgO (mol %)+CaO (mol %)). These alkaline earth oxides aid in lowering the viscosity of a glass composition, which enhances the formability. Compared to the alkali oxide components, the alkaline earth oxides increase the strain point, the Young's modulus, and the fracture toughness. The alkaline earth oxides may also improve the ion exchangeability. However, when too much of these alkali oxides are added to the glass composition, the diffusivity of sodium ions in the resultant glass article decreases which, in turn, adversely impacts the ion exchange performance (i.e., the ability to ion exchange) of the resultant glass article.

[0172] In embodiments, the concentration of RO in the glass composition and the resultant glass article may be greater 0 mol % and less than or equal to 30 mol %. In embodiments, the concentration of RO in the glass composition and the resultant glass article may be greater than or equal to 1 mol % and less than or equal to 25 mol %. In embodiments, the concentration of RO in the glass composition and the resultant glass article may be greater than 0 mol %, greater than or equal to 1 mol %, greater than or equal to 3 mol %, greater than or equal to 5 mol %, or even greater than or equal to 7 mol %. In embodiments, the concentration of RO in the glass composition and the resultant glass article may be less than or equal to 30 mol %, less than or equal to 20 mol %, or even less than or equal to 15 mol %. In embodiments, the concentration of RO in the glass composition and the resultant glass article may be greater than 0 mol % and less than or equal to 30 mol %, greater than 0 mol % and less than or equal to 20 mol %, greater than 0 mol % and less than or equal to 15 mol %, greater than or equal to 1 mol % and less than or equal to 30 mol %, greater than or equal to 1 mol % and less than or equal to 20 mol %, greater than or equal to 1 mol % and less than or equal to 15 mol %, greater than or equal to 3 mol % and less than or equal to 30 mol %, greater than or equal to 3 mol % and less than or equal to 20 mol %, greater than or equal to 3 mol % and less than or equal to 15 mol %, greater than or equal to 5 mol % and less than or equal to 30 mol %, greater than or equal to 5 mol % and less than or equal to 20 mol %, greater than or equal to 5 mol % and less than or equal to 15 mol %, greater than or equal to 7 mol % and less than or equal to 30 mol %, greater than or equal to 7 mol % and less than or equal to 20 mol %, or even greater than or equal to 7 mol % and less than or equal to 15 mol %, or any and all sub-ranges formed from any of these endpoints.

[0173] In embodiments, the glass composition and the resultant glass article may comprise greater than or equal to 0 mol % and less than or equal to 15 mol % MgO. In embodiments, the glass composition and the resultant glass article may comprise greater than 0 mol % and less than or equal to 13 mol % MgO. In embodiments, the concentration of MgO in the glass composition and the resultant glass article may be greater than or equal to 0 mol %, greater than or equal to 0.01 mol %, greater than or equal to 0.1 mol %, greater than or equal to 0.5 mol %, greater than or equal to 3 mol %, or even greater than or equal to 5 mol %. In embodiments, the concentration of MgO in the glass composition and the resultant glass article may be less than or equal to 15 mol %, less than or equal to 13 mol %, less than or equal to 10 mol %, less than or equal to 7 mol %, or even less than or equal to 5 mol %. In embodiments, the concentration of MgO in the glass composition and the resultant glass article may be greater than or equal to 0 mol % and less than or equal to 15 mol %, greater than or equal to 0 mol % and less than or equal to 13 mol %, greater than or equal to 0 mol % and less than or equal to 10 mol %, greater than or equal to 0 mol % and less than or equal to 7 mol %, greater than or equal to 0 mol % and less than or equal to 5 mol %, greater than or equal to 0.01 mol % and less than or equal to 15 mol %, greater than or equal to 0.01 mol % and less than or equal to 13 mol %, greater than or equal to 0.01 mol % and less than or equal to 10 mol %, greater than or equal to 0.01 mol % and less than or equal to 7 mol %, greater than or equal to 0.01 mol % and less than or equal to 5 mol %, greater than or equal to 0.1 mol % and less than or equal to 15 mol %, greater than or equal to 0.1 mol % and less than or equal to 13 mol %, greater than or equal to 0.1 mol % and less than or equal to 10 mol %, greater than or equal to 0.1 mol % and less than or equal to 7 mol %, greater than or equal to 0.1 mol % and less than or equal to 5 mol %, greater than or equal to 0.5 mol % and less than or equal to 15 mol %, greater than or equal to 0.5 mol % and less than or equal to 13 mol %, greater than or equal to 0.5 mol % and less than or equal to 10 mol %, greater than or equal to 0.5 mol % and less than or equal to 7 mol %, greater than or equal to 0.5 mol % and less than or equal to 5 mol %, greater than or equal to 3 mol % and less than or equal to 15 mol %, greater than or equal to 3 mol % and less than or equal to 13 mol %, greater than or equal to 3 mol % and less than or equal to 10 mol %, greater than or equal to 3 mol % and less than or equal to 7 mol %, greater than or equal to 3 mol % and less than or equal to 5 mol %, greater than or equal to 5 mol % and less than or equal to 15 mol %, greater than or equal to 5 mol % and less than or equal to 13 mol %, greater than or equal to 5 mol % and less than or equal to 10 mol %, or even greater than or equal to 5 mol % and less than or equal to 7 mol %, or any and all sub-ranges formed from any of these endpoints. In embodiments, the glass composition and the resultant glass article may be free or substantially free of MgO.

[0174] In embodiments, the glass composition and the resultant glass article may comprise greater than 0 mol % and less than or equal to 15 mol % MgO. In embodiments, the glass composition and the resultant glass article may comprise greater than or equal to 0.01 mol % and less than or equal to 13 mol % MgO.

[0175] In embodiments, the glass composition and the resultant glass article may comprise greater than or equal to 0 mol % and less than or equal to 15 mol % CaO. In embodiments, the glass composition and the resultant glass article may comprise greater than 0 mol % and less than or equal to 13 mol % CaO. In embodiments, the concentration of CaO in the glass composition and the resultant glass article may be greater than or equal to 0 mol %, greater than or equal to 0.01 mol %, greater than or equal to 0.1 mol %, greater than or equal to 0.5 mol %, greater than or equal to 1 mol %, greater than or equal to 3 mol %, or even greater than or equal to 5 mol %. In embodiments, the concentration of CaO in the glass composition and the resultant glass article may be less than or equal to 15 mol %, less than or equal to 13 mol %, less than or equal to 10 mol %, less than or equal to 7 mol %, or even less than or equal to 5 mol %. In embodiments, the concentration of CaO in the glass composition and the resultant glass article may be greater than or equal to 0 mol % and less than or equal to 15 mol %, greater than or equal to 0 mol % and less than or equal to 13 mol %, greater than or equal to 0 mol % and less than or equal to 10 mol %, greater than or equal to 0 mol % and less than or equal to 7 mol %, greater than or equal to 0 mol % and less than or equal to 5 mol %, greater than or equal to 0.01 mol % and less than or equal to 15 mol %, greater than or equal to 0.01 mol % and less than or equal to 13 mol %, greater than or equal to 0.01 mol % and less than or equal to 10 mol %, greater than or equal to 0.01 mol % and less than or equal to 7 mol %, greater than or equal to 0.01 mol % and less than or equal to 5 mol %, greater than or equal to 0.1 mol % and less than or equal to 15 mol %, greater than or equal to 0.1 mol % and less than or equal to 13 mol %, greater than or equal to 0.1 mol % and less than or equal to 10 mol %, greater than or equal to 0.1 mol % and less than or equal to 7 mol %, greater than or equal to 0.1 mol % and less than or equal to 5 mol %, greater than or equal to 0.5 mol % and less than or equal to 15 mol %, greater than or equal to 0.5 mol % and less than or equal to 13 mol %, greater than or equal to 0.5 mol % and less than or equal to 10 mol %, greater than or equal to 0.5 mol % and less than or equal to 7 mol %, greater than or equal to 0.5 mol % and less than or equal to 5 mol %, greater than or equal to 3 mol % and less than or equal to 15 mol %, greater than or equal to 3 mol % and less than or equal to 13 mol %, greater than or equal to 3 mol % and less than or equal to 10 mol %, greater than or equal to 3 mol % and less than or equal to 7 mol %, greater than or equal to 3 mol % and less than or equal to 5 mol %, greater than or equal to 5 mol % and less than or equal to 15 mol %, greater than or equal to 5 mol % and less than or equal to 13 mol %, greater than or equal to 5 mol % and less than or equal to 10 mol %, or even greater than or equal to 5 mol % and less than or equal to 7 mol %, or any and all sub-ranges formed from any of these endpoints. In embodiments, the glass composition and the resultant glass article may be free or substantially free of CaO.

[0176] In embodiments, the glass compositions and the resultant glass articles may contain other alkaline earth oxides, such as ZnO, SrO, and BaO.

[0177] In embodiments, the glass composition and the resultant glass article may comprise greater than or equal to 0 mol % and less than or equal to 15 mol % ZnO. In embodiments, the concentration of ZnO in the glass composition and the resultant glass article may be greater than or equal to 0 mol %, greater than or equal to 0.01 mol %, greater than or equal to 0.1 mol %, greater than or equal to 0.5 mol %, greater than or equal to 3 mol %, or even greater than or equal to 5 mol %. In embodiments, the concentration of ZnO in the glass composition and the resultant glass article may be less than or equal to 15 mol %, less than or equal to 13 mol %, less than or equal to 10 mol %, less than or equal to 7 mol %, or even less than or equal to 5 mol %. In embodiments, the concentration of ZnO in the glass composition and the resultant glass article may be greater than or equal to 0 mol % and less than or equal to 15 mol %, greater than or equal to 0 mol % and less than or equal to 13 mol %, greater than or equal to 0 mol % and less than or equal to 10 mol %, greater than or equal to 0 mol % and less than or equal to 7 mol %, greater than or equal to 0 mol % and less than or equal to 5 mol %, greater than or equal to 0.01 mol % and less than or equal to 15 mol %, greater than or equal to 0.01 mol % and less than or equal to 13 mol %, greater than or equal to 0.01 mol % and less than or equal to 10 mol %, greater than or equal to 0.01 mol % and less than or equal to 7 mol %, greater than or equal to 0.01 mol % and less than or equal to 5 mol %, greater than or equal to 0.1 mol % and less than or equal to 15 mol %, greater than or equal to 0.1 mol % and less than or equal to 13 mol %, greater than or equal to 0.1 mol % and less than or equal to 10 mol %, greater than or equal to 0.1 mol % and less than or equal to 7 mol %, greater than or equal to 0.1 mol % and less than or equal to 5 mol %, greater than or equal to 0.5 mol % and less than or equal to 15 mol %, greater than or equal to 0.5 mol % and less than or equal to 13 mol %, greater than or equal to 0.5 mol % and less than or equal to 10 mol %, greater than or equal to 0.5 mol % and less than or equal to 7 mol %, greater than or equal to 0.5 mol % and less than or equal to 5 mol %, greater than or equal to 3 mol % and less than or equal to 15 mol %, greater than or equal to 3 mol % and less than or equal to 13 mol %, greater than or equal to 3 mol % and less than or equal to 10 mol %, greater than or equal to 3 mol % and less than or equal to 7 mol %, greater than or equal to 3 mol % and less than or equal to 5 mol %, greater than or equal to 5 mol % and less than or equal to 15 mol %, greater than or equal to 5 mol % and less than or equal to 13 mol %, greater than or equal to 5 mol % and less than or equal to 10 mol %, or even greater than or equal to 5 mol % and less than or equal to 7 mol %, or any and all sub-ranges formed from any of these endpoints. In embodiments, the glass composition and the resultant glass article may be free or substantially free of ZnO.

[0178] In embodiments, the glass composition and the resultant glass article may comprise greater than or equal to 0 mol % and less than or equal to 2.5 mol % SrO. In embodiments, the concentration of SrO in the glass composition and the resultant glass article may be greater than or equal to 0 mol %, greater than or equal to 0.1 mol %, or even greater than or equal to 0.5 mol %. In embodiments, the concentration of SrO in the glass composition and the resultant glass article may be less than or equal to 2.5 mol %, less than or equal to 2 mol %, less than or equal to 1.5 mol %, or even less than or equal to 1 mol %. In embodiments, the concentration of SrO in the glass composition and the resultant glass article may be greater than or equal to 0 mol % and less than or equal to 2.5 mol %, greater than or equal to 0 mol % and less than or equal to 2 mol %, greater than or equal to 0 mol % and less than or equal to 1.5 mol %, greater than or equal to 0 mol % and less than or equal to 1 mol %, greater than or equal to 0.1 mol % and less than or equal to 2.5 mol %, greater than or equal to 0.1 mol % and less than or equal to 2 mol %, greater than or equal to 0.1 mol % and less than or equal to 1.5 mol %, greater than or equal to 0.1 mol % and less than or equal to 1 mol %, greater than or equal to 0.5 mol % and less than or equal to 2.5 mol %, greater than or equal to 0.5 mol % and less than or equal to 2 mol %, greater than or equal to 0.5 mol % and less than or equal to 1.5 mol %, or even greater than or equal to 0.5 mol % and less than or equal to 1 mol %, or any and all sub-ranges formed from any of these endpoints. In embodiments, the glass composition and the resultant glass article may be free or substantially free of SrO.

[0179] In embodiments, the glass composition and the resultant glass article may comprise greater than or equal to 0 mol % and less than or equal to 2.5 mol % BaO. In embodiments, the concentration of BaO in the glass composition and the resultant glass article may be greater than or equal to 0 mol %, greater than or equal to 0.1 mol %, or even greater than or equal to 0.5 mol %. In embodiments, the concentration of BaO in the glass composition and the resultant glass article may be less than or equal to 2.5 mol %, less than or equal to 2 mol %, less than or equal to 1.5 mol %, or even less than or equal to 1 mol %. In embodiments, the concentration of BaO in the glass composition and the resultant glass article may be greater than or equal to 0 mol % and less than or equal to 2.5 mol %, greater than or equal to 0 mol % and less than or equal to 2 mol %, greater than or equal to 0 mol % and less than or equal to 1.5 mol %, greater than or equal to 0 mol % and less than or equal to 1 mol %, greater than or equal to 0.1 mol % and less than or equal to 2.5 mol %, greater than or equal to 0.1 mol % and less than or equal to 2 mol %, greater than or equal to 0.1 mol % and less than or equal to 1.5 mol %, greater than or equal to 0.1 mol % and less than or equal to 1 mol %, greater than or equal to 0.5 mol % and less than or equal to 2.5 mol %, greater than or equal to 0.5 mol % and less than or equal to 2 mol %, greater than or equal to 0.5 mol % and less than or equal to 1.5 mol %, or even greater than or equal to 0.5 mol % and less than or equal to 1 mol %, or any and all sub-ranges formed from any of these endpoints. In embodiments, the glass composition and the resultant glass article may be free or substantially free of BaO.

[0180] The glass compositions and the resultant glass articles described herein are free or substantially free of Li (i.e., Li.sub.2O).

[0181] The total amount of Na.sub.2O+RO in the glass composition and the resultant glass article may be limited (i.e., less than or equal to 30 mol %) to prevent devitrification of the glass composition. In embodiments, the glass composition and the resultant glass article may be peraluminous (i.e., the amount of Al.sub.2O.sub.3 in the glass composition is greater than the sum of Na.sub.2O and RO), which may increase the fracture toughness of the glass composition such that the glass compositions are more resistant to damage and/or failure. In embodiments, the total amount of (Na.sub.2O+RO)/Al.sub.2O.sub.3 in the glass composition and the resultant glass article may be greater than or equal to 0.5, greater than or equal to 0.65, greater than or equal to 0.8, or even greater than or equal to 0.95. In embodiments, the total amount of (Na.sub.2O+RO)/Al.sub.2O.sub.3 in the glass composition may be less than or equal to 1.5, less than or equal to 1.4, or even less than or equal to 1.3. In embodiments, the total amount of (Na.sub.2O+RO)/Al.sub.2O.sub.3 in the glass composition may be greater than or equal to 0.5 and less than or equal to 1.5, greater than or equal to 0.5 and less than or equal to 1.4, greater than or equal to 0.5 and less than or equal to 1.3, greater than or equal to 0.65 and less than or equal to 1.5, greater than or equal to 0.65 and less than or equal to 1.4, greater than or equal to 0.65 and less than or equal to 1.3, greater than or equal to 0.8 and less than or equal to 1.5, greater than or equal to 0.8 and less than or equal to 1.4, greater than or equal to 0.8 and less than or equal to 1.3, greater than or equal to 0.95 and less than or equal to 1.5, greater than or equal to 0.95 and less than or equal to 1.4, or even greater than or equal to 0.95 and less than or equal to 1.3, or any and all sub-ranges formed from any of these endpoints.

