Glass-based articles that include a compressive stress layer extending from a surface of the glass-based article to a depth of compression are formed by exposing glass-based substrates to water vapor containing environments. The glass-based substrates have compositions selected to be fusion formable, to be steam strengthen able, and to avoid the formation of platinum defects during the forming process. The methods of forming the glass-based articles may include elevated pressures and/or multiple exposures to water vapor containing environments.

A laminated glass article has a first layer having a first ion exchange diffusivity, D.sub.0, and a second layer adjacent to the first layer and having a second ion exchange diffusivity, D.sub.1. D.sub.0/D.sub.1 is from about 1.2 to about 10, or D.sub.0/D.sub.1 is from about 0.05 to about 0.95. A method for manufacturing the laminated glass article includes forming a first layer having a first ion exchange diffusivity, D.sub.0, and forming a second layer adjacent to the first layer and having a second ion exchange diffusivity, D.sub.1. The laminated glass article can be strengthened by an ion exchange process to form a strengthened laminated glass article having a compressive stress layer with a depth of layer from about 8 μm to about 100 μm.

Manufacturing methods for making a substantially rectangular and flat glass preform for manufacturing a Li ion conducting glass separator can involve drawing the preform to a thin sheet and may involve one or more of slumping, rolling or casting the glass within a frame that defines a space filling region and therewith the shape and size of the preform. The thickness of the rectangular flat preform so formed may be about 2 mm or less. The frame may be slotted having a back surface and widthwise wall portion that define the height and width of the space filling region. The flat backing surface and surfaces of the widthwise wall portions are defined may be coated by a material that is inert in direct contact with the heated glass material, such as gold.

Glasses that are substantially free of alkalis that possess high annealing points and, thus, good dimensional stability (i.e., low compaction) for use as TFT backplane substrates in amorphous silicon, oxide and low-temperature polysilicon TFT processes.

An aluminosilicate glass, including in mole percent on an oxide basis, MgO+CaO+SrO+Li.sub.2O+ZnO+Y.sub.2O.sub.3+ZrO.sub.2+La.sub.2O.sub.3+TiO.sub.2+Nb.sub.2O.sub.5+Ta.sub.2O.sub.5 in a range of from 5 mol % to 25 mol %. The glass is processable by (i) flowing the glass in a molten state over forming surfaces to form a glass ribbon, the forming surfaces converging at a root and (ii) drawing the glass ribbon using pulling rollers to form a glass sheet, wherein the pulling rollers are spaced at a pulling roller distance from the root, and wherein the glass exhibits a viscosity curve slope obtained by plotting a temperature gradient to increase a root viscosity of the glass at the root, to a higher viscosity at one of several positions between the root and the pulling rollers, and a viscosity of the glass at the pulling rollers. The glass comprises a liquidus viscosity, the root viscosity being less than the liquidus viscosity, and the glass comprising a viscosity curve slope that prevents a baggy warp defect. In certain embodiments, when the root viscosity of the glass is in a range of from about 70 kP to about 90 kP, and the viscosity of the glass at the pulling rollers is greater than 90 kP and less than or equal 1×10.sup.8 kP, the temperature gradient is less than 150° C.

Glass-based articles having defined stress profiles and methods for manufacturing such glass-based articles are provided. A non-limiting glass-based article comprises an outer region extending from the surface to a depth of compression, wherein the outer region is under a neutral stress or a first compressive stress, a core region under a second compressive stress, the second compressive stress defining a compression peak having a maximum compression value and a maximum width at zero stress in a range of from about 1 micrometer to about 200 micrometers, and an intermediate region disposed between the surface and the core region, wherein the intermediate region is under a tensile stress.

A method of making a glass sheet comprises laminating a high CTE core glass to a low CTE clad glass at high temperatures and allowing the laminate to cool creating compressive stress in the clad glass, and then ion exchanging the laminate to increase the compressive stress in the outer near surface regions of the clad glass. The core glass may include ions that exchange with ion in the clad glass to increase the compressive stress in inner surface regions of the clad glass adjacent to the clad glass/core glass interfaces. The glass laminate may be formed and laminated using a fusion forming and laminating process and fusion formable and ion exchangeable glass compositions.

A method of making a glass includes batching constituents, including silica, alumina, boria, magnesia, quicklime, and strontia, where one or more of the constituents is from “dirty” raw material that includes a relatively large amount of sulfur. The method further includes melting and mixing the batch to make glass having sulfur content but free of blisters, suitable for high performance displays.

Thin glass substrates are provided. Also provided are methods and apparatuses for the production thereof and provides a thin glass substrate of improved optical quality. The method includes, after the melting and before a hot forming process, adjusting the viscosity of the glass that is to be formed or has at least partially been formed is in a defined manner for the thin glass substrate to be obtained. The apparatus includes a device for melting, a device for hot forming, and also a device for defined adjustment of the viscosity of the glass to be formed into a thin glass substrate, and the device for defined adjustment of the viscosity of the glass to be formed into a thin glass substrate is arranged upstream of the device for hot forming.

A glass sheet of the present invention has a content of Li.sub.2O+Na.sub.2O+K.sub.2O of from 0 mol % to less than 1.0 mol % and a content of B.sub.2O.sub.3 of from 0 mol % to less than 2.0 mol % in a glass composition, has a β-OH value of less than 0.20/mm, and has a thermal shrinkage ratio of 20 ppm or less when increased in temperature from normal temperature at a rate of 5° C./min, kept at a temperature of 500° C. for 1 hour, and decreased in temperature at a rate of 5° C./min.