Glass stack configurations including a carrier plate, setter plates, and glass sheets for thermal treatment of the glass sheets to form glass ceramic articles are provided. The glass stacking configurations and components described herein are selected to improve thermal uniformity throughout a glass stack during ceramming processes while maintaining or even reducing the stresses in the resultant glass ceramic article. Accordingly, the glass ceramic articles made according to the various embodiments described herein exhibit improved optical qualities and less warp than glass ceramic articles made according to conventional processes. Various embodiments of carrier plates, setter plates, parting agent compositions, and methods of stacking glass sheets are described.

Glass stack configurations including a carrier plate, setter plates, and glass sheets for thermal treatment of the glass sheets to form glass ceramic articles are provided. The glass stacking configurations and components described herein are selected to improve thermal uniformity throughout a glass stack during ceramming processes while maintaining or even reducing the stresses in the resultant glass ceramic article. Accordingly, the glass ceramic articles made according to the various embodiments described herein exhibit improved optical qualities and less warp than glass ceramic articles made according to conventional processes. Various embodiments of carrier plates, setter plates, parting agent compositions, and methods of stacking glass sheets are described.

In a known method for producing a quartz glass component, a crystal formation layer containing a crystallization promoter is produced on a coating surface of a base body of quartz glass. Starting therefrom, to provide a method for producing a quartz glass component of improved thermal strength and long-term stability which displays a comparatively small deformation particularly also in the case of rapid heating-up processes, it is suggested according to one aspect that a porous crystal formation layer containing amorphous SiO.sub.2 particles is produced with a mean thickness in the range of 0.1 to 5 mm, and that a substance which contains cesium and/or rubidium is used as the crystallization promoter.

In a known method for producing a quartz glass component, a crystal formation layer containing a crystallization promoter is produced on a coating surface of a base body of quartz glass. Starting therefrom, to provide a method for producing a quartz glass component of improved thermal strength and long-term stability which displays a comparatively small deformation particularly also in the case of rapid heating-up processes, it is suggested according to one aspect that a porous crystal formation layer containing amorphous SiO.sub.2 particles is produced with a mean thickness in the range of 0.1 to 5 mm, and that a substance which contains cesium and/or rubidium is used as the crystallization promoter.

A thermally tempered aluminosilicate glass-ceramic composition includes a crystalline phase and a residual glass phase, wherein the two phases form a system wherein the thermal expansion curve of the system has two distinct sections diverging from an inflection point temperature in the range of about 450° C. to about 600° C., and wherein the difference between coefficient of thermal expansion of the glass-ceramic below and above the inflection point is greater than about 4 ppm/° C.

A method for producing a glass ceramic includes: providing a batch of raw materials; heating the batch of raw materials until a melt is obtained, the batch of raw materials being heated at least in a plurality of sections to a temperature above T3 which corresponds to a viscosity of a molten glass of 10.sup.3 dPa*s; refining the melt, the melt being heated at least in a plurality of sections to a temperature above T2.5 which corresponds to a viscosity of the molten glass of 10.sup.2.5 dPa*s; obtaining a refined glass which is configured for being ceramized to form a glass ceramic material; and ceramizing a glass which is configured for being ceramized to form the glass ceramic material, at least one of the step of heating until the melt is obtained and the step of refining being performed with heating by way of H.sub.2 and O.sub.2 combustion.

A method for producing a glass ceramic includes: providing a batch of raw materials; heating the batch of raw materials until a melt is obtained, the batch of raw materials being heated at least in a plurality of sections to a temperature above T3 which corresponds to a viscosity of a molten glass of 10.sup.3 dPa*s; refining the melt, the melt being heated at least in a plurality of sections to a temperature above T2.5 which corresponds to a viscosity of the molten glass of 10.sup.2.5 dPa*s; obtaining a refined glass which is configured for being ceramized to form a glass ceramic material; and ceramizing a glass which is configured for being ceramized to form the glass ceramic material, at least one of the step of heating until the melt is obtained and the step of refining being performed with heating by way of H.sub.2 and O.sub.2 combustion.

A lithium silicate glass ceramic having lithium metasilicate as main crystal phase and having not more than 30 wt.-% of lithium metasilicate crystals and having the following components in the amounts indicated:

TABLE-US-00001 Component Wt.-% SiO.sub.2 71.0 to 82.0 Li.sub.2O 6.0 to 14.0 Me.sup.I.sub.2O 4.0 to 15.0 Al.sub.2O.sub.3 2.0 to 10.0 P.sub.2O.sub.5 0.5 to 7.0,
wherein Me.sup.I.sub.2O is selected from Na.sub.2O, K.sub.2O, Rb.sub.2O, Cs.sub.2O and mixtures thereof, and
wherein the molar ratio of SiO.sub.2 to Li.sub.2O is in the range of 2.5 to 5.0.

A lithium silicate glass ceramic having lithium metasilicate as main crystal phase and having not more than 30 wt.-% of lithium metasilicate crystals and having the following components in the amounts indicated:

TABLE-US-00001 Component Wt.-% SiO.sub.2 71.0 to 82.0 Li.sub.2O 6.0 to 14.0 Me.sup.I.sub.2O 4.0 to 15.0 Al.sub.2O.sub.3 2.0 to 10.0 P.sub.2O.sub.5 0.5 to 7.0,
wherein Me.sup.I.sub.2O is selected from Na.sub.2O, K.sub.2O, Rb.sub.2O, Cs.sub.2O and mixtures thereof, and
wherein the molar ratio of SiO.sub.2 to Li.sub.2O is in the range of 2.5 to 5.0.

A lithium silicate glass ceramic having lithium metasilicate as main crystal phase and having not more than 30 wt.-% of lithium metasilicate crystals.