[0182] In embodiments, the total amount of (Na.sub.2O+RO)/Al.sub.2O.sub.3 in the glass composition and the resultant glass article may be greater than or equal to 0.25, greater than or equal to 0.5, greater than or equal to 0.65, greater than or equal to 0.8, or even greater than or equal to 0.95. In embodiments, the total amount of (Na.sub.2O+RO)/Al.sub.2O.sub.3 in the glass composition and the resultant glass article may be less than or equal to 1.5, less than or equal to 1.4, or even less than or equal to 1.3. In embodiments, the total amount of (Na.sub.2O+RO)/Al.sub.2O.sub.3 in the glass composition and the resultant glass article may be greater than or equal to 0.25 and less than or equal to 1.5, greater than or equal to 0.25 and less than or equal to 1.4, greater than or equal to 0.25 and less than or equal to 1.3, greater than or equal to 0.5 and less than or equal to 1.5, greater than or equal to 0.5 and less than or equal to 1.4, greater than or equal to 0.5 and less than or equal to 1.3, greater than or equal to 0.65 and less than or equal to 1.5, greater than or equal to 0.65 and less than or equal to 1.4, greater than or equal to 0.65 and less than or equal to 1.3, greater than or equal to 0.8 and less than or equal to 1.5, greater than or equal to 0.8 and less than or equal to 1.4, greater than or equal to 0.8 and less than or equal to 1.3, greater than or equal to 0.95 and less than or equal to 1.5, greater than or equal to 0.95 and less than or equal to 1.4, or even greater than or equal to 0.95 and less than or equal to 1.3, or any and all sub-ranges formed from any of these endpoints.

[0183] Like SiO.sub.2 and Al.sub.2O.sub.3, P.sub.2O.sub.5 may be added to the glass composition and the resultant glass article as a network former, thereby reducing the meltability and formability of the glass composition. Thus, P.sub.2O.sub.5 may be added in amounts that do not overly decrease these properties. In other embodiments, P.sub.2O.sub.5 may be added to the glass composition and the resultant glass article to decrease the liquidus temperature, thereby improving formability. The addition of P.sub.2O.sub.5 may also increase the diffusivity of ions in the glass article during ion exchange treatment, thereby increasing the efficiency of these treatments. In embodiments, the glass composition and resultant glass article may comprise greater than 0 mol % and less than or equal to 5 mol % P.sub.2O.sub.5. In embodiments, the concentration of P.sub.2O.sub.5 in the glass composition and resultant glass article may be greater than or equal to 0 mol %, greater than or equal to 0.05 mol %, greater than or equal to 0.1 mol %, or even greater than or equal to 0.15 mol %. In embodiments, the concentration of P.sub.2O.sub.5 in the glass composition and resultant glass article may be less than or equal to 5 mol %, less than or equal to 4 mol %, less than or equal to 3 mol %, less than or equal to 2 mol %, or even less than or equal to 1 mol %. In embodiments, the concentration of P.sub.2O.sub.5 in the glass composition and resultant glass article may be greater than or equal to 0 mol % and less than or equal to 5 mol %, greater than or equal to 0 mol % and less than or equal to 4 mol %, greater than or equal to 0 mol % and less than or equal to 3 mol %, greater than or equal to 0 mol % and less than or equal to 2 mol %, greater than or equal to 0 mol % and less than or equal to 1 mol %, greater than or equal to 0.05 mol % and less than or equal to 5 mol %, greater than or equal to 0.05 mol % and less than or equal to 4 mol %, greater than or equal to 0.05 mol % and less than or equal to 3 mol %, greater than or equal to 0.05 mol % and less than or equal to 2 mol %, greater than or equal to 0.05 mol % and less than or equal to 1 mol %, greater than or equal to 0.1 mol % and less than or equal to 5 mol %, greater than or equal to 0.1 mol % and less than or equal to 4 mol %, greater than or equal to 0.1 mol % and less than or equal to 3 mol %, greater than or equal to 0.1 mol % and less than or equal to 2 mol %, greater than or equal to 0.1 mol % and less than or equal to 1 mol %, greater than or equal to 0.15 mol % and less than or equal to 5 mol %, greater than or equal to 0.15 mol % and less than or equal to 4 mol %, greater than or equal to 0.15 mol % and less than or equal to 3 mol %, or even greater than or equal to 0.15 mol % and less than or equal to 2 mol %, greater than or equal to 0.15 mol % and less than or equal to 1 mol %, or any and all sub-ranges formed from any of these endpoints. In embodiments, the glass composition and the resultant glass article may be free or substantially free of P.sub.2O.sub.5.

[0184] In embodiments, the concentration of P.sub.2O.sub.5 in the glass composition and resultant glass article may be greater than or equal to 0 mol %, greater than or equal to 0.1 mol %, greater than or equal to 0.2 mol %, or even greater than or equal to 0.4 mol %. In embodiments, the concentration of P.sub.2O.sub.5 in the glass composition and resultant glass article may be less than or equal to 5 mol %, less than or equal to 4 mol %, less than or equal to 3 mol %, less than or equal to 2 mol %, or even less than or equal to 1 mol %. In embodiments, the concentration of P.sub.2O.sub.5 in the glass composition and resultant glass article may be greater than or equal to 0 mol % and less than or equal to 5 mol %, greater than or equal to 0 mol % and less than or equal to 4 mol %, greater than or equal to 0 mol % and less than or equal to 3 mol %, greater than or equal to 0 mol % and less than or equal to 2 mol %, greater than or equal to 0 mol % and less than or equal to 1 mol %, greater than or equal to 0.1 mol % and less than or equal to 5 mol %, greater than or equal to 0.1 mol % and less than or equal to 4 mol %, greater than or equal to 0.1 mol % and less than or equal to 3 mol %, greater than or equal to 0.1 mol % and less than or equal to 2 mol %, greater than or equal to 0.1 mol % and less than or equal to 1 mol %, greater than or equal to 0.2 mol % and less than or equal to 5 mol %, greater than or equal to 0.2 mol % and less than or equal to 4 mol %, greater than or equal to 0.2 mol % and less than or equal to 3 mol %, greater than or equal to 0.2 mol % and less than or equal to 2 mol %, greater than or equal to 0.2 mol % and less than or equal to 1 mol %, greater than or equal to 0.4 mol % and less than or equal to 5 mol %, greater than or equal to 0.4 mol % and less than or equal to 4 mol %, greater than or equal to 0.4 mol % and less than or equal to 3 mol %, or even greater than or equal to 0.4 mol % and less than or equal to 2 mol %, or even greater than or equal to 0.4 mol % and less than or equal to 1 mol %, or any and all sub-ranges formed from any of these endpoints.

[0185] The glass compositions and resultant glass articles described herein may include Y.sub.2O.sub.3 to increase the Young's modulus and/or fracture toughness of the glass compositions and the resultant glass articles described herein. In embodiments, the glass composition and the resultant glass article may comprise greater than 0 mol % and less than or equal to 10 mol % Y.sub.2O.sub.3. In embodiments, the concentration of Y.sub.2O.sub.3 in the glass composition and the resultant glass article may be greater than or equal to 0 mol %, greater than or equal to 0.1 mol %, greater than or equal to 0.5 mol %, or even greater than or equal to 1 mol %. In embodiments, the concentration of Y.sub.2O.sub.3 in the glass composition and the resultant glass article may be less than or equal to 10 mol %, less than or equal to 7 mol %, less than or equal to 5 mol %, or even less than or equal to 3 mol %. In embodiments, the concentration of Y.sub.2O.sub.3 in the glass composition and the resultant glass article may be greater than or equal to 0 mol % and less than or equal to 10 mol %, greater than or equal to 0 mol % and less than or equal to 7 mol %, greater than or equal to 0 mol % and less than or equal to 5 mol %, greater than or equal to 0 mol % and less than or equal to 3 mol %, greater than or equal to 0.1 mol % and less than or equal to 10 mol %, greater than or equal to 0.1 mol % and less than or equal to 7 mol %, greater than or equal to 0.1 mol % and less than or equal to 5 mol %, greater than or equal to 0.1 mol % and less than or equal to 3 mol %, greater than or equal to 0.5 mol % and less than or equal to 10 mol %, greater than or equal to 0.5 mol % and less than or equal to 7 mol %, greater than or equal to 0.5 mol % and less than or equal to 5 mol %, greater than or equal to 0.5 mol % and less than or equal to 3 mol %, greater than or equal to 1 mol % and less than or equal to 10 mol %, greater than or equal to 1 mol % and less than or equal to 7 mol %, greater than or equal to 1 mol % and less than or equal to 5 mol %, or even greater than or equal to 1 mol % and less than or equal to 3 mol %, or any and all sub-ranges formed from any of these endpoints. In embodiments, the glass composition and the resultant glass article may be free or substantially free of Y.sub.2O.sub.3.

[0186] The glass compositions and resultant glass articles described herein may include ZrO.sub.2 to increase the Young's modulus and/or fracture toughness of the glass compositions and the resultant glass articles described herein. In embodiments, the concentration of ZrO.sub.2 in the glass composition may be greater than 0 mol % and less than or equal to 5 mol %. In embodiments, the concentration of ZrO.sub.2 in the glass composition and the resultant glass article may be greater than or equal to 0 mol %, greater than or equal to 0.05 mol %, greater than or equal to 0.1 mol %, greater than or equal to 0.15 mol %, or even greater than or equal to 0.2 mol %. In embodiments, the concentration of ZrO.sub.2 in the glass composition may be less than or equal to 5 mol %, less than or equal to 4 mol %, less than or equal to 3 mol %, less than or equal to 2 mol %, or even less than or equal to 1 mol %. In embodiments, the concentration of ZrO.sub.2 in the glass composition may be greater than or equal to 0 mol % and less than or equal to 5 mol %, greater than or equal to 0 mol % and less than or equal to 4 mol %, greater than or equal to 0 mol % and less than or equal to 3 mol %, greater than or equal to 0 mol % and less than or equal to 2 mol %, greater than or equal to 0 mol % and less than or equal to 1 mol %, greater than or equal to 0.05 mol % and less than or equal to 5 mol %, greater than or equal to 0.05 mol % and less than or equal to 4 mol %, greater than or equal to 0.05 mol % and less than or equal to 3 mol %, greater than or equal to 0.05 mol % and less than or equal to 2 mol %, greater than or equal to 0.05 mol % and less than or equal to 1 mol %, greater than or equal to 0.1 mol % and less than or equal to 5 mol %, greater than or equal to 0.1 mol % and less than or equal to 4 mol %, greater than or equal to 0.1 mol % and less than or equal to 3 mol %, greater than or equal to 0.1 mol % and less than or equal to 2 mol %, greater than or equal to 0.1 mol % and less than or equal to 1 mol %, greater than or equal to 0.15 mol % and less than or equal to 5 mol %, greater than or equal to 0.15 mol % and less than or equal to 4 mol %, greater than or equal to 0.15 mol % and less than or equal to 3 mol %, greater than or equal to 0.15 mol % and less than or equal to 2 mol %, greater than or equal to 0.15 mol % and less than or equal to 1 mol %, greater than or equal to 0.2 mol % and less than or equal to 5 mol %, greater than or equal to 0.2 mol % and less than or equal to 4 mol %, greater than or equal to 0.2 mol % and less than or equal to 3 mol %, greater than or equal to 0.2 mol % and less than or equal to 2 mol %, or even greater than or equal to 0.2 mol % and less than or equal to 1 mol %, or any and all sub-ranges formed from any of these endpoints. In embodiments, the glass composition may be substantially free of ZrO.sub.2.

[0187] The glass compositions and resultant glass articles described herein may include TiO.sub.2. While not wishing to be bound by theory, TiO.sub.2 may increase the Young's modulus and/or fracture toughness of the glass compositions and the resultant glass articles described herein. In embodiments, the glass compositions and the resultant glass article may comprise greater than or equal to 0 mol % and less than or equal to 2 mol % TiO.sub.2. In embodiments, the concentration of TiO.sub.2 in the glass composition and the resultant glass article may be greater than or equal to 0 mol %, greater than or equal to 0.05 mol %, greater than or equal to 0.1 mol %, greater than or equal to 0.25 mol %, or even greater than or equal to 0.5 mol %. In embodiments, the concentration of TiO.sub.2 in the glass composition and the resultant glass article may be less than or equal to 2 mol %, less than or equal to 1.5 mol %, less than or equal to 1 mol %, or even less than or equal to 0.5 mol %. In embodiments, the concentration of TiO.sub.2 in the glass composition and the resultant glass article may be greater than or equal to 0 mol % and less than or equal to 2 mol %, greater than or equal to 0 mol % and less than or equal to 1.5 mol %, greater than or equal to 0 mol % and less than or equal to 1 mol %, greater than or equal to 0 mol % and less than or equal to 0.5 mol %, greater than or equal to 0.05 mol % and less than or equal to 2 mol %, greater than or equal to 0.05 mol % and less than or equal to 1.5 mol %, greater than or equal to 0.05 mol % and less than or equal to 1 mol %, greater than or equal to 0.05 mol % and less than or equal to 0.5 mol %, greater than or equal to 0.1 mol % and less than or equal to 2 mol %, greater than or equal to 0.1 mol % and less than or equal to 1.5 mol %, greater than or equal to 0.1 mol % and less than or equal to 1 mol %, greater than or equal to 0.1 mol % and less than or equal to 0.5 mol %, greater than or equal to 0.25 mol % and less than or equal to 2 mol %, greater than or equal to 0.25 mol % and less than or equal to 1.5 mol %, greater than or equal to 0.25 mol % and less than or equal to 1 mol %, greater than or equal to 0.25 mol % and less than or equal to 0.5 mol %, greater than or equal to 0.5 mol % and less than or equal to 2 mol %, greater than or equal to 0.5 mol % and less than or equal to 1.5 mol %, or even greater than or equal to 0.5 mol % and less than or equal to 1 mol %, or any and all sub-ranges formed from any of these endpoints. In embodiments, the glass composition and the resultant glass article may be free or substantially free of TiO.sub.2.

[0188] In embodiments, the glass compositions described herein may further include one or more fining agents. In embodiments, the fining agents may include, for example, SnO.sub.2. In embodiments, the concentration of SnO.sub.2 in the glass composition may be greater than 0 mol % and less than or equal to 1 mol %. In embodiments, the concentration of SnO.sub.2 in the glass composition and the resultant glass article may be greater than or equal to 0 mol %, greater than or equal to 0.05 mol %, or even greater than or equal to 0.1 mol %. In embodiments, the concentration of SnO.sub.2 in the glass composition may be less than or equal to 1 mol %, less than or equal to 0.5 mol %, less than or equal to 0.4 mol %, less than or equal to 0.3 mol %, or even less than or equal to 0.2 mol %. In embodiments, the concentration of SnO.sub.2 in the glass composition may be greater than or equal to 0 mol % and less than or equal to 1 mol %, greater than or equal to 0 mol % and less than or equal to 0.5 mol %, greater than or equal to 0 mol % and less than or equal to 0.4 mol %, greater than or equal to 0 mol % and less than or equal to 0.3 mol %, greater than or equal to 0 mol % and less than or equal to 0.2 mol %, greater than or equal to 0.05 mol % and less than or equal to 1 mol %, greater than or equal to 0.05 mol % and less than or equal to 0.5 mol %, greater than or equal to 0.05 mol % and less than or equal to 0.4 mol %, greater than or equal to 0.05 mol % and less than or equal to 0.3 mol %, greater than or equal to 0.05 mol % and less than or equal to 0.2 mol %, greater than or equal to 0.1 mol % and less than or equal to 1 mol %, greater than or equal to 0.1 mol % and less than or equal to 0.5 mol %, greater than or equal to 0.1 mol % and less than or equal to 0.4 mol %, greater than or equal to 0.1 mol % and less than or equal to 0.3 mol %, or even greater than or equal to 0.1 mol % and less than or equal to 0.2 mol %, or any and all sub-ranges formed from any of these endpoints. In embodiments, the glass composition may be substantially free of SnO.sub.2.

[0189] In embodiments, the glass compositions and resultant glass articles described herein may be free or substantially free of Fe.sub.2O.sub.3. In embodiments, the glass compositions and resultant glass articles described herein may be free or substantially free of Er.sub.2O.sub.3.

[0190] In embodiments, the glass composition may comprise: greater than or equal to 50 mol % and less than or equal to 70 mol % SiO.sub.2; greater than or equal to 15 mol % and less than or equal to 30 mol % Al.sub.2O.sub.3; greater than or equal to 5 mol % and less than or equal to 20 mol % Na.sub.2O; greater than or equal to 0 mol % and less than or equal to 15 mol % MgO; and greater than or equal to 0 mol % and less than or equal to 15 mol % CaO, wherein the glass composition is free or substantially free of Li; and RO is greater than 0 mol % and less than or equal to 30 mol %, wherein RO is the sum of MgO and CaO.

