Glass-based articles having sections of different thicknesses where a maximum central tension in a thinner section is less than that of a thicker section. The articles comprise an alkali metal oxide having a independent nonzero concentrations that vary along at least a portion of the thickness of each section. Consumer electronic products may comprise the glass-based articles having sections of different thicknesses.

One aspect relates to a process for the preparation of a quartz glass body. The process includes providing a silicon dioxide granulate I prepared from a pyrogenically produced silicon dioxide powder, treating the silicon dioxide granulate I with a reactant at a temperature in a range from 1000 to 1300° C., and making a glass melt out of the silicon dioxide granulate. A quartz glass body is made out of at least a part of the glass melt. Furthermore, one aspect relates to a quartz glass body obtainable by this process. Furthermore, one aspect relates to a light guide, an illuminant, and a formed body, each of which is obtainable by further processing of the quartz glass body. One aspect additionally relates to a process for the preparation of a silicon dioxide granulate II.

Glass-based articles are manufactured by a unique ion exchange process that results in glass-based articles having improved stress profiles with higher stress values at moderate depths. A medium of the ion exchange process includes ions of two or more alkali metals of two or more alkali metal oxides in a base composition of a glass-based substrate in a ratio such that ions of each alkali metal are in chemical equilibrium with each of the respective alkali metals of the alkali metal oxides in the base glass composition.

A vitrifiable feed material for producing flint glass by way of a process that uses submerged combustion melting includes a base glass portion, an oxidizing agent, and a decolorant. The base glass portion includes an SiO.sub.2 contributor, an Na.sub.2O contributor, and a CaO contributor to provide SiO.sub.2, Na.sub.2O, and CaO, respectively, to a glass melt when melted therein. The oxidizing agent may be a sulfate compound in an amount ranging from 0.20 wt % to 0.50 wt % as expressed as SO.sub.3 based on the total weight of the vitrifiable feed material, and the decolorant may be selenium in an amount ranging from 0.008 wt % to 0.016 wt % or manganese oxide in an amount ranging from 0.1 wt % to 0.2 wt % based on the total weight of the vitrifiable feed material.

An alkali-free glass of the present invention includes as a glass composition, in terms of mass %, 55% to 70% of SiO.sub.2, 15% to 25% of Al.sub.2O.sub.3, 0% to 1% of B.sub.2O.sub.3, 0% to 0.5% of Li.sub.2O+Na.sub.2O+K.sub.2O, 2% to 6% of MgO, 2% to 8% of CaO, 0% to 4% of SrO, and 6% to 12% of BaO, and has a strain point of more than 720° C.

A glass has a low ratio of density ρ and refractive index n.sub.d. The glass has a refractive index n.sub.d in a range of 1.80 to 2.00, an internal transmission of at least 80% (450 nm, 10 mm), a dispersion v.sub.d of 19.0 to 27.0, and a ratio ρ/n.sub.d of <1.97.

An alkali-free glass of the present invention includes as a glass composition, in terms of mass %, 55% to 70% of SiO.sub.2, 15% to 25% of Al.sub.2O.sub.3, 0% to 1% of B.sub.2O.sub.3, 0% to 0.5% of Li.sub.2O+Na.sub.2O+K.sub.2O, 2% to 6% of MgO, 2% to 8% of CaO, 0% to 4% of SrO, and 6% to 12% of BaO, and has a strain point of more than 720° C.

A glass substrate and a method for manufacturing the glass substrate are provided. The glass substrate may include a base glass including SiO.sub.2, Al.sub.2O.sub.3, and Li.sub.2O, and nanocrystals having an average diameter in a range from about 5 nm to about 10 nm, thereby exhibiting enhanced surface strength properties while maintaining good transmittance properties. The method may include a step of heat-treating a base glass, thereby providing a glass substrate having enhanced strength properties.

Ion-exchanged alkali aluminosilicate glass articles with a ratio of peak compressive stress value to Young's modulus value of 15 or more. The glass articles may include Al.sub.2O.sub.3 mol %+RO mol %≥17 mol %, where RO mol %=MgO mol %+CaO mol %, and be substantially free of ZnO, SrO, BaO, B.sub.2O.sub.3, P.sub.2O.sub.5, Li.sub.2O, and K.sub.2O. The glass articles may have a peak compressive stress value in a range of 500 MPa to 1300 MPa. The glass articles are suitable for various high-strength applications, including cover glass applications that experience significant bending stresses during use, for example, cover glasses for flexible displays.

A cover glass made of a glass ceramic that is silica based and has a main crystal phase of high quartz solid solution or keatite solid solution is provided. The cover glass has a stress profile with at least one inflection point at a depth of the cover glass of more than 10 μm, a thickness from 0.1 mm to 2 mm, and a chemical tempering structure with a surface compressive stress of at least 250 MPa and at most 1500 MPa. A process for producing the cover glass is provided that includes producing a silica based green glass, hot shaping the silica based green glass, thermally treating the silica based green glass with a nucleation step and a ceramization step, and performing an ion exchange at an exchange bath temperature for a duration of time in an exchange bath.