A Li.sub.2O—Al.sub.2O.sub.3—SiO.sub.2-based crystallized glass contains: in a mass basis, SnO.sub.2: 0% to 5%; and HfO.sub.2+Ta.sub.2O.sub.5: 0.01% to 10%.

A glass-ceramic article comprises: a center-volume composition comprising (on an oxide basis): 55-75 mol % SiO.sub.2; 0.2-10 mol % Al.sub.2O.sub.3; 0-5 mol % B.sub.2O.sub.3; 15-30 mol % Li.sub.2O; 0-2 mol % Na.sub.2O; 0-2 mol % K.sub.2O; 0-5 mol % MgO; 0-2 mol % ZnO; 0.2-3.0 mol % P.sub.2O.sub.5; 0.1-10 mol % ZrO.sub.2; 0-4 mol % TiO.sub.2; and 0-1.0 mol % SnO.sub.2. Lithium disilicate and either β-spodumene or β-quartz are the two predominant crystalline phases (by weight) of the glass-ceramic article. The glass-ceramic article further comprises tetragonal ZrO.sub.2 as a crystalline phase. The composition of the glass-ceramic article from a primary surface into a thickness of the glass-ceramic article can comprise over 10 mol % Na.sub.2O (on an oxide basis), with the mole percentage of Na.sub.2O decreasing from the primary surface towards the center-volume. The glass-ceramic article exhibits a ring-on-ring load-to-failure of at least 120 kgf, when the thickness of the glass-ceramic article is 0.3 mm to 2.0 mm.

Sheet-like glass ceramic article are provided that include surfaces with a thickness between the surfaces between 0.5 mm and 1.9 mm and a core. The articles have a first microstructure provided on each of the surfaces and have a second microstructure in the core with a second thickness (d.sub.2). The first microstructures extend inwardly from the surfaces towards the core and has a first thickness (d.sub.1). The first microstructure has a difference from the second microstructure selected from a group consisting of: a crystalline phase type, a crystalline phase amount, crystalline phase size distribution, crystalline phase orientation, crystalline phases composition, crystalline inclusion, an amorphous phase type, an amorphous phase percentage amount, an amorphous phase composition, and any combinations thereof. The difference results in a first coefficient of linear thermal expansion of the first microstructure that is smaller than a second coefficient of linear thermal expansion of the second microstructure.

A method for determining crystal phases of a glass ceramic sample, including the steps of applying energy to the sample using an excitation source, detecting raw Raman spectral energy that is given off by the sample using a detector, wherein the raw Raman spectral energy includes peak values, determining a plurality of predetermined energy peaks based off a composition of the sample, superimposing the plurality of predetermined energy peaks over the raw Raman spectral energy, applying a baseline value between each predetermined energy peak, subtracting the baseline value from the raw Raman spectral energy, calculating corrected peak values based on the raw Raman spectral energy and baseline value, and determining the crystal phases of the glass ceramic sample based on the corrected peak values.

The present applicationprovides transparent glass-ceramics of lithium aluminosilicate type, of β-quartz, the composition of which contains a low content of lithium, articles constituted at least in part by said glass-ceramics, precursor glasses for said glass-ceramics, and also a method of preparing said articles. Said glass-ceramics have a composition, expressed in percentages by weight of oxide, containing63% to 67.5% of SiO.sub.2; 18% to 21% of Al.sub.2O.sub.3; 2% to 2.9% of Li.sub.2O; 0 to 1.5% of MgO; 1% to 3.2% of ZnO; 0 to 4% of BaO; 0 to 4% of SrO; 0 to 2% of CaO; 2% to 5% of TiO.sub.2; 0 to 3% of ZrO.sub.2; 0 to 1% of Na.sub.2O; 0 to 1% of K.sub.2O; 0 to 5% of P.sub.2O.sub.5; with (0.74 MgO+0.19 BaO+0.29 SrO+0.53 CaO+0.48 Na.sub.2O+0.32 K.sub.2O)/Li.sub.2O<0.9; optionally up to 2% of at least one fining agent; and optionally up to 2% of at least one coloring agent.

Ion-exchanged glass ceramic articles described herein have a stress that decreases with increasing distance according to a substantially linear function from a depth of about 0.07t to a depth of about 0.26t from the outer surface of the ion-exchanged glass ceramic article from a compressive stress to a tensile stress. The stress transitions from the compressive stress to the tensile stress at a depth of from about 0.18t to about 0.25t from the outer surface of the ion-exchanged glass ceramic article. An absolute value of a maximum compressive stress at the outer surface of the ion-exchanged glass article is from 1.8 to 2.2 times an absolute value of a maximum central tension (CT) of the ion-exchanged glass article, and the glass ceramic article has a fracture toughness of 1 MPa√m or more as measured according to the double cantilever beam method.

A transparent gahnite-spinel glass ceramic is provided. The glass ceramic includes a first crystal phase including (Mg.sub.xZn.sub.1−x)Al.sub.2O.sub.4 where x is less than 1 and a second crystal phase including tetragonal ZrO.sub.2. The glass ceramic may be ion exchanged. Methods for producing the glass ceramic are also provided.

A composition includes 30 mol % to 60 mol % SiO.sub.2; 15 mol % to 40 mol % Al.sub.2O.sub.3; 5 mol % to 25 mol % Y.sub.2O.sub.3; 5 mol % to 15 mol % TiO.sub.2; and 0.1 mol % to 15 mol % RO, such that RO is a sum of MgO, CaO, SrO, and BaO.

The present invention provides a microcrystalline glass product. The microcrystalline glass product includes the following components in percentage by weight: SiO.sub.2: 45-70%; Al.sub.2O.sub.3: 8-18%; Li.sub.2O: 10-25%; ZrO.sub.2: 5-15%; P.sub.2O.sub.5: 2-10%; and Y.sub.2O.sub.3: greater than 0 but less than or equal to 8%. Through reasonable component design, the microcrystalline glass and the microcrystalline glass product obtained in the present invention have excellent mechanical and optical properties and are suitable for electronic devices or display devices.

Lithium silicate materials are described which can be easily processed by machining to dental products without undue wear of the tools.