[0191] In embodiments, the glass composition may comprise: greater than or equal to 50 mol % and less than or equal to 70 mol % SiO.sub.2; greater than or equal to 16 mol % and less than or equal to 28 mol % Al.sub.2O.sub.3; greater than or equal to 7 mol % and less than or equal to 18 mol % Na.sub.2O; greater than or equal to 0 mol % and less than or equal to 13 mol % MgO; and greater than or equal to 0 mol % and less than or equal to 13 mol % CaO, wherein the glass composition is free or substantially free of Li; and RO is greater than 1 mol % and less than or equal to 25 mol %, wherein RO is the sum of MgO and CaO

[0192] In embodiments, the glass composition may comprise: greater than or equal to 50 mol % and less than or equal to 70 mol % SiO.sub.2; greater than or equal to 16 mol % and less than or equal to 28 mol % Al.sub.2O.sub.3; greater than or equal to 7 mol % and less than or equal to 18 mol % Na.sub.2O; greater than or equal to 0 mol % and less than or equal to 15 mol % MgO; and greater than or equal to 0 mol % and less than or equal to 15 mol % CaO, wherein the glass composition is free or substantially free of Li; and RO is greater than 0 mol % and less than or equal to 30 mol %, wherein RO is the sum of MgO and CaO.

[0193] In embodiments, the glass composition may comprise: greater than or equal to 50 mol % and less than or equal to 70 mol % SiO.sub.2; greater than or equal to 18 mol % and less than or equal to 26 mol % Al.sub.2O.sub.3; greater than or equal to 9 mol % and less than or equal to 16 mol % Na.sub.2O; greater than or equal to 0 mol % and less than or equal to 15 mol % MgO; and greater than or equal to 0 mol % and less than or equal to 15 mol % CaO, wherein the glass composition is free or substantially free of Li; and RO is greater than 0 mol % and less than or equal to 30 mol %, wherein RO is the sum of MgO and CaO.

[0194] In embodiments, the glass composition may comprise: greater than or equal to 50 mol % and less than or equal to 70 mol % SiO.sub.2; greater than or equal to 17 mol % and less than or equal to 30 mol % Al.sub.2O.sub.3; greater than or equal to 5 mol % and less than or equal to 20 mol % Na.sub.2O; greater than 0 mol % and less than or equal to 15 mol % MgO; greater than or equal to 0 mol % and less than or equal to 15 mol % CaO; and greater than or equal to 0 mol % and less than or equal to 5 mol % P.sub.2O.sub.5, wherein the glass composition is free or substantially free of Li and Fe.sub.2O.sub.3; and RO is greater than 0 mol % and less than or equal to 30 mol %, wherein RO is the sum of MgO and CaO.

[0195] In embodiments, the glass composition may comprise: greater than or equal to 50 mol % and less than or equal to 70 mol % SiO.sub.2; greater than or equal to 17 mol % and less than or equal to 30 mol % Al.sub.2O.sub.3; greater than or equal to 5 mol % and less than or equal to 20 mol % Na.sub.2O; greater than 0 mol % and less than or equal to 15 mol % MgO; greater than or equal to 0 mol % and less than or equal to 15 mol % CaO; and greater than or equal to 0.1 mol % and less than or equal to 5 mol % P.sub.2O.sub.5, wherein the glass composition is free or substantially free of Li and Fe.sub.2O.sub.3; and RO is greater than 0 mol % and less than or equal to 30 mol %, wherein RO is the sum of MgO and CaO.

[0196] In embodiments, the glass composition may comprise: greater than or equal to 50 mol % and less than or equal to 70 mol % SiO.sub.2; greater than or equal to 17 mol % and less than or equal to 30 mol % Al.sub.2O.sub.3; greater than or equal to 5 mol % and less than or equal to 17 mol % Na.sub.2O; greater than 0 mol % and less than or equal to 15 mol % MgO; greater than or equal to 0 mol % and less than or equal to 15 mol % CaO; and greater than or equal to 0 mol % and less than or equal to 5 mol % P.sub.2O.sub.5, wherein the glass composition is free or substantially free of Li and Fe.sub.2O.sub.3; and RO is greater than 0 mol % and less than or equal to 30 mol %, wherein RO is the sum of MgO and CaO.

[0197] In embodiments, the glass composition may comprise: greater than or equal to 50 mol % and less than or equal to 70 mol % SiO.sub.2; greater than or equal to 17 mol % and less than or equal to 30 mol % Al.sub.2O.sub.3; greater than or equal to 5 mol % and less than or equal to 20 mol % Na.sub.2O; greater than 0 mol % and less than or equal to 15 mol % MgO; greater than or equal to 0 mol % and less than or equal to 15 mol % CaO; and greater than or equal to 0 mol % and less than or equal to 5 mol % P.sub.2O.sub.5, wherein the glass composition is free or substantially free of Li, Fe.sub.2O.sub.3, and Er.sub.2O.sub.3; and RO is greater than 0 mol % and less than or equal to 30 mol %, wherein RO is the sum of MgO and CaO.

[0198] The articles formed from the glass compositions described herein may be any suitable shape or thickness, which may vary depending on the particular application for use of the glass composition. Glass sheet embodiments may have a thickness greater than or equal to 30 ?m, greater than or equal to 50 ?m, greater than or equal to 100 ?m, greater than or equal to 250 ?m, greater than or equal to 500 ?m, greater than or equal to 750 ?m, or even greater than or equal to 1 mm. In embodiments, the glass sheet embodiments may have a thickness less than or equal to 6 mm, less than or equal to 5 mm, less than or equal to 4 mm, less than or equal to 3 mm, or even less than or equal to 2 mm. In embodiments, the glass sheet embodiments may have a thickness greater than or equal to 30 ?m and less than or equal to 6 mm, greater than or equal to 30 ?m and less than or equal to 5 mm, greater than or equal to 30 ?m and less than or equal to 4 mm, greater than or equal to 30 ?m and less than or equal to 3 mm, greater than or equal to 30 ?m and less than or equal to 2 mm, greater than or equal to 50 ?m and less than or equal to 6 mm, greater than or equal to 50 ?m and less than or equal to 5 mm, greater than or equal to 50 ?m and less than or equal to 4 mm, greater than or equal to 50 ?m and less than or equal to 3 mm, greater than or equal to 50 ?m and less than or equal to 2 mm, greater than or equal to 100 ?m and less than or equal to 6 mm, greater than or equal to 100 ?m and less than or equal to 5 mm, greater than or equal to 100 ?m and less than or equal to 4 mm, greater than or equal to 100 ?m and less than or equal to 3 mm, greater than or equal to 100 ?m and less than or equal to 2 mm, greater than or equal to 250 ?m and less than or equal to 6 mm, greater than or equal to 250 ?m and less than or equal to 5 mm, greater than or equal to 250 ?m and less than or equal to 4 mm, greater than or equal to 250 ?m and less than or equal to 3 mm, greater than or equal to 250 ?m and less than or equal to 2 mm, greater than or equal to 500 ?m and less than or equal to 6 mm, greater than or equal to 500 ?m and less than or equal to 5 mm, greater than or equal to 500 ?m and less than or equal to 4 mm, greater than or equal to 500 ?m and less than or equal to 3 mm, greater than or equal to 500 ?m and less than or equal to 2 mm, greater than or equal to 750 ?m and less than or equal to 6 mm, greater than or equal to 750 ?m and less than or equal to 5 mm, greater than or equal to 750 ?m and less than or equal to 4 mm, greater than or equal to 750 ?m and less than or equal to 3 mm, greater than or equal to 750 ?m and less than or equal to 2 mm, greater than or equal to 1 mm and less than or equal to 6 mm, greater than or equal to 1 mm and less than or equal to 5 mm, greater than or equal to 1 mm and less than or equal to 4 mm, greater than or equal to 1 mm and less than or equal to 3 mm, or even greater than or equal to 1 mm and less than or equal to 2 mm, or any and all sub-ranges formed from any of these endpoints.

[0199] As discussed hereinabove, the glass compositions and the resultant glass articles described herein may have increased fracture toughness such that the glass compositions and the resultant glass articles are more resistant to damage. In embodiments, the glass composition and the resultant glass article may have a K.sub.Ic fracture toughness greater than or equal to 0.75 MPa.Math.m.sup.1/2, greater than or equal to 0.80 MPa.Math.m.sup.1/2, greater than or equal to 0.85 MPa.Math.m.sup.1/2, or even greater than or equal to 0.90 MPa.Math.m.sup.1/2.

[0200] In embodiments, the glass composition and the resultant glass article may have a density greater than or equal to 2.30 g/cm.sup.3, greater than or equal to 2.40 g/cm.sup.3, or even greater than or equal to 2.45 g/cm.sup.3. In embodiments, the glass composition and the resultant glass article may have a density less than or equal to 2.90 g/cm.sup.3, less than or equal to 2.80 g/cm.sup.3, or even less than or equal to 2.75 g/cm.sup.3. In embodiments, the glass composition and the resultant glass article may have a density greater than or equal to 2.30 g/cm.sup.3 and less than or equal to 2.90 g/cm.sup.3, greater than or equal to 2.30 g/cm.sup.3 and less than or equal to 2.80 g/cm.sup.3, greater than or equal to 2.30 g/cm.sup.3 and less than or equal to 2.75 g/cm.sup.3, greater than or equal to 2.40 g/cm.sup.3 and less than or equal to 2.90 g/cm.sup.3, greater than or equal to 2.40 g/cm.sup.3 and less than or equal to 2.80 g/cm.sup.3, greater than or equal to 2.40 g/cm.sup.3 and less than or equal to 2.75 g/cm.sup.3, greater than or equal to 2.45 g/cm.sup.3 and less than or equal to 2.90 g/cm.sup.3, greater than or equal to 2.45 g/cm.sup.3 and less than or equal to 2.80 g/cm.sup.3, or even greater than or equal to 2.45 g/cm.sup.3 and less than or equal to 2.75 g/cm.sup.3, or any and all sub-ranges formed from any of these endpoints.

[0201] As described in further detail below, exchanging Na.sup.+ ions in the resultant glass article with K.sup.+ ions in a molten salt bath is relatively slow. Accordingly, it may be desirable to increase the ion exchange rate by ion exchanging the glass article at relatively high temperatures (i.e., greater than or equal to 500? C.). However, ion exchanging the glass article at relatively high temperature may result in stress relaxation, if the ion exchanged article has a strain point that is within about 100? C. of the ion exchange process temperatures. To prevent an undesirable amount of stress relaxation, the glass composition and resultant glass articles herein have a relatively high strain point (i.e., greater than or equal to 600? C.). In embodiments, the glass composition and the resultant glass article may have a strain point greater than or equal to 600? C., greater than or equal to 650? C., or even greater than or equal to 700? C. In embodiments, the glass composition and the resultant glass article may have a strain point less than or equal to 800? C., less than or equal to 775? C., or even less than or equal to 750? C. In embodiments, the glass composition and the resultant glass article may have a strain point greater than or equal to 600? C. and less than or equal to 800? C., greater than or equal to 600? C. and less than or equal to 775? C., greater than or equal to 600? C. and less than or equal to 750? C., greater than or equal to 650? C. and less than or equal to 800? C., greater than or equal to 650? C. and less than or equal to 775? C., greater than or equal to 650? C. and less than or equal to 750? C., greater than or equal to 700? C. and less than or equal to 800? C., greater than or equal to 700? C. and less than or equal to 775? C., or even greater than or equal to 700? C. and less than or equal to 750? C., or any and all sub-ranges formed from any of these endpoints.

[0202] In embodiments, the glass composition and the resultant glass article may have an annealing point greater than or equal to 700? C. or even greater than or equal to 725? C. In embodiments, the glass composition and the resultant glass article may have an annealing point less than or equal to 825? C. or even less than or equal to 800? C. In embodiments, the glass composition and the resultant glass article may have an annealing point greater than or equal to 700? C. and less than or equal to 825? C., greater than or equal to 700? C. and less than or equal to 800? C., greater than or equal to 725? C. and less than or equal to 825? C., or even greater than or equal to 725? C. and less than or equal to 800? C., or any and all sub-ranges formed from any of these endpoints.

[0203] In embodiments, the glass composition and the resultant glass article may have a Young's modulus greater than or equal to 60 GPa, greater than or equal to 65 GPa, or even greater than or equal to 70 GPa. In embodiments, the glass composition and the resultant glass article may have a Young's modulus less than or equal to 110 GPa, less than or equal to 100 GPa, or even less than or equal to 90 GPa. In embodiments, the glass composition and the resultant glass article may have a Young's modulus greater than or equal to 60 GPa and less than or equal to 110 GPa, greater than or equal to 60 GPa and less than or equal to 100 GPa, greater than or equal to 60 GPa and less than or equal to 90 GPa, greater than or equal to 65 GPa and less than or equal to 110 GPa, greater than or equal to 65 GPa and less than or equal to 100 GPa, greater than or equal to 65 GPa and less than or equal to 90 GPa, greater than or equal to 70 GPa and less than or equal to 110 GPa, greater than or equal to 70 GPa and less than or equal to 100 GPa, or even greater than or equal to 70 GPa and less than or equal to 90 GPa, or any and all sub-ranges formed from any of these endpoints.

[0204] In embodiments, the glass composition and the resultant glass article may have a shear modulus greater than or equal to 20 GPa, greater than or equal to 25 GPa, or even greater than or equal to 30 GPa. In embodiments, the glass composition and the resultant glass article may have a shear modulus less than or equal to 50 GPa, less than or equal to 45 GPa, or even less than or equal to 40 GPa. In embodiments, the glass composition and the resultant glass article may have a shear modulus greater than or equal to 20 GPa and less than or equal to 50 GPa, greater than or equal to 20 GPa and less than or equal to 45 GPa, greater than or equal to 20 GPa and less than or equal to 40 GPa, greater than or equal to 25 GPa and less than or equal to 50 GPa, greater than or equal to 25 GPa and less than or equal to 45 GPa, greater than or equal to 25 GPa and less than or equal to 40 GPa, greater than or equal to 30 GPa and less than or equal to 50 GPa, greater than or equal to 30 GPa and less than or equal to 45 GPa, or even greater than or equal to 30 GPa and less than or equal to 40 GPa, or any and all sub-ranges formed from any of these endpoints.

[0205] In embodiments, the glass compositions and the resultant glass articles described herein may have a relatively high Poisson's ratio, which increases the fracture energy such that the glass compositions are more resistant to damage. In embodiments, the glass composition and the resultant glass article may have a Poisson's ratio greater than or equal to 0.19, greater than or equal to 0.20, or even greater than or equal to 0.21. In embodiments, the glass composition and the resultant glass article may have a Poisson's ratio less than or equal to 0.26, less than or equal to 0.25, or even less than or equal to 0.24. In embodiments, the glass composition and the resultant glass article may have a Poisson's ratio greater than or equal to 0.19 and less than or equal to 0.26, greater than or equal to 0.19 and less than or equal to 0.25, greater than or equal to 0.19 and less than or equal to 0.24, greater than or equal to 0.20 and less than or equal to 0.26, greater than or equal to 0.20 and less than or equal to 0.25, greater than or equal to 0.20 and less than or equal to 0.24, greater than or equal to 0.21 and less than or equal to 0.26, greater than or equal to 0.21 and less than or equal to 0.25, or even greater than or equal to 0.21 and less than or equal to 0.24, or any and all sub-ranges formed from any of these endpoints.

[0206] In embodiments, the glass composition and the resultant glass article may have a refractive index greater than or equal to 1.4, greater than or equal to 1.45, or even greater than or equal to 1.5. In embodiments, the glass composition and the resultant glass article may have a refractive index less than or equal to 1.7 or even less than or equal to 1.6. In embodiments, the glass composition and the resultant glass article may have a refractive index greater than or equal to 1.4 and less than or equal to 1.7, greater than or equal to 1.4 and less than or equal to 1.6, greater than or equal to 1.45 and less than or equal to 1.7, greater than or equal to 1.45 and less than or equal to 1.6, greater than or equal to 1.5 and less than or equal to 1.7, or even greater than or equal to 1.5 and less than or equal to 1.6, or any and all sub-ranges formed from any of these endpoints.

[0207] In embodiments, the glass composition and the resultant glass article may have a stress optical coefficient (SOC) greater than or equal to 2.40 nm/mm/MPa or even greater than or equal to 2.55 nm/mm/MPa. In embodiments, the glass composition and the resultant glass article may have a SOC less than or equal to 3.50 nm/mm/MPa or even less than or equal to 3.25 nm/mm/MPa. In embodiments, the glass composition and the resultant glass article may have a SOC greater than or equal to 2.40 nm/mm/MPa and less than or equal to 3.50 nm/mm/MPa, greater than or equal to 2.40 nm/mm/MPa and less than or equal to 3.25 nm/mm/MPa, greater than or equal to 2.55 nm/mm/MPa and less than or equal to 3.50 nm/mm/MPa, or even greater than or equal to 2.55 nm/mm/MPa and less than or equal to 3.25 nm/mm/MPa, or any and all sub-ranges formed from any of these endpoints.

[0208] In embodiments, the glass composition and the resultant glass article may have a liquidus viscosity greater than or equal to 0.5 kP, greater than or equal to 1 kP, greater than or equal to 5 kP, greater than or equal to 10 kP, greater than or equal to 25 kP, or even greater than or equal to 35 kP. In embodiments, the glass composition and the resultant glass article may have a liquidus viscosity less than or equal to 300 kP, less than or equal to 250 kP, less than or equal to 200 kP, less than or equal to 150 kP, or even less than or equal to 100 kP. In embodiments, the glass composition and the resultant glass article may have a liquidus viscosity greater than or equal to 0.5 kP and less than or equal to 300 kP, greater than or equal to 0.5 kP and less than or equal to 250 kP, greater than or equal to 0.5 kP and less than or equal to 200 kP, greater than or equal to 0.5 kP and less than or equal to 150 kP, greater than or equal to 0.5 kP and less than or equal to 100 kP, greater than or equal to 1 kP and less than or equal to 300 kP, greater than or equal to 1 kP and less than or equal to 250 kP, greater than or equal to 1 kP and less than or equal to 200 kP, greater than or equal to 1 kP and less than or equal to 150 kP, greater than or equal to 1 kP and less than or equal to 100 kP, greater than or equal to 5 kP and less than or equal to 300 kP, greater than or equal to 5 kP and less than or equal to 250 kP, greater than or equal to 5 kP and less than or equal to 200 kP, greater than or equal to 5 kP and less than or equal to 150 kP, greater than or equal to 5 kP and less than or equal to 100 kP, greater than or equal to 10 kP and less than or equal to 300 kP, greater than or equal to 10 kP and less than or equal to 250 kP, greater than or equal to 10 kP and less than or equal to 200 kP, greater than or equal to 10 kP and less than or equal to 150 kP, greater than or equal to 10 kP and less than or equal to 100 kP, greater than or equal to 25 kP and less than or equal to 300 kP, greater than or equal to 25 kP and less than or equal to 250 kP, greater than or equal to 25 kP and less than or equal to 200 kP, greater than or equal to 25 kP and less than or equal to 150 kP, greater than or equal to 25 kP and less than or equal to 100 kP, greater than or equal to 35 kP and less than or equal to 300 kP, greater than or equal to 35 kP and less than or equal to 250 kP, greater than or equal to 35 kP and less than or equal to 200 kP, greater than or equal to 35 kP and less than or equal to 150 kP, or even greater than or equal to 35 kP and less than or equal to 100 kP, or any and all sub-ranges formed from any of these endpoints. These ranges of viscosities allow the glass compositions to be formed into sheets by a variety of different techniques including, without limitation, fusion forming, slot draw, floating, rolling, and other sheet-forming processes known to those in the art. However, it should be understood that other processes may be used for forming other articles (i.e., other than sheets).

[0209] In embodiments, the glass composition and the resultant glass article may have a K.sub.Ic fracture toughness greater than or equal to 0.75 MPa.Math.m.sup.1/2, a density greater than or equal to 2.30 g/cm.sup.3 and less than or equal to 2.90 g/cm.sup.3, an annealing point greater than or equal to 700? C. and less than or equal to 825? C., a Young's modulus greater than or equal to 60 GPa and less than or equal to 110 GPa, a shear modulus greater than or equal to 20 GPa and less than or equal to 50 GPa, a Poisson's ratio greater than or equal to 0.19 and less than or equal to 0.26, a refractive index greater than or equal to 1.4 and less than or equal to 1.7, a stress optical coefficient (SOC) greater than or equal to 2.40 nm/mm/MPa and less than or equal to 3.50 nm/mm/MPa, and a liquidus viscosity greater than or equal to 0.5 kP and less than or equal to 300 kP.

[0210] In embodiments, the process for making a glass article includes heat treating the glass composition as described herein at one or more preselected temperatures for one or more preselected times to melt the glass composition and cooling the glass composition. In embodiments, the heat treatment for making a glass article may include (i) heating a glass composition at a rate of 1-100? C./min to glass melting temperature; (ii) maintaining the glass composition at the glass melting temperature for a time greater than or equal to 4 hours and less than or equal to 100 hours to produce a glass article; and (iii) cooling the formed glass article to room temperature. In embodiments, the glass melting temperature may be greater than or equal to 1500? C. and less than or equal to 1700? C.

[0211] In embodiments, the glass compositions described herein are ion exchangeable to facilitate strengthening the glass article made from the glass compositions. In typical ion exchange processes, smaller metal ions in the glass article are replaced or exchanged with larger metal ions of the same valence within a layer that is close to the outer surface of the glass article. The replacement of smaller ions with larger ions creates a compressive stress within the layer of the glass article. In embodiments, the metal ions are monovalent metal ions (i.e., Na.sup.+, K.sup.+, and the like), and ion exchange is accomplished by immersing the glass article in a bath comprising at least one molten salt of the larger metal ion that is to replace the smaller metal ion in the glass article. Alternatively, other monovalent ions such as Ag.sup.+, Tl.sup.+, Cu.sup.+, and the like may be exchanged for monovalent ions. The ion exchange process or processes that are used to strengthen the glass article may include, but are not limited to, immersion in a single bath or multiple baths of like or different compositions with washing and/or annealing steps between immersions. In embodiments, there may be a first ion exchange step and a second ion exchange step.

[0212] Upon exposure to the glass article, the first ion exchange solution may, according to embodiments, be at a temperature greater than or equal to 500? C. and less than or equal to 700? C., greater than or equal to 505? C. and less than or equal to 675? C., greater than or equal to 510? C. and less than or equal to 650? C., greater than or equal to 515? C. and less than or equal to 625? C., greater than or equal to 520? C. and less than or equal to 620? C., greater than or equal to 525? C. and less than or equal to 615? C., or even greater than or equal to 530? C. and less than or equal to 610? C., or any and all sub-ranges between the foregoing values.

[0213] In embodiments, the glass article may be exposed to the first ion exchange solution for a duration greater than or equal to 0.25 hours and less than or equal to 32 hours, greater than or equal to 0.25 hours and less than or equal to 28 hours, greater than or equal to 0.25 hours and less than or equal to 24 hours, greater than or equal to 0.25 hours and less than or equal to 20 hours, greater than or equal to 0.25 hours and less than or equal to 16 hours, greater than or equal to 1 hour and less than or equal to 32 hours, greater than or equal to 1 hour and less than or equal to 28 hours, greater than or equal to 1 hour and less than or equal to 24 hours, greater than or equal to 1 hour and less than or equal to 20 hours, greater than or equal to 1 hour and less than or equal to 16 hours, greater than or equal to 4 hours and less than or equal to 32 hours, greater than or equal to 4 hours and less than or equal to 28 hours, or even greater than or equal to 4 hours and less than or equal to 24 hours, greater than or equal to 4 hours and less than or equal to 20 hours, or any and all sub-ranges formed from any of these endpoints.

[0214] Upon exposure to the glass article, the second ion exchange solution may, according to embodiments, be at a temperature greater than or equal to 350? C. and less than or equal to 700? C., greater than or equal to 360? C. and less than or equal to 675? C., greater than or equal to 370? C. and less than or equal to 650? C., greater than or equal to 360? C. and less than or equal to 625? C., greater than or equal to 370? C. and less than or equal to 620? C., greater than or equal to 375? C. and less than or equal to 615? C., greater than or equal to 400? C. and less than or equal to 610? C., greater than or equal to 410? C. and less than or equal to 600? C., greater than or equal to 420? C. and less than or equal to 590? C., greater than or equal to 430? C. and less than or equal to 575? C., or even greater than or equal to 440? C. and less than or equal to 550? C., or any and all sub-ranges between the foregoing values. In embodiments, the second ion exchange solution may be at a temperature greater than or equal to 350? C. and less than or equal to 530? C., greater than or equal to 360? C. and less than or equal to 510? C., greater than or equal to 370? C. and less than or equal to 490? C., greater than or equal to 360? C. and less than or equal to 470? C., greater than or equal to 370? C. and less than or equal to 450? C., greater than or equal to 375? C. and less than or equal to 430? C., or even greater than or equal to 400? C. and less than or equal to 410? C., or any and all sub-ranges between the foregoing values.

[0215] In embodiments, the glass article may be exposed to the second ion exchange solution for a duration greater than or equal to 0.25 hours and less than or equal to 32 hours, greater than or equal to 0.25 hours and less than or equal to 28 hours, greater than or equal to 0.25 hours and less than or equal to 24 hours, greater than or equal to 0.25 hours and less than or equal to 20 hours, greater than or equal to 0.25 hours and less than or equal to 16 hours, greater than or equal to 1 hour and less than or equal to 32 hours, greater than or equal to 1 hour and less than or equal to 28 hours, greater than or equal to 1 hour and less than or equal to 24 hours, greater than or equal to 1 hour and less than or equal to 20 hours, greater than or equal to 1 hour and less than or equal to 16 hours, greater than or equal to 4 hours and less than or equal to 32 hours, greater than or equal to 4 hours and less than or equal to 28 hours, or even greater than or equal to 4 hours and less than or equal to 24 hours, greater than or equal to 4 hours and less than or equal to 20 hours, or any and all sub-ranges formed from any of these endpoints. In embodiments, the glass article may be exposed to the second ion exchange solution for a duration greater than or equal to 0.05 hour and less than or equal to 32 hours, greater than or equal to 0.05 hour and less than or equal to 24 hours, greater than or equal to 0.05 hour and less than or equal to 18 hours, greater than or equal to 0.05 hour and less than or equal to 12 hours, greater than or equal to 0.05 hour and less than or equal to 6 hours, greater than or equal to 0.05 hour and less than or equal to 2 hours, greater than or equal to 0.1 hour and less than or equal to 32 hours, greater than or equal to 0.1 hour and less than or equal to 24 hours, greater than or equal to 0.1 hour and less than or equal to 18 hours, greater than or equal to 0.1 hour and less than or equal to 12 hours, greater than or equal to 0.1 hour and less than or equal to 6 hours, greater than or equal to 0.1 hour and less than or equal to 2 hours, greater than or equal to 0.5 hour and less than or equal to 32 hours, greater than or equal to 0.5 hour and less than or equal to 24 hours, greater than or equal to 0.5 hour and less than or equal to 18 hours, greater than or equal to 0.5 hour and less than or equal to 12 hours, greater than or equal to 0.5 hour and less than or equal to 6 hours, greater than or equal to 0.5 hour and less than or equal to 2 hours, greater than or equal to 1 hour and less than or equal to 32 hours, greater than or equal to 1 hour and less than or equal to 24 hours, greater than or equal to 1 hour and less than or equal to 18 hours, greater than or equal to 1 hour and less than or equal to 12 hours, greater than or equal to 1 hour and less than or equal to 6 hours, or even greater than or equal to 1 hour and less than or equal to 2 hours, or any and all sub-ranges formed from any of these endpoints.

[0216] In embodiments, at least one of the first ion exchange bath and the second ion exchange bath may comprise KNO.sub.3, NaNO.sub.3, or combinations thereof. In embodiments, at least one of the first ion exchange bath and the first ion exchange bath may comprise KNO.sub.3, NaNO.sub.3, Na.sub.2SO.sub.4, and K.sub.2SO.sub.4, or combinations thereof. While not wishing to be bound by theory, a mixed-bath including nitrates, sulfates, or other Na and/or K salts may be used at relatively high temperature (e.g., greater than 530? C.) because nitrates may decompose at these relatively high temperatures.

[0217] In embodiments, the relatively increased Young's Modulus and K.sub.Ic fracture toughness of the glass compositions described herein enables improved stress profiles (i.e., surface compressive stress, depth of layer, and maximum central tension) for the resultant glass articles, leading to improved mechanical performance.

[0218] In embodiments, a glass article made from the glass composition may have a surface compressive stress, after ion exchange strengthening, greater than or equal to 350 MPa. In embodiments, a glass article made from the glass composition may have a surface compressive stress, after ion exchange strengthening, greater than or equal to 350 MPa, greater than or equal to 400 MPa, greater than or equal to 450 MPa, greater than or equal to 500 MPa, or even greater than or equal to 550 MPa. In embodiments, a glass article made from the glass composition may have a surface compressive stress, after ion exchange strengthening, less than or equal to 900 MPa, less than or equal to 800 MPa, or even less than or equal to 700 MPa. In embodiments, a glass article made from the glass composition may have a surface compressive stress, after ion exchange strengthening, greater than or equal to 350 MPa and less than or equal to 900 MPa, greater than or equal to 350 MPa and less than or equal to 800 MPa, greater than or equal to 350 MPa and less than or equal to 700 MPa, greater than or equal to 400 MPa and less than or equal to 900 MPa, greater than or equal to 400 MPa and less than or equal to 800 MPa, greater than or equal to 400 MPa and less than or equal to 700 MPa, greater than or equal to 450 MPa and less than or equal to 900 MPa, greater than or equal to 450 MPa and less than or equal to 800 MPa, greater than or equal to 450 MPa and less than or equal to 700 MPa, greater than or equal to 500 MPa and less than or equal to 900 MPa, greater than or equal to 500 MPa and less than or equal to 800 MPa, greater than or equal to 500 MPa and less than or equal to 700 MPa, greater than or equal to 550 MPa and less than or equal to 900 MPa, greater than or equal to 550 MPa and less than or equal to 800 MPa, or even greater than or equal to 550 MPa and less than or equal to 700 MPa, or any and all sub-ranges formed from any of these endpoints.

[0219] In embodiments, a glass article made from the glass composition may have a depth of layer, after ion exchange strengthening, greater than or equal to 20 ?m. In embodiments, a glass article made from the glass composition may have a depth of layer, after ion exchange strengthening, greater than or equal to 20 ?m, greater than or equal to 25 ?m, or even greater than or equal to 30 ?m. In embodiments, a glass article made from the glass composition may have a depth of layer, after ion exchange strengthening, less than or equal to 300 ?m, less than or equal to 290 ?m, less than or equal to 280 ?m, or even less than or equal to 270 ?m. In embodiments, a glass article made from the glass composition may have a depth of layer, after ion exchange strengthening, greater than or equal to 20 ?m and less than or equal to 300 ?m, greater than or equal to 20 ?m and less than or equal to 290 ?m, greater than or equal to 20 ?m and less than or equal to 280 ?m, greater than or equal to 20 ?m and less than or equal to 270 ?m, greater than or equal to 25 ?m and less than or equal to 300 ?m, greater than or equal to 25 ?m and less than or equal to 290 ?m, greater than or equal to 25 ?m and less than or equal to 280 ?m, greater than or equal to 25 ?m and less than or equal to 270 ?m, greater than or equal to 30 ?m and less than or equal to 300 ?m, greater than or equal to 30 ?m and less than or equal to 290 ?m, greater than or equal to 30 ?m and less than or equal to 280 ?m, or even greater than or equal to 30 ?m and less than or equal to 270 ?m, or any and all sub-ranges formed from any of these endpoints.

[0220] In embodiments, a glass article made from the glass composition may have a depth of compression, after ion exchange strengthening, greater than or equal to 80 ?m. In embodiments, a glass article made from the glass composition may have a depth of compression, after ion exchange strengthening, greater than or equal to 45 ?m, greater than or equal to 50 ?m, or even greater than or equal to 55 ?m. In embodiments, a glass article made from the glass composition may have a depth of compression, after ion exchange strengthening, less than or equal to 140 ?m, less than or equal to 135 ?m, less than or equal to 130 ?m, or even less than or equal to 135 ?m. In embodiments, a glass article made from the glass composition may have a depth of compression, after ion exchange strengthening, greater than or equal to 45 ?m and less than or equal to 140 ?m, greater than or equal to 45 ?m and less than or equal to 135 ?m, greater than or equal to 45 ?m and less than or equal to 130 ?m, greater than or equal to 45 ?m and less than or equal to 125 ?m, greater than or equal to 50 ?m and less than or equal to 140 ?m, greater than or equal to 50 ?m and less than or equal to 135 ?m, greater than or equal to 50 ?m and less than or equal to 130 ?m, greater than or equal to 50 ?m and less than or equal to 125 ?m, greater than or equal to 55 ?m and less than or equal to 140 ?m, greater than or equal to 55 ?m and less than or equal to 135 ?m, greater than or equal to 55 ?m and less than or equal to 130 ?m, or even greater than or equal to 55 ?m and less than or equal to 125 ?m, or any and all sub-ranges formed from any of these endpoints.

[0221] In embodiments, a glass article made from the glass composition has a thickness t and may have a depth of compression, after ion exchange strengthening, greater than or equal to 0.05 t. In embodiments, a glass article made from the glass composition may have a depth of compression greater than or equal to 0.05 t or even greater than or equal to 0.1 t. In embodiments, a glass article made from the glass composition may have a depth of compression, after ion exchange strengthening, less than or equal to 0.3 t or even less than or equal to 0.25 t. In embodiments, a glass article made from the glass composition may have a depth of compression, after ion exchange strengthening, greater than or equal to 0.05 t and less than or equal to 0.3 t, greater than or equal to 0.05 t and less than or equal to 0.25 t, greater than or equal to 0.1 t and less than or equal to 0.3 t, or even greater than or equal to 0.1 t and less than or equal to 0.25 t, or any and all sub-ranges formed from any of these endpoints.

[0222] In embodiments, a glass article made from the glass composition may have a central tension, after ion exchange strengthening greater than or equal to 75 MPa, as measured at an article thickness of 0.6 mm. In embodiments, a glass article made from the glass composition may have a central tension, after ion exchange strengthening, greater than or equal to 30 MPa, greater than or equal to 35 MPa, greater than or equal to 40 MPa, greater than or equal to 45 MPa, or even greater than or equal to 50 MPa, as measured at an article thickness of 0.6 mm. In embodiments, a glass article made from the glass composition may have a central tension, after ion exchange strengthening, less than or equal to 250 MPa or even less than or equal to 225 MPa, as measured at an article thickness of 0.8 mm. In embodiments, a glass article made from the glass composition may have a central tension after ion exchange strengthening greater than or equal to 30 MPa and less than or equal to 250 MPa, greater than or equal to 30 MPa and less than or equal to 225 MPa, greater than or equal to 35 MPa and less than or equal to 250 MPa, greater than or equal to 35 MPa and less than or equal to 225 MPa, greater than or equal to 40 MPa and less than or equal to 250 MPa, greater than or equal to 40 MPa and less than or equal to 225 MPa, greater than or equal to 45 MPa and less than or equal to 250 MPa, greater than or equal to 45 MPa and less than or equal to 225 MPa, greater than or equal to 50 MPa and less than or equal to 250 MPa, or even greater than or equal to 50 MPa and less than or equal to 225 MPa, or any and all sub-ranges formed from any of these endpoints, as measured at an article thickness of 0.6 mm.

[0223] In embodiments, a glass article made from the glass composition may, after ion exchange strengthening, have a surface compressive stress greater than or equal to 350 MPa, a depth of layer greater than or equal to 20 ?m and less than or equal to 300 ?m, a depth of compression greater than or equal to 45 ?m and less than or equal to 140 ?m, and a central tension greater than or equal to 30 MPa and less than or equal to 250 MPa, as measured at an article thickness of 0.6 mm.

[0224] As described herein, the glass articles are ion exchanged at relatively high temperatures (i.e., greater than or equal to 500? C.) to offset the relatively slow rate of exchanging Na.sup.+ ions in the resultant glass article with K.sup.+ ions in a molten salt bath. However, while not wishing to be bound by theory, ion exchanging the glass article at relatively high temperature may result in stress relaxation, as evidenced by a knee region in the stress profile of the ion exchanged glass article. To prevent an undesirable amount of stress relaxation, the glass composition and resultant glass articles herein have a relatively high strain point (i.e., greater than or equal to 600? C.).

[0225] In embodiments, a glass article made from the glass composition may have a knee, after ion exchange strengthening, greater than or equal to 1 ?m and less than or equal to 30 ?m, as measured at an article thickness of about 0.5 mm to about 1 mm. In embodiments, a glass article made from the glass composition may have a knee, after ion exchange strengthening, greater than or equal to 1 ?m, greater than or equal to 3 ?m, or even greater than or equal to 7 ?m. In embodiments, a glass article made from the glass composition may have a knee, after ion exchange strengthening, less than or equal to 30 ?m or even less than or equal to 25 ?m. In embodiments, a glass article made from the glass composition may have a knee after ion exchange strengthening greater than or equal to 1 ?m and less than or equal to 30 ?m, greater than or equal to 1 ?m and less than or equal to 25 ?m, greater than or equal to 3 ?m and less than or equal to 30 ?m, greater than or equal to 3 ?m and less than or equal to 25 ?m, greater than or equal to 5 ?m and less than or equal to 30 ?m, or even greater than or equal to 5 ?m and less than or equal to 25 ?m, or any and all sub-ranges formed from any of these endpoints.

[0226] In embodiments, a glass article made from the glass composition may have a knee stress, after ion exchange strengthening greater than or equal to 50 MPa and less than or equal to 500 MPa, as measured at an article thickness of about 0.5 mm to about 1 mm. In embodiments, a glass article made from the glass composition may have a knee stress, after ion exchange strengthening, greater than or equal to 50 MPa, greater than or equal to 75 MPa, greater than or equal to 100 MPa, greater than or equal to 125 MPa, or even greater than or equal to 150 MPa. In embodiments, a glass article made from the glass composition may have a knee stress, after ion exchange strengthening, less than or equal to 500 MPa or even less than or equal to 400 MPa. In embodiments, a glass article made from the glass composition may have a knee stress after ion exchange strengthening greater than or equal to 50 MPa and less than or equal to 500 MPa, greater than or equal to 50 MPa and less than or equal to 400 MPa, greater than or equal to 75 MPa and less than or equal to 500 MPa, greater than or equal to 75 MPa and less than or equal to 400 MPa, greater than or equal to 100 MPa and less than or equal to 500 MPa, greater than or equal to 100 MPa and less than or equal to 400 MPa, greater than or equal to 125 MPa and less than or equal to 500 MPa, greater than or equal to 125 MPa and less than or equal to 400 MPa, greater than or equal to 150 MPa and less than or equal to 500 MPa, or even greater than or equal to 150 MPa and less than or equal to 400 MPa or any and all sub-ranges formed from any of these endpoints.

[0227] In embodiments, the glass compositions and resultant glass articles may have a knee, after ion exchange strengthening, greater than or equal to 1 ?m and less than or equal to 30 ?m and a knee stress, after ion exchange strengthening greater than or equal to 50 MPa and less than or equal to 500 MPa.

[0228] The glass compositions and resultant glass articles described herein may be used for a variety of applications including, for example, for cover glass or glass backplane applications in consumer or commercial electronic devices including, for example, LCD and LED displays, computer monitors, and automated teller machines (ATMs); for touch screen or touch sensor applications, for portable electronic devices including, for example, mobile telephones, personal media players, watches and tablet computers; for integrated circuit applications including, for example, semiconductor wafers; for photovoltaic applications; for architectural glass applications; for automotive or vehicular glass applications; or for commercial or household appliance applications. In embodiments, a consumer electronic device (i.e., smartphones, tablet computers, watches, personal computers, ultrabooks, televisions, and cameras), an architectural glass, and/or an automotive glass may comprise a glass article as described herein.

[0229] An exemplary electronic device incorporating any of the glass articles disclosed herein is shown in FIGS. 3 and 4. Specifically, FIGS. 3 and 4 show a consumer electronic device 200 including a housing 202 having front 204, back 206, and side surfaces 108; electrical components (not shown) that are at least partially inside or entirely within the housing and including at least a controller, a memory, and a display 210 at or adjacent to the front surface of the housing; and a cover substrate 212 at or over the front surface of the housing such that it is over the display. In embodiments, at least a portion of at least one of the cover substrate 212 and the housing 202 may include any of the glass articles disclosed herein.

EXAMPLES

[0230] In order that various embodiments be more readily understood, reference is made to the following examples, which are intended to illustrate various embodiments of the glass compositions described herein.

[0231] Table 1 shows example glass compositions and a comparative glass composition (in terms of mol %) and the respective properties of the glass compositions. Glass articles were formed having the examples glass compositions E1-E80 and comparative glass compositions C1 and C2.

TABLE-US-00001 TABLE 1 Example E1 E2 E3 E4 E5 E6 E7 SiO.sub.2 64.15 64.11 63.61 63.97 63.29 63.91 62.05 Al.sub.2O.sub.3 17.92 18.00 17.91 17.92 17.94 17.91 19.03 P.sub.2O.sub.5 0.99 1.97 0.98 1.97 0.97 1.97 0.99 Na.sub.2O 11.26 11.27 11.48 11.36 11.59 11.26 11.73 MgO 5.49 4.48 2.91 2.29 0.12 0.10 6.05 CaO 0.04 0.03 2.95 2.34 5.94 4.70 0.04 Y.sub.2O.sub.3 ZrO.sub.2 SnO.sub.2 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Sum 100 100 100 100 100 100 100 RO 5.53 4.51 5.86 4.63 6.06 4.80 6.09 (Na.sub.2O + RO)/Al.sub.2O.sub.3 0.94 0.88 0.97 0.89 0.98 0.90 0.94 Density (g/cm.sup.3) 2.452 2.435 2.461 2.442 2.468 2.449 2.465 CTE (?10.sup.?7/? C.) Strain Point (? C.) 706 707 706 709 724 724 703 Anneal Point (? C.) 755 760 755 762 772 777 751 Softening Point (? C.) 825 Poisson's Ratio 0.214 0.210 0.216 0.212 0.214 0.209 0.213 Shear Modulus (GPa) 32.1 31.4 31.9 31.2 31.6 31.0 31.9 Young's Modulus (GPa) 78.0 76.0 77.6 75.7 76.7 74.8 77.2 SOC (nm/mm/MPa) 2.977 3.051 2.96 3.024 2.94 3.022 2.942 Refractive Index 1.5078 1.5037 1.5101 1.5058 1.5128 1.5072 1.5102 Zircon Breakdown (? C.) 1235 1245 1180 1215 1150 1190 1220 VFT A ?6.391 ?3.740 ?3.558 ?3.599 ?3.598 ?3.463 ?3.010 VFT B 15077 8821 8523 8561 8651 8281 6929 VFT To ?111.6 216.1 225.1 238.3 204.2 262.8 322.0 Liquidus Temp. (? C.) 1360 1360 1330 1330 >1330 1290 1395 Liquidus Viscosity (P) 7144 9354 14325 17487 39729 2801 Example E8 E9 E10 E11 E12 E13 E14 SiO.sub.2 62.15 61.71 62.17 61.64 62.02 63.11 63.55 Al.sub.2O.sub.3 18.96 19.09 19.01 19.39 19.09 18.03 18.19 P.sub.2O.sub.5 1.99 0.98 1.99 0.99 0.49 0.25 Na.sub.2O 11.73 12.96 12.70 13.78 13.72 11.52 11.28 MgO 5.02 5.11 3.98 5.03 4.04 6.65 6.53 CaO 0.04 0.04 0.03 0.04 0.03 0.05 0.05 Y.sub.2O.sub.3 ZrO.sub.2 SnO.sub.2 0.01 0.01 0.01 0.01 0.01 0.11 0.11 Sum 100 100 100 100 100 100 100 RO 5.06 5.15 4.01 5.07 4.07 6.70 6.58 (Na.sub.2O + RO)/Al.sub.2O.sub.3 0.89 0.95 0.88 0.97 0.93 1.01 0.98 Density (g/cm.sup.3) 2.447 2.457 2.443 2.471 2.457 2.459 2.463 CTE (?10.sup.?7/? C.) Strain Point (? C.) 704 704 702 700 702 704 706 Anneal Point (? C.) 755 754 753 750 754 751 756 Softening Point (? C.) 832 831 830 827 831 Poisson's Ratio 0.213 0.220 0.208 0.216 0.210 0.224 0.223 Shear Modulus (GPa) 31.6 32.3 31.0 32.1 31.4 32.4 32.6 Young's Modulus (GPa) 76.8 78.8 74.9 78.2 75.8 79.3 79.9 SOC (nm/mm/MPa) 2.994 2.966 3.008 2.909 2.984 2.927 2.923 Refractive Index 1.5060 1.5090 1.5044 1.5121 1.5075 1.509 1.5115 Zircon Breakdown (? C.) 1190 1100 1230 1110 1115 VFT A ?3.406 ?3.409 ?3.557 ?3.085 ?3.260 ?3.169 ?3.177 VFT B 7886 7833 8267 7025 7643 7374 7386 VFT To 264.0 267.8 248.5 312.3 285.5 294.3 292.8 Liquidus Temp. (? C.) 1400 1355 1355 1405 1320 1355 1355 Liquidus Viscosity (P) 3433 6252 8209 2210 13416 6073 5977 Example E15 E16 E17 E18 E19 E20 E21 SiO.sub.2 63.15 63.65 63.13 63.55 57.62 59.70 60.90 Al.sub.2O.sub.3 18.09 18.22 18.05 18.10 19.34 18.99 19.03 P.sub.2O.sub.5 0.49 0.25 0.49 0.25 0.23 0.47 Na.sub.2O 11.59 11.26 11.58 11.29 13.58 15.14 14.50 MgO 3.25 3.22 0.13 0.13 9.25 5.73 4.91 CaO 3.30 3.24 6.45 6.53 0.05 0.04 Y.sub.2O.sub.3 ZrO.sub.2 SnO.sub.2 0.11 0.11 0.11 0.11 Sum 100 100 100 100 100 100 100 RO 6.53 6.46 6.58 6.66 9.25 5.78 4.95 (Na.sub.2O + RO)/Al.sub.2O.sub.3 1.00 0.97 1.01 0.99 1.10 1.02 Density (g/cm.sup.3) 2.467 2.475 2.478 2.483 2.485 2.469 2.467 CTE (?10.sup.?7/? C.) Strain Point (? C.) 703 707 723 728 685 699 Anneal Point (? C.) 753 755 773 778 733 750 Softening Point (? C.) 973 988 Poisson's Ratio 0.220 0.221 0.219 0.219 0.219 0.219 Shear Modulus (GPa) 32.2 32.4 32.3 31.9 31.6 31.5 Young's Modulus (GPa) 78.6 79.2 78.9 77.8 76.9 76.7 SOC (nm/mm/MPa) 2.92 2.912 2.889 2.906 2.918 2.952 Refractive Index 1.512 1.5128 1.5142 1.5173 1.5120 1.5123 Zircon Breakdown (? C.) 1060 1105 VFT A ?3.410 ?3.064 ?3.420 ?3.138 ?3.491 ?3.535 VFT B 8034 7217 7927 7449 8110 8176 VFT To 258.2 320.4 262.4 309.4 243.4 240.8 Liquidus Temp. (? C.) 1295 1300 1315 1305 1375 1340 Liquidus Viscosity (P) 21824 20081 12914 22081 4736 7996 Example E22 E23 E24 E25 E26 E27 E28 SiO.sub.2 60.16 60.38 58.49 59.34 62.89 62.84 61.36 Al.sub.2O.sub.3 19.05 19.04 20.07 20.01 17.95 18.03 17.89 P.sub.2O.sub.5 0.24 0.48 0.24 0.48 0.49 0.49 0.48 Na.sub.2O 15.13 14.83 15.33 14.89 11.46 11.25 11.71 MgO 5.24 5.07 5.67 5.10 0.13 0.14 0.16 CaO 0.04 0.04 0.05 0.04 6.93 7.10 8.26 Y.sub.2O.sub.3 ZrO.sub.2 SnO.sub.2 0.11 0.11 0.11 Sum 100 100 100 100 100 100 100 RO 5.28 5.11 5.72 5.14 7.06 7.24 8.42 (Na.sub.2O + RO)/Al.sub.2O.sub.3 1.07 1.05 1.05 1.00 1.03 1.03 1.12 Density (g/cm.sup.3) 2.474 2.469 2.481 2.477 2.481 2.487 2.494 CTE (?10.sup.?7/? C.) Strain Point (? C.) 688 693 695 696 Anneal Point (? C.) 736 741 744 745 Softening Point (? C.) 976 982 973 979 Poisson's Ratio 0.219 0.216 0.221 0.220 0.216 0.214 0.219 Shear Modulus (GPa) 31.6 31.6 31.8 31.7 31.9 32.1 32.1 Young's Modulus (GPa) 77.0 76.9 77.6 77.4 77.6 77.8 78.3 SOC (nm/mm/MPa) 2.904 2.926 2.910 2.888 2.915 2.896 2.851 Refractive Index 1.5098 1.5108 1.5087 1.5097 1.5152 1.5161 1.5181 Zircon Breakdown (? C.) 1055 1075 1125 1040 VFT A ?3.059 ?3.506 ?2.751 ?3.083 ?3.153 ?3.258 ?3.169 VFT B 7159 8072 6368 7035 7490 7506 7532 VFT To 292.2 243.5 356.6 315.0 294.4 295.6 271.8 Liquidus Temp. (? C.) 1345 1345 >1400 1380 1330 1310 1315 Liquidus Viscosity (P) 5511 6636 3330 12009 13844 11251 Example E29 E30 E31 E32 E33 E34 E35 SiO.sub.2 61.33 62.30 61.63 60.19 59.91 59.67 59.84 Al.sub.2O.sub.3 17.97 18.02 18.05 19.10 19.07 19.05 18.98 P.sub.2O.sub.5 0.49 0.49 0.49 0.24 0.49 0.24 0.48 Na.sub.2O 11.47 11.46 11.39 12.69 12.72 12.91 12.89 MgO 0.16 1.05 2.04 7.57 7.61 3.98 3.83 CaO 8.42 6.53 6.25 0.06 0.06 3.98 3.83 Y.sub.2O.sub.3 ZrO.sub.2 SnO.sub.2 0.11 0.11 0.11 RO 8.58 7.58 8.29 7.63 7.67 7.96 7.66 Sum 100 100 100 100 100 100 100 (Na.sub.2O + RO)/Al.sub.2O.sub.3 1.12 1.06 1.09 1.06 1.07 1.10 1.08 Density (g/cm.sup.3) 2.5 2.484 2.494 2.483 2.48 2.495 2.493 CTE (?10.sup.?7/? C.) Strain Point (? C.) 695 692 690 683 Anneal Point (? C.) 742 740 738 733 Softening Point (? C.) 963 966 961 962 Poisson's ratio 0.218 0.219 0.217 0.225 0.224 0.222 0.228 Shear Modulus (GPa) 32.1 32.1 32.3 32.6 32.5 32.5 32.4 Young's Modulus (GPa) 78.2 78.2 78.8 79.8 79.4 79.4 79.5 SOC (nm/mm/MPa) 2.854 2.896 2.862 2.884 2.898 2.851 2.863 Refractive Index 1.5196 1.5157 1.5184 1.5142 1.5140 1.5177 1.5186 Zircon Breakdown (? C.) VFT A ?2.679 ?3.233 ?3.125 ?3.002 ?2.631 ?2.926 ?3.242 VFT B 6358 7509 7178 6718 6092 6612 7286 VFT To 350.6 291.1 299.6 317.5 359.4 331.0 279.0 Liquidus Temp. (? C.) 1315 1300 1270 1230 1275 Liquidus Viscosity (P) 8202 16220 18696 26843 11827 Fracture Toughness (MPa .Math. m.sup.1/2) 0.8 Example E36 E37 E38 E39 E40 E41 E42 SiO.sub.2 59.71 57.77 60.30 59.61 60.56 59.59 60.52 Al.sub.2O.sub.3 18.93 18.77 18.45 18.87 18.39 18.89 18.37 P.sub.2O.sub.5 0.24 0.47 0.48 0.48 0.49 0.49 0.48 Na.sub.2O 12.84 13.15 11.82 11.78 11.77 11.77 11.84 MgO 0.16 0.19 0.09 0.09 2.60 3.05 2.06 CaO 7.94 9.48 8.72 9.01 6.04 6.07 6.57 Y.sub.2O.sub.3 ZrO.sub.2 SnO.sub.2 0.01 Sum 100 100 100 100 100 100 100 RO 7.10 9.67 8.81 9.10 8.64 9.12 8.63 (Na.sub.2O + RO)/Al.sub.2O.sub.3 1.11 1.22 1.12 1.11 1.11 1.11 1.11 Density (g/cm.sup.3) 2.506 2.502 2.507 2.515 2.500 2.505 2.501 CTE (?10.sup.?7/? C.) 68.4 69.4 66.4 66.1 67.3 Strain Point (? C.) 697 706 711 707 697 691 696 Anneal Point (? C.) 744 755 758 752 745 737 744 Softening Point (?) 972 978 Poisson's Ratio 0.225 0.220 0.223 0.226 0.224 0.226 0.225 Shear Modulus (GPa) 32.0 31.9 32.1 32.3 32.4 32.6 32.4 Young's Modulus (GPa) 78.5 77.8 78.6 79.1 79.3 80.0 79.4 SOC (nm/mm/MPa) 2.837 2.841 2.847 2.829 2.853 2.839 2.852 Refractive Index 1.5181 1.5192 1.5215 1.5231 1.5193 1.5213 1.5198 Zircon Breakdown (? C.) VFT A ?3.058 ?3.163 ?3.160 ?3.027 ?3.191 ?3.258 ?3.347 VFT B 6918 7249 7236 6903 7255 7308 7571 VFT To 311.1 291.4 286.6 295.4 284.6 277.4 264.4 Liquidus Temp. (? C.) 1370 1300 1300 1260 1230 1255 1240 Liquidus Viscosity (P) 2985 10563 9557 13469 30431 16514 25915 Example E43 E44 E45 E46 E47 E48 E49 SiO.sub.2 59.59 59.30 59.18 59.14 59.44 58.97 58.98 Al.sub.2O.sub.3 18.85 18.89 18.85 18.72 18.84 18.90 18.61 P.sub.2O.sub.5 0.49 0.24 0.24 0.24 0.24 0.24 0.24 Na.sub.2O 11.86 13.32 13.34 13.16 13.39 13.44 13.31 MgO 2.06 3.97 3.91 3.79 3.91 3.93 3.99 CaO 7.00 3.88 3.82 3.78 3.79 3.89 3.80 Y.sub.2O.sub.3 0.25 0.50 1.02 ZrO.sub.2 0.23 0.46 0.91 SnO.sub.2 0.01 0.01 Sum 100 100 100 100 100 100 100 RO 9.06 7.85 7.73 7.57 7.70 7.82 7.79 (Na.sub.2O + RO)/Al.sub.2O.sub.3 1.11 1.12 1.12 1.11 1.12 1.12 1.13 Density (g/cm.sup.3) 2.510 2.508 2.523 2.550 2.505 2.510 2.524 CTE (?10.sup.?7/? C.) 67.5 70.3 70.0 69.8 71.1 69.9 69.3 Strain Point (? C.) 695 Anneal Point (? C.) 741 Softening Point (? C.) Poisson's ratio 0.226 0.224 0.225 0.227 0.225 0.225 0.223 Shear Modulus (GPa) 32.6 32.5 32.5 32.9 32.4 32.5 32.8 Young's Modulus (GPa) 79.8 79.4 79.8 80.6 79.4 79.6 80.2 SOC (nm/mm/MPa) 2.816 2.849 2.829 2.808 2.864 2.865 2.874 Refractive Index 1.522 1.5200 1.5217 1.5252 Zircon Breakdown (? C.) VFT A ?2.919 ?3.231 ?3.161 ?3.021 ?2.860 ?2.819 ?3.170 VFT B 6509 7220 6994 6586 6573 6461 6991 VFT To 344.8 280.1 296.4 324.4 322.1 328.6 298.3 Liquidus Temp. (? C.) 1260 1280 1255 1230 1275 1310 >1330 Liquidus Viscosity (P) 15599 9766 13631 17845 10914 5818 Example E50 E51 E52 E53 E54 E55 E56 SiO.sub.2 58.44 58.56 58.44 58.62 58.48 58.77 58.59 Al.sub.2O.sub.3 19.33 19.42 19.45 19.45 19.43 19.33 19.60 P.sub.2O.sub.5 0.49 0.49 0.49 0.49 0.49 0.49 0.24 Na.sub.2O 11.70 11.75 11.77 11.70 11.80 11.73 12.98 MgO 0.18 1.88 3.86 5.73 7.72 9.47 5.04 CaO 9.69 7.74 5.83 3.85 1.95 0.07 3.36 Y.sub.2O.sub.3 ZrO.sub.2 SnO.sub.2 0.11 0.11 0.11 0.11 0.11 0.11 Sum 100 100 100 100 100 100 100 RO 9.87 9.62 9.69 9.58 9.67 9.45 8.40 (Na.sub.2O + RO)/Al.sub.2O.sub.3 1.12 1.10 1.10 1.09 1.10 1.10 1.09 Density (g/cm.sup.3) 2.524 2.518 2.513 2.507 2.500 2.496 2.502 CTE (?10.sup.?7/? C.) 69.1 67.2 65.6 63.9 62.3 61.0 66.3 Strain Point (? C.) 708 699 699 691 689 694 687 Anneal Point (? C.) 753 745 735 737 734 740 733 Softening Point (? C.) 963 Poisson's Ratio 0.226 0.229 0.228 0.228 0.229 0.227 0.228 Shear Modulus (GPa) 32.6 32.8 33.0 33.1 33.2 33.3 32.8 Young's Modulus (GPa) 79.9 80.4 80.9 81.3 81.8 81.8 80.5 SOC (nm/mm/MPa) 2.78 2.799 2.815 2.819 2.801 2.843 2.845 Refractive Index 1.5258 1.5235 1.5228 1.5210 1.5200 1.5180 1.5189 Zircon Breakdown (? C.) VFT A ?2.659 ?2.841 ?2.943 ?3.367 ?2.872 ?3.057 VFT B 5891 6317 6529 7340 6333 6964 VFT To 373.3 349.7 328.4 274.3 341.6 304.2 Liquidus Temp. (? C.) 1305 1310 1270 1350 >1420 1270 Liquidus Viscosity (P) 4614 5457 9786 2859 14250 Example E57 E58 E59 E60 E61 E62 E63 SiO.sub.2 59.02 58.93 58.09 57.72 57.87 55.82 55.33 Al.sub.2O.sub.3 19.57 19.53 20.03 19.97 20.08 19.90 19.63 P.sub.2O.sub.5 0.24 0.24 0.24 0.24 0.24 0.23 0.23 Na.sub.2O 12.78 12.79 12.71 13.00 12.91 12.26 12.48 MgO 4.09 3.31 5.20 4.39 3.47 0.22 2.43 CaO 4.14 5.04 3.56 4.53 5.26 11.41 9.75 Y.sub.2O.sub.3 ZrO.sub.2 SnO.sub.2 0.10 0.10 Sum 100 100 100 100 100 100 100 RO 8.23 8.35 8.76 8.92 8.73 11.63 12.18 (Na.sub.2O + RO)/Al.sub.2O.sub.3 1.07 1.08 1.07 1.10 1.08 1.20 1.26 Density (g/cm.sup.3) 2.503 2.506 2.507 2.504 2.514 CTE (?10.sup.?7/? C.) 67.3 66.5 66.3 67.7 68.8 Strain Point (? C.) 690 679 692 696 690 699 676 Anneal Point (? C.) 738 726 738 743 737 745 721 Softening Point (? C.) 960 944 950 959 950 Poisson's Ratio 0.228 0.226 0.226 0.229 0.227 0.228 0.230 Shear Modulus (GPa) 32.7 32.6 33.0 33.0 33.2 33.0 33.1 Young's Modulus (GPa) 80.3 80.0 81.1 80.9 81.4 81.0 81.4 SOC (nm/mm/MPa) 2.833 2.823 2.819 2.800 2.801 2.754 2.736 Refractive Index 1.5201 1.5209 1.5213 1.5218 1.5231 1.5285 1.5271 Zircon Breakdown (? C.) VFT A ?3.297 ?3.297 ?3.097 ?2.929 ?3.282 ?2.883 ?2.933 VFT B 7320 7320 6928 6608 7178 6227 6347 VFT To 281.6 281.6 302.7 330.0 290.0 354.7 347.9 Liquidus Temp. (? C.) 1325 1260 1360 1335 1290 1290 1280 Liquidus Viscosity (P) 5228 15290 2856 4428 7863 5959 7517 Example E64 E65 E66 E67 E68 E69 E70 SiO.sub.2 58.90 57.27 56.93 56.03 56.39 56.38 55.47 Al.sub.2O.sub.3 20.08 20.07 20.33 20.16 20.59 20.46 20.55 P.sub.2O.sub.5 0.24 0.24 0.24 0.24 0.49 0.48 0.48 Na.sub.2O 11.37 11.96 11.70 11.83 11.82 11.86 12.46 MgO 3.66 6.12 8.59 11.52 2.55 5.18 2.65 CaO 5.59 4.19 2.06 0.08 8.00 5.48 8.24 Y.sub.2O.sub.3 ZrO.sub.2 SnO.sub.2 0.11 0.10 0.10 0.10 0.11 0.11 0.11 Sum 100 100 100 100 100 100 100 RO 9.25 10.31 10.65 11.60 10.55 10.66 10.89 (Na.sub.2O + RO)/Al.sub.2O.sub.3 1.03 1.11 1.10 1.16 1.09 1.10 1.14 Density (g/cm.sup.3) 2.532 2.527 2.545 CTE (?10.sup.?7/? C.) 67.1 63.7 70.7 Strain Point (? C.) 693 677 689 682 682 689 Anneal Point (? C.) 738 723 734 724 726 735 Softening Point (? C.) 921 938 934 Poisson's Ratio 0.229 0.229 0.234 0.230 0.229 0.229 0.229 Shear Modulus (GPa) 33.3 33.2 34.1 33.7 33.3 33.8 33.3 Young's Modulus (GPa) 81.9 81.6 84.3 83.0 81.9 83.1 81.8 SOC (nm/mm/MPa) 2.785 2.790 2.801 2.817 2.718 2.731 2.703 Refractive Index 1.5249 1.5239 1.5224 1.5203 1.5279 1.5264 1.5286 Zircon Breakdown (? C.) VFT A ?2.737 ?2.923 ?3.154 ?2.721 ?2.806 ?2.776 ?3.223 VFT B 6011 6287 6695 5866 6210 6118 6950 VFT To 362.8 342.1 316.9 372.5 365.0 364.6 310.0 Liquidus Temp. (? C.) 1240 1400 >1420 >1410 >1305 >1335 1280 Liquidus Viscosity (P) 13039 1046 8743 Example E71 E72 E73 E74 E75 E76 E77 SiO.sub.2 55.57 55.22 54.63 59.47 58.63 57.30 58.23 Al.sub.2O.sub.3 20.54 20.90 21.08 18.42 18.31 18.05 19.26 P.sub.2O.sub.5 0.48 0.47 0.48 0.25 0.25 0.25 0.49 Na.sub.2O 12.49 12.22 12.44 12.44 12.31 12.04 11.04 MgO 5.24 2.69 5.56 3.59 3.63 3.62 3.64 CaO 5.53 8.33 5.64 3.69 3.73 3.68 5.68 Y.sub.2O.sub.3 2.01 3.01 4.92 1.52 ZrO.sub.2 SnO.sub.2 0.11 0.11 0.11 0.10 0.10 0.10 0.10 Sum 100 100 100 100 100 100 100 RO 10.77 11.02 11.20 7.28 7.36 7.30 9.32 (Na.sub.2O + RO)/Al.sub.2O.sub.3 1.13 1.11 1.12 1.07 1.07 1.07 1.06 Density (g/cm.sup.3) 2.531 2.542 2.538 2.602 2.655 2.76 2.592 CTE (?10.sup.?7/? C.) 67.2 67.3 68.6 63.5 Strain Point (? C.) 685 687 671 697 Anneal Point (? C.) 730 732 718 744 Softening Point (? C.) 942 946 924 Poisson's Ratio) 0.233 0.228 0.231 0.223 0.232 0.232 0.229 Shear Modulus (GPa) 33.9 33.4 33.6 33.7 34.3 35.2 34.1 Young's Modulus (GPa) 83.6 82.1 82.9 82.4 84.4 86.7 83.8 SOC (nm/mm/MPa) 2.732 2.729 2.753 2.768 2.739 2.627 2.763 Refractive Index 1.5266 1.5294 1.5272 1.5334 1.5414 1.5570 1.5346 Zircon Breakdown (? C.) VFT A ?1.323 ?2.859 ?3.199 ?2.679 ?2.091 ?2.861 ?2.556 VFT B 3341 6158 6857 5721 4371 5910 5004 VFT To 651.3 351.5 293.5 376.7 506.1 379.8 452.5 Liquidus Temp. l (? C.) ~1370 1285 >1320 1215 1310 1415 1190 Liquidus Viscosity (P) 5462 13981 2216 705 16968 Fracture Toughness (MPa .Math. m.sup.1/2) 0.81 Example E78 E79 E80 SiO.sub.2 58.02 57.52 60.1 Al.sub.2O.sub.3 18.51 19.68 19.2 P.sub.2O.sub.5 0.49 0.25 Na.sub.2O 10.85 12.46 12.8 MgO 3.46 3.33 3.9 CaO 5.51 5.10 3.9 Y.sub.2O.sub.3 3.02 1.52 ZrO.sub.2 SnO.sub.2 0.10 0.11 0.1 Sum 100 100 100 RO 8.97 8.43 7.8 (Na.sub.2O + RO)/Al.sub.2O.sub.3 1.07 1.06 0.26 Density (g/cm.sup.3) 2.674 2.592 2.503 CTE (?10.sup.?7/? C.) 63.8 67.6 Strain Point (? C.) 704 694 682 Anneal Point (? C.) 748 740 729 Softening Point (? C.) 955 Poisson's Ratio 0.228 0.227 0.224 Shear Modulus (GPa) 34.9 33.9 32.7 Young's Modulus (GPa) 85.6 83.2 80.1 SOC (nm/mm/MPa) 2.683 2.756 2.802 Refractive Index 1.5461 1.5337 1.519 Zircon Breakdown (? C.) VFT A ?2.882 ?2.882 ?3.218 VFT B 5942 5942 7349 VFT To 374.8 374.8 275.1 Liquidus Temp. (? C.) 1275 1270 1290 Liquidus Viscosity (P) 5236 5700 10537 Fracture Toughness (MPa .Math. m.sup.1/2) 0.81 Example C1 C2 SiO.sub.2 66.37 67.37 B.sub.2O.sub.3 0.60 3.73 Al.sub.2O.sub.3 10.29 12.65 Na.sub.2O 13.80 13.72 K.sub.2O 2.40 0.01 MgO 5.74 2.36 CaO 0.59 0.04 SnO.sub.2 0.21 0.10 Fe.sub.2O.sub.3 0.01 Sum 100.00 100.00 RO 6.33 2.40 (Na.sub.2O + RO)/Al.sub.2O.sub.3 1.96 1.27 Young's Modulus (GPa) 72.9 69.3 Strain Point (? C.) 553 572 Fracture Toughness (MPa .Math. m.sup.1/2) 0.73 0.66

[0232] As indicated by the example glass compositions in Table 1, glass compositions and the resultant glass articles as described herein have increased Young's Modulus and fracture toughness such that the glass compositions and the resultant glass articles are more resistant to damage.

[0233] Referring now to FIG. 6, example glass composition E42 having a thickness of 0.6 mm was first ion exchanged in a 18.2% NaNO.sub.3/54.9% KNO.sub.3/6.6% Na.sub.2SO.sub.4/20.3% K.sub.2SO.sub.4 molten salt bath at 600? C. for 16 hours and then ion exchanged in a 100% KNO.sub.3 molten salt bath at 370? C. for 1 hour. As shown by the grey region in FIG. 6, the stress profile had a knee region, indicated by the flat, greater-than-200 MPa compressive stress for up to 8% of the thickness of the glass. While not wishing to be bound by theory, it is believed that the knee region is the result of ion exchanging the glass article and a relatively high temperature. It is also believed that the relatively high strain point of example glass composition E42 (i.e., 696? C.) prevented the glass article from relaxing an undesirable amount during ion exchange.

[0234] Table 2 shows the CS, DOL, and CT of example ion exchanged glass articles EA1-EA36 formed by ion exchanging glass articles having a thickness of 0.6 mm and made from example glass compositions, as indicated in Table 2, at a temperature of 530? C. for 4, 9, and 16 hours. The ion exchange solution was a 88.5% KNO.sub.3/11.5% K.sub.2SO.sub.4 molten salt bath.

TABLE-US-00002 TABLE 2 Example EA1 EA2 EA3 EA4 EA5 Composition E26 E27 E28 E30 E31 16 hours CS (MPa) 653 644 652 665 685 DOL (?m) 113 106 100 106 94 CT (MPa) 148 137 124 145 111 Example EA6 EA7 EA8 EA9 EA10 Composition E32 E33 E35 E36 E37 4 hours CS (MPa) 831 816 856 828 DOL (?m) 56 56 54 57 CT (MPa) 83 73 80 67 9 hours CS (MPa) 766 751 773 783 DOL (?m) 83 87 82 80 CT (MPa) 118 128 124 120 16 hours CS (MPa) 706 720 689 716 DOL (?m) 107 109 111 112 CT (MPa) 138 157 129 143 Example EA11 EA12 EA13 EA14 EA15 Composition E38 E39 E40 E41 E42 4 hours CS (MPa) 803 851 832 859 DOL (?m) 44 44 42 41 CT (MPa) 52 58 58 55 9 hours CS (MPa) 756 780 792 801 778 DOL (?m) 67 60 68 59 64 CT (MPa) 73 74 81 73 86 16 hours CS (MPa) 701 725 738 750 725 DOL (?m) 92 83 85 79 89 CT (MPa) 110 97 96 97 113 Example EA16 EA17 EA18 EA19 EA20 Composition E43 E44 E45 E46 E50 4 hours CS (MPa) 863 810 DOL (?m) 39 38 CT (MPa) 57 49 9 hours CS (MPa) 799 765 DOL (?m) 61 58 CT (MPa) 82 77 16 hours CS (MPa) 749 781 789 802 712 DOL (?m) 82 106 107 98 75 CT (MPa) 109 135 141 138 99 Example EA21 EA22 EA23 EA24 EA25 Composition E51 E52 E53 E54 E56 4 hours CS (MPa) 827 848 837 831 887 DOL (?m) 29 37 38 36 48 CT (MPa) 44 56 53 42 69 9 hours CS (MPa) 789 788 790 769 812 DOL (?m) 55 56 56 51 73 CT (MPa) 66 73 79 74 104 16 hours CS (MPa) 737 727 736 733 750 DOL (?m) 74 75 74 52 98 CT (MPa) 96 107 94 125 Example EA26 EA27 EA28 EA29 EA30 Composition E57 E58 E59 E60 E61 4 hours CS (MPa) 879 894 885 886 905 DOL (?m) 39 49 44 38 44 CT (MPa) 60 76 73 59 68 9 hours CS (MPa) 820 802 811 831 DOL (?m) 73 75 69 67 CT (MPa) 113 128 115 97 16 hours CS (MPa) 755 738 752 781 783 DOL (?m) 96 90 87 87 88 CT (MPa) 138 136 131 119 104 Example EA31 EA32 EA33 EA34 EA35 EA36 Composition E74 E75 E76 E77 E78 E79 16 hours CS (MPa) 830 849 787 804 810 845 DOL (?m) 79 73 102 50 41 69 CT (MPa) 108 93 128 62 72 88

[0235] As indicated by the example ion exchanged glass articles in Table 2, glass articles formed from the glass compositions having increased Young's Modulus and K.sub.Ic fracture toughness as described herein may be ion exchanged in one step to achieve desired stress profiles.

[0236] Table 3 shows the CS, DOL, and CT of example ion exchanged glass articles EA37-EA75 formed by ion exchanging glass articles having a thickness of 0.6 mm and made from example glass compositions, as indicated in Table 3, at a temperature of 600? C. for 4, 9, and 16 hours. The ion exchange solution was a 88.5% KNO.sub.3/11.5% K.sub.2SO.sub.4 molten salt bath.

TABLE-US-00003 TABLE 3 Example EA37 EA38 EA39 EA40 EA41 Composition E3 E4 E32 E33 E34 4 hours CS (MPa) 479 581 521 543 DOL (?m) 127 105 110 102 CT (MPa) 109 119 145 116 9 hours CS (MPa) 481 454 379 DOL (?m) 162 176 172 CT (MPa) 170 182 16 hours CS (MPa) 336 247 376 377 359 DOL (?m) 228 262 207 211 206 CT (MPa) 239 249 211 194 212 Example EA42 EA43 EA44 EA45 EA46 Composition E35 E36 E37 E38 E39 4 hours CS (MPa) 551 547 523 539 525 DOL (?m) 108 109 112 88 84 CT (MPa) 122 116 119 84 74 9 hours CS (MPa) 423 521 442 439 DOL (?m) 160 165 135 124 CT (MPa) 177 161 133 112 16 hours CS (MPa) 376 363 491 DOL (?m) 210 171 164 CT (MPa) 220 196 196 170 155 Example EA47 EA48 EA49 EA50 EA51 Composition E40 E41 E42 E43 E44 4 hours CS (MPa) 530 547 530 572 DOL (?m) 94 83 91 84 CT (MPa) 88 85 86 83 9 hours CS (MPa) 460 551 518 464 DOL (?m) 139 129 135 120 CT (MPa) 125 122 135 116 16 hours CS (MPa) 391 515 376 428 411 DOL (?m) 175 152 164 157 217 CT (MPa) 165 141 166 153 221 Example EA52 EA53 EA54 EA55 EA56 Composition E45 E46 E50 E51 E52 4 hours CS (MPa) 523 645 549 DOL (?m) 75 84 80 CT (MPa) 85 93 79 9 hours CS (MPa) 489 509 528 DOL (?m) 110 111 111 CT (MPa) 137 131 108 16 hours CS (MPa) 399 387 410 412 DOL (?m) 203 188 148 140 CT (MPa) 218 208 174 155 Example EA57 EA58 EA59 EA60 EA61 Composition E53 E54 E56 E57 E58 4 hours CS (MPa) 558 530 534 607 DOL (?m) 78 71 100 102 81 CT (MPa) 81 57 114 129 120 9 hours CS (MPa) 449 455 498 516 490 DOL (?m) 111 114 138 137 142 CT (MPa) 124 98 158 175 185 16 hours CS (MPa) 409 451 396 423 424 DOL (?m) 142 148 179 194 188 CT (MPa) 175 150 212 226 234 Example EA62 EA63 EA64 EA65 EA66 Composition E59 E60 E61 E62 E63 4 hours CS (MPa) 604 554 611 DOL (?m) 95 84 92 CT (MPa) 131 113 120 9 hours CS (MPa) 490 519 499 DOL (?m) 129 129 127 CT (MPa) 168 144 147 16 hours CS (MPa) 430 388 469 448 480 DOL (?m) 169 154 166 126 127 CT (MPa) 211 207 188 148 148 Example EA67 EA68 EA69 EA70 EA71 Composition E64 E70 E72 E74 E75 4 hours CS (MPa) 576 553 724 652 DOL (?m) 71 67 79 75 CT (MPa) 87 83 95 81 9 hours CS (MPa) 454 DOL (?m) 88 CT (MPa) 105 135 95 16 hours CS (MPa) 511 482 DOL (?m) 128 129 CT (MPa) 131 142 160 138 Example EA72 EA73 EA74 EA75 Composition E76 E77 E78 E79 4 hours CS (MPa) 598 674 642 DOL (?m) 56 45 69 CT (MPa) 91 59 46 80 9 hours CT (MPa) 125 82 101 112 16 hours CT (MPa) 169 107 136 133

[0237] As indicated by the example ion exchanged glass articles in Table 3, glass articles formed from the glass compositions having increased Young's Modulus and K.sub.Ic fracture toughness as described herein may be ion exchanged in one step to achieve desired stress profiles.

[0238] Table 4 shows the CS, DOL, and CT example ion exchanged glass articles EA76-EA90 formed by ion exchanging glass articles having a thickness of 0.6 mm and made from example glass compositions, as indicated in Table 4, in a first ion exchange step at a temperature of 600? C. for 4, 9, and 16 hours in a 18.2% NaNO.sub.3/54.9% KNO.sub.3/6.6% Na.sub.2SO.sub.4/20.3% K.sub.2SO.sub.4 molten salt bath.

TABLE-US-00004 TABLE 4 Example EA76 EA77 EA78 EA79 EA80 Composition E38 E39 E40 E42 E43 4 hours CS (MPa) 385 394 387 396 413 DOL (?m) 84 77 81 81 74 CT (MPa) 53 49 50 55 50 Example EA81 EA82 EA83 EA84 EA85 Composition E38 E39 E40 E42 E43 9 hours CS (MPa) 408 305 396 373 315 DOL (?m) 107 103 116 120 102 CT (MPa) 69 68 76 75 69 Example EA86 EA87 EA88 EA89 EA90 Composition E38 E39 E40 E42 E43 16 hours CS (MPa) 404 408 306 DOL (?m) 146 143 120 CT (MPa) 102 87 100 99 94

[0239] As indicated by the example ion exchanged glass articles in Table 4, glass articles formed from the glass compositions having increased Young's Modulus and K.sub.Ic fracture toughness as described herein may be ion exchanged in a single step to achieve desired stress profiles.

[0240] Table 5 shows the CS, DOL, and CT example ion exchanged glass articles EA91-EA96 formed by ion exchanging glass articles having a thickness of 0.6 mm and made from example glass compositions, as indicated in Table 5, in a first ion exchange step at a temperature of 600? C. for 4, 9, and 16 hours in a 18.2% NaNO.sub.3/54.9% KNO.sub.3/6.6% Na.sub.2SO.sub.4/20.3% K.sub.2SO.sub.4 molten salt bath. Table 5 also shows the CS, DOL, DOC, CT, Knee, and Knee Stress of the glass articles achieved by subjecting the glass articles to a second ion exchange step at a temperature of 410? C. for 1 hour. DOL, Knee, and Knee Stress were measured by RNF.

TABLE-US-00005 TABLE 5 Example EA91 EA92 Composition E3 E4 Step 1-4 hours CS (MPa) 403 371 DOL (?m) 95 118 CT (MPa) 80 97 Step 2-1 hour CS (MPa) 706 641 Knee (?m) 12 13 Knee Stress (MPa) 332 318 DOC (?m) 70 78 CT (MPa) 89 107 Example EA93 EA94 Composition E3 E4 Step 1-9 hours CS (MPa) 348 323 DOL (?m) 137 165 CT (MPa) 115 142 Step 2-1 hour CS (MPa) 653 567 Knee (?m) 12 16 Knee Stress (MPa) 307 254 DOC (?m) 93 101 CT (MPa) 125 149 Example EA95 EA96 Composition E3 E4 Step 1-16 hours CS (MPa) 290 243 DOL (?m) 209 248 CT (MPa) 159 168 Step 2-1 hour CS (MPa) 602 507 Knee (?m) 14 Knee Stress (MPa) 244 DOC (?m) 112 CT (MPa) 169 184

[0241] As indicated by the example ion exchanged glass articles in Table 5, glass articles formed from the glass compositions having increased Young's Modulus and K.sub.Ic fracture toughness as described herein may be ion exchanged in two steps to achieve desired stress profiles.

[0242] Table 6 shows the CS, DOL, and CT of example ion exchanged glass articles EA97-EA120 formed by ion exchanging glass articles having a thickness of 0.8 mm and made from example glass compositions, as indicated in Table 6, in a first ion exchange step at a temperature of 600? C. for 4, 9, and 16 hours in a 18.2% NaNO.sub.3/54.9% KNO.sub.3, 6.6% Na.sub.2SO.sub.4, 20.3% K.sub.2SO.sub.4 molten salt bath. Table 6 also shows the CS, DOL, DOC, CT, Knee, and Knee Stress of the glass articles achieved by subjecting the glass articles to a second ion exchange step at a temperature of 410? C. for 1 hour. DOL, Knee, and Knee Stress were measured by RNF.

TABLE-US-00006 TABLE 6 Example EA97 EA98 EA99 EA100 Composition E20 E22 E23 E24 Step 1-4 hours CS (MPa) 409 389 401 373 DOL (?m) 128 139 127 134 CT (MPa) 71 77 68 69 Step 2-1 hour CS (MPa) 840 802 827 852 Knee (?m) 18 22 15 14 Knee Stress (MPa) 332 305 346 330 DOC (?m) 95 101 101 87 CT (MPa) 78 79 76 78 Example EA101 EA102 EA103 EA104 Composition E20 E22 E23 E24 Step 1-9 hours CS (MPa) 345 324 329 346 DOL (?m) 204 209 220 205 CT (MPa) 92 94 100 83 Step 2-1 hour CS (MPa) 825 826 813 880 Knee (?m) 14 22 19 14 Knee Stress (MPa) 249 255 304 220 DOC (?m) 124 127 134 129 CT (MPa) 83 93 97 87 Example EA105 EA106 EA107 EA108 Composition E20 E22 E23 E24 Step 1-16 hours CS (MPa) 249 263 265 237 DOL (?m) 242 276 281 262 CT (MPa) 123 125 135 135 Step 2-1 hour CS (MPa) 786 763 755 777 Knee (?m) 20 21 16 20 Knee Stress (MPa) 214 233 253 218 DOC (?m) 158 167 169 154 CT (MPa) 132 149 140 140

[0243] As indicated by the example ion exchanged glass articles in Table 6, glass articles formed from the glass compositions having increased Young's Modulus and K.sub.Ic fracture toughness as described herein may be ion exchanged in two steps to achieve desired stress profiles.

[0244] Table 7 shows the DOC and CT of example ion exchanged glass articles EA109-EA123 formed by ion exchanging glass articles having a thickness of 0.5 mm and made from example glass compositions, as indicated in Table 7, at a temperature of 600? C. for 16 hours or 25 hours in each of a 88.5% KNO.sub.3/11.5% K.sub.2SO.sub.4 molten salt bath, 8.2% NaNO.sub.3/74.1% KNO.sub.3/1.7% Na.sub.2SO.sub.4/16.0% K.sub.2SO.sub.4 molten salt bath, 14.6% NaNO.sub.3/58.5% KNO.sub.3/5.3% Na.sub.2SO.sub.4/21.6% K.sub.2SO.sub.4 molten salt bath, 22.0% NaNO.sub.3/51.2% KNO.sub.3/7.9% Na.sub.2SO.sub.4/18.9% K.sub.2SO.sub.4 molten salt bath, and 29.3% NaNO.sub.3/44.0% KNO.sub.3/10.5% Na.sub.2SO.sub.4/16.2% K.sub.2SO.sub.4 molten salt bath.

TABLE-US-00007 TABLE 7 Example EA109 EA110 EA111 Composition E34 E72 E78 16 hours | 88.5% KNO.sub.3/11.5% K.sub.2SO.sub.4 CT (MPa) 274 176 121 25 hours | 88.5% KNO.sub.3/11.5% K.sub.2SO.sub.4 CT (MPa) 291 207 128 Example EA112 EA113 EA114 Composition E34 E72 E78 16 hours | 8.2% NaNO.sub.3/74.1% KNO.sub.3/ 1.7% Na.sub.2SO.sub.4/16.0% K.sub.2SO.sub.4 DOC (?m) 55 CT (MPa) 178 103 69 25 hours | 8.2% NaNO.sub.3, 74.1% KNO.sub.3, 1.7% Na.sub.2SO.sub.4, 16.0% K.sub.2SO.sub.4 DOC (?m) 88 64 CT (MPa) 217 124 87 Example EA115 EA116 EA117 Composition E34 E72 E78 16 hours | 14.6% NaNO.sub.3/58.5% KNO.sub.3/ 5.3% Na.sub.2SO.sub.4/21.6% K.sub.2SO.sub.4 DOL (?m) 157 DOC (?m) 101 74 55 CT (MPa) 150 81 53 25 hours | 14.6% NaNO.sub.3/58.5% KNO.sub.3/ 5.3% Na.sub.2SO.sub.4/21.6% K.sub.2SO.sub.4 DOL (?m) 188 DOC (?m) 122 86 65 CT (MPa) 173 97 71 Example EA118 EA119 Composition E34 E72 16 hours | 22.0% NaNO.sub.3/51.2% KNO.sub.3/ 7.9% Na.sub.2SO.sub.4/18.9% K.sub.2SO.sub.4 DOL (?m) 151 DOC (?m) 103 69 CT (MPa) 116 57 25 hours | 22.0% NaNO.sub.3/51.2% KNO.sub.3/ 7.9% Na.sub.2SO.sub.4/18.9% K.sub.2SO.sub.4 DOL (?m) 171 DOC (?m) 112 80 Example EA120 Composition E34 16 hours | 29.3% NaNO.sub.3/44.0% KNO.sub.3/ 10.5% Na.sub.2SO.sub.4/16.2% K.sub.2SO.sub.4 DOL (?m) 143 DOC (?m) 98 CT (MPa) 85 25 hours | 29.3% NaNO.sub.3/44.0% KNO.sub.3/ 10.5% Na.sub.2SO.sub.4/16.2% K.sub.2SO.sub.4 DOL (?m) 162 DOC (?m) 106 CT (MPa) 112

[0245] As indicated by the example ion exchanged glass articles in Table 7, glass articles formed from the glass compositions having increased Young's Modulus and K.sub.Ic fracture toughness as described herein may be ion exchanged in two steps to achieve desired stress profiles.

[0246] Table 8 shows the DOC and CT of example ion exchanged glass articles EA121-EA131 formed by ion exchanging glass articles having a thickness of 0.6 mm and made from example glass compositions, as indicated in Table 8, in a first ion exchange step at a temperature of 600? C. 16 hours or 25 hours in each of a 88.5% KNO.sub.3/11.5% K.sub.2SO.sub.4 molten salt bath, 8.2% NaNO.sub.3/74.1% KNO.sub.3/1.7% Na.sub.2SO.sub.4/16.0% K.sub.2SO.sub.4 molten salt bath, 14.6% NaNO.sub.3/58.5% KNO.sub.3/5.3% Na.sub.2SO.sub.4/21.6% K.sub.2SO.sub.4 molten salt bath, 22.0% NaNO.sub.3/51.2% KNO.sub.3/7.9% Na.sub.2SO.sub.4/18.9% K.sub.2SO.sub.4 molten salt bath, and 29.3% NaNO.sub.3/44.0% KNO.sub.3/10.5% Na.sub.2SO.sub.4/16.2% K.sub.2SO.sub.4 molten salt bath.

TABLE-US-00008 TABLE 8 Example EA121 EA122 EA123 Composition E34 E72 E78 16 hours | 88.5% KNO.sub.3/11.5% K.sub.2SO.sub.4 DOL (um) 187 DOC (?m) 128 90 68 CT (MPa) 219 121 99 25 hours | 88.5% KNO.sub.3/11.5% K.sub.2SO.sub.4 DOC (?m) 97 80 CT (MPa) 276 141 120 Example EA124 EA125 EA126 Composition E34 E72 E78 16 hours | 8.2% NaNO.sub.3/74.1% KNO.sub.3/ 1.7% Na.sub.2SO.sub.4/16.0% K.sub.2SO.sub.4 DOL (um) 177 DOC (?m) 116 80 60 CT (MPa) 154 80 62 25 hours | 8.2% NaNO.sub.3/74.1% KNO.sub.3/ 1.7% Na.sub.2SO.sub.4/16.0% K.sub.2SO.sub.4 DOL (?m) 222 DOC (?m) 136 94 69 CT (MPa) 192 97 72 Example EA127 EA128 Composition E34 E72 16 hours | 14.6% NaNO.sub.3/58.5% KNO.sub.3/ 5.3% Na.sub.2SO.sub.4/21.6% K.sub.2SO.sub.4 DOL (?m) 161 DOC (?m) 110 74 CT (MPa) 114 67 25 hours | 14.6% NaNO.sub.3/58.5% KNO.sub.3/ 5.3% Na.sub.2SO.sub.4/21.6% K.sub.2SO.sub.4 DOL (?m) 194 DOC (?m) 128 89 CT (MPa) 135 74 Example EA129 EA130 Composition E34 E72 16 hours | 22.0% NaNO.sub.3/51.2% KNO.sub.3/ 7.9% Na.sub.2SO.sub.4/18.9% K.sub.2SO.sub.4 DOL (?m) 142 DOC (?m) 106 72 CT (MPa) 87 46 Example EA131 Composition E34 16 hours | 29.3% NaNO.sub.3/44.0% KNO.sub.3/ 10.5% Na.sub.2SO.sub.4/16.2% K.sub.2SO.sub.4 DOL (?m) 120 DOC (?m) 103 CT (MPa) 68

[0247] As indicated by the example ion exchanged glass articles in Table 8, glass articles formed from the glass compositions having increased Young's Modulus and K.sub.Ic fracture toughness as described herein may be ion exchanged in two steps to achieve desired stress profiles.

[0248] Table 9 shows the DOC and CT of example ion exchanged glass articles EA132 and EA133 formed by ion exchanging glass articles having a thickness of 0.5 mm and made from example glass compositions, as indicated in Table 9, in a first ion exchange step at a temperature of 600? C. 22 and 16 hours in each of a 29.3% NaNO.sub.3/44.0% KNO.sub.3/10.5% Na.sub.2SO.sub.4/16.2% K.sub.2SO.sub.4 molten salt bath and 25.6% NaNO.sub.3/47.6 KNO.sub.3/9.2% Na.sub.2SO.sub.4/17.6% K.sub.2SO.sub.4 molten salt bath, respectively. Table 9 also shows the DOC and CT of the glass articles achieved by subjecting the glass articles to a second ion exchange step at a temperature of 370? C. for 0.25 hours in a 100% KNO.sub.3 molten salt bath.

TABLE-US-00009 TABLE 9 Example EA132 Composition E34 Step 1-22 hours | 29.3% NaNO.sub.3/44.0% KNO.sub.3/ 10.5% Na.sub.2SO.sub.4/16.2% K.sub.2SO.sub.4 DOC (?m) 109 CT (MPa) 95 Step 2-0.25 hours | 100% KNO.sub.3 Knee (?m) 6 Knee Stress (MPa) 135 DOC (?m) 103 CT (MPa) 100 Example EA133 Composition E34 Step 1-16 hours | 25.6% NaNO.sub.3/47.6 KNO.sub.3/ 9.2% Na.sub.2SO.sub.4/17.6% K.sub.2SO.sub.4 DOC (?m) 100 CT (MPa) 97 Step 2-0.25 hours | 100% KNO.sub.3 Knee (?m) 7 Knee Stress (MPa) 143 DOC (?m) 98 CT (MPa) 91

[0249] As indicated by the example ion exchanged glass articles in Table 9, a glass article formed from the glass composition having increased Young's Modulus and K.sub.Ic fracture toughness as described herein may be ion exchanged in two steps to achieve desired stress profiles.

[0250] Referring now to FIG. 7, the stress profile of glass article EA133 having a thickness 0.5 mm were compared to the stress profiles of C1 and C2. The graph shows that after the 600? C. ion exchange step, the C1 and C2 examples exhibit more stress relaxation than E140. C1 and C2 have strain points of 553? C. and 572? C., respectively. Without wishing to be bound by any theory, it is believed that the relatively low strain points of C1 and C2 resulted in stress relaxation of C1 and C2. In contrast, E133, having a strain point of 690? C., did not show the same undesirable amount of stress relaxation. The relatively high strain point is at least partially the result of the relatively high alumina content. For example, E133 contains 19.05 mol % alumina, while C1 and C2 contain 10.29 mol % and 12.69 mol % alumina, respectively. Additionally, the relatively high strain is also at least partially attributed to the high alkaline earth oxide content of the glass, such as CaO and MgO. For example, E133 contains a combined CaO and MgO content of 7.96 mol %. In contrast, C1 and C2 contain CaO and MgO in amounts of 6.33 mol % and 2.40 mol %, respectively. The alumina content and alkaline-earth content of the compositions disclosed herein, such as E133, allow for highly polymerized glass networks to form with higher bond strengths, which yields higher strain points, resulting in the knee region seen in the stress profile of E133 of FIG. 7.

[0251] Referring now to FIG. 8, the stress profile of glass articles EA127, EA129, and EA131 with 0.5 mm thickness are comparatively displayed. The glass articles were ion exchanged at 600? C. for 16 hours in each of a 14.6% NaNO.sub.3/58.5% KNO.sub.3/5.3% Na.sub.2SO.sub.4/21.6% K.sub.2SO.sub.4 molten salt bath, 22.0% NaNO.sub.3/51.2% KNO.sub.3/7.9% Na.sub.2SO.sub.4/18.9% K.sub.2SO.sub.4 NaNO.sub.3 molten salt bath, and 29.3% NaNO.sub.3/44.0% KNO.sub.3/10.5% Na.sub.2SO.sub.4/16.2% K.sub.2SO.sub.4 molten salt bath, respectively. As shown in FIG. 8, all of the glass articles included a knee region.

[0252] As shown in FIG. 9A, the glass article EA118 was frangible. Referring now to FIG. 9B, the glass article EA120 was non-frangible. Both EA118 and EA120 were both formed from example glass composition E34, but subjected to different molten salt baths. As indicated by the examples ion exchanged glass articles in FIGS. 9A and 9B, a glass article formed from a glass composition having increased Young's Modulus and K.sub.Ic fracture toughness as described herein may be subjected to various ion exchange conditions to produced non-frangible glass articles.

[0253] Table 10 below shows EA134 after being ion exchanged at 600? C. for 16 hours in a 25.6% NaNO.sub.3/47.6 KNO.sub.3/9.2% Na.sub.2SO.sub.4/17.6% K.sub.2SO.sub.4 molten salt bath.

TABLE-US-00010 TABLE 10 Example EA134 Composition E34 16 hours | 25.6% NaNO.sub.3/47.6 KNO.sub.3/ 9.2% Na.sub.2SO.sub.4/17.6% K.sub.2SO.sub.4 DOL (?m) 146 DOC (?m) 100 CT (MPa) 97

[0254] As indicated by the example ion exchanged glass articles in Table 10, a glass article formed from the glass composition having increased Young's Modulus and K.sub.Ic fracture toughness as described herein may be ion exchanged in two steps to achieve desired stress profiles.

[0255] Referring now to FIG. 10, the stress profile of EA134 is shown. As shown in FIG. 10, the glass article EA134 has a knee region. FIG. 11 shows the glass article EA134 is borderline frangible.

[0256] Table 11 below shows glass articles EA121 and EA135-EA138 when subjected to a varying time of 16, 19, 22, and 25 hours at 600? C. in a 29.3% NaNO.sub.3/44.0% KNO.sub.3/10.5% Na.sub.2SO.sub.4/16.2% K.sub.2SO.sub.4 molten salt bath.

TABLE-US-00011 TABLE 11 IOX Time (hours) 16 19 22 22 25 Example EA120 EA135 EA136 EA137 EA138 Composition E34 DOL (?m) 143 153 160 154 162 DOC (?m) 98 102 109 107 106 CT (MPa) 85 90 95 88 112

[0257] As indicated by the example ion exchanged glass articles in Table 11, a glass article formed from the glass composition having increased Young's Modulus and K.sub.Ic fracture toughness as described herein may be ion exchanged in two steps to achieve desired stress profiles.

[0258] Referring now to FIG. 12, the stress profile of EA136 is shown. As shown in FIG. 12, the glass article EA136 has a knee region. FIG. 13A shows the glass article EA136 is borderline frangible. FIG. 13B shows the glass article EA137 is also borderline frangible.

[0259] Referring now to FIG. 14, the stress profile of glass articles EA121, EA124, EA127, EA 129, and EA131 with 0.6 mm thickness are comparatively displayed. The glass articles were ion exchanged at 600? C. for 16 hours in each of a 88.5% KNO.sub.3/11.5% K.sub.2SO.sub.4 molten salt bath, 8.2% NaNO.sub.3/74.1% KNO.sub.3/1.7% Na.sub.2SO.sub.4/16.0% K.sub.2SO.sub.4 molten salt bath, 14.6% NaNO.sub.3/58.5% KNO.sub.3/5.3% Na.sub.2SO.sub.4/21.6% K.sub.2SO.sub.4 molten salt bath, 22.0% NaNO.sub.3/51.2% KNO.sub.3/7.9% Na.sub.2SO.sub.4/18.9% K.sub.2SO.sub.4 molten salt bath, and 29.3% NaNO.sub.3/44.0% KNO.sub.3/10.5% Na.sub.2SO.sub.4/16.2% K.sub.2SO.sub.4 molten salt bath, respectively. As shown in FIG. 14, all of the glass articles included a knee region.

[0260] As shown in FIG. 15A, the glass article EA129 was frangible. Referring now to FIG. 15B, the glass article EA131 was non-frangible. Both EA129 and EA131 were both formed from example glass composition E34, but subjected to different molten salt baths. As indicated by the examples ion exchanged glass articles in FIGS. 14A and 14B, a glass article formed from a glass composition having increased Young's Modulus and K.sub.Ic fracture toughness as described herein may be subjected to various ion exchange conditions to produce non-frangible glass articles.

[0261] Referring now to FIG. 16, the stress profile of EA129 is shown. As shown in FIG. 16, the article EA133 has a knee region.

[0262] Table 12 below shows glass articles EA139 when subjected to an ion exchange time of 20 hours at 600? C. in a 25.6% NaNO.sub.3/47.6 KNO.sub.3/9.2% Na.sub.2SO.sub.4/17.6% K.sub.2SO.sub.4 molten salt bath.

TABLE-US-00012 TABLE 12 IOX Time (hours) 20 Example EA139 Composition E34 DOL (?m) 145 DOC (?m) 112 CT (MPa) 94

[0263] As indicated by the example ion exchanged glass articles in Table 12, a glass article formed from the glass composition having increased Young's Modulus and K.sub.Ic fracture toughness as described herein may be ion exchanged in two steps to achieve desired stress profiles. RNF was used to measure the DOL value reported in Table 12.

[0264] Referring now to FIG. 17 the stress profile of EA139 is shown. As shown in FIG. 17, the article EA139 has a knee region. FIG. 18 shows the glass article EA139 is borderline frangible.

[0265] Referring now to FIG. 19, example ion exchanged glass articles EA140 and EA141 were formed by ion exchanging glass articles having a thickness of 0.5 mm and made from example glass compositions E34 and E80, respectively, for a first ion exchange in a 25.6% NaNO.sub.3/47.6 KNO.sub.3/9.2% Na.sub.2SO.sub.4/17.6% K.sub.2SO.sub.4 molten salt bath at 600? C. for 16 hours and then second ion exchange in a 100% KNO.sub.3 molten salt bath at 370? C. for 0.17 hour (10 minutes). Table 13 shows the DOC, CT, Knee, and Knee Stress of ion exchanged glass articles EA140 and EA141. Knee and Knee Stress were measured by RNF.

TABLE-US-00013 TABLE 13 Example EA140 EA141 Composition E34 E80 Knee (?m) 8 7 Knee Stress (MPa) 172 167 DOC (?m) 97 88 CT (MPa 101 89

[0266] Example glass composition E34, a glass composition including 0.24 mol % P.sub.2O.sub.5, had a liquidus viscosity 60? C. less than example glass composition E80, a glass composition including 0 mol % P.sub.2O.sub.5. Moreover, example ion exchanged glass article EA140, formed from example glass composition E34 including 0.24 mol % P.sub.2O.sub.5, had a greater DOC and CT than example ion exchanged glass article EA141, formed from example glass composition E80 including 0 mol % P.sub.2O.sub.5. While not wishing to be bound by theory, it is believed that the relatively increased DOC and CT of example ion exchanged glass article EA140 was imparted by P.sub.2O.sub.5 increasing the diffusivity of the glass article.

[0267] It will be apparent to those skilled in the art that various modifications and variations may be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Thus, it is intended that the specification cover the modifications and variations of the various embodiments described herein provided such modification and variations come within the scope of the appended claims and their equivalents.