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

A method for melting and/or refining glass, glass ceramic or glass which can be ceramized to form glass ceramic includes: providing a batch of raw materials; heating the batch until a melt of molten glass is obtained, the batch being heated at least in sections to a temperature above T3 which corresponds to a viscosity of the molten glass of 10.sup.3 dPa*s; refining the melt, the melt being heated at least in sections to a temperature above T2.5 which corresponds to a viscosity of the molten glass of 10.sup.2.5 dPa*s, refining of the melt includes adjusting an oxygen partial pressure p(O.sub.2) which is reduced by at least 60% relative to an O.sub.2 saturation in the melt at temperature T3; and obtaining a re-fined glass, a refined glass ceramic or a refined glass which can be ceramized to form glass ceramic.

A method for melting and/or refining glass, glass ceramic or glass which can be ceramized to form glass ceramic includes: providing a batch of raw materials; heating the batch until a melt of molten glass is obtained, the batch being heated at least in sections to a temperature above T3 which corresponds to a viscosity of the molten glass of 10.sup.3 dPa*s; refining the melt, the melt being heated at least in sections to a temperature above T2.5 which corresponds to a viscosity of the molten glass of 10.sup.2.5 dPa*s, refining of the melt includes adjusting an oxygen partial pressure p(O.sub.2) which is reduced by at least 60% relative to an O.sub.2 saturation in the melt at temperature T3; and obtaining a re-fined glass, a refined glass ceramic or a refined glass which can be ceramized to form glass ceramic.

According to one embodiment, a glass-ceramic composition may include from about 60 mol. % to about 75 mol. % SiO.sub.2; from about 5 mol. % to about 10 mol. % Al.sub.2O.sub.3; from about 2 mol. % to about 20 mol. % alkali oxide R.sub.2O, the alkali oxide R.sub.2O including Li.sub.2O and Na.sub.2O; and from 0 mol. % to about 5 mol. % alkaline earth oxide RO, the alkaline earth oxide RO including MgO. A ratio of Al.sub.2O.sub.3 (mol. %) to the sum of (R.sub.2O (mol. %)+RO (mol. %)) may be less than 1 in the glass-ceramic composition. A major crystalline phase of the glass-ceramic composition may be Li.sub.2Si.sub.2O.sub.5. A liquidus viscosity of the glass-ceramic composition may be greater than 35 kP. The glass-ceramic composition may be used to form the glass clad layer(s) of a laminated glass article.

According to one embodiment, a glass-ceramic composition may include from about 60 mol. % to about 75 mol. % SiO.sub.2; from about 5 mol. % to about 10 mol. % Al.sub.2O.sub.3; from about 2 mol. % to about 20 mol. % alkali oxide R.sub.2O, the alkali oxide R.sub.2O including Li.sub.2O and Na.sub.2O; and from 0 mol. % to about 5 mol. % alkaline earth oxide RO, the alkaline earth oxide RO including MgO. A ratio of Al.sub.2O.sub.3 (mol. %) to the sum of (R.sub.2O (mol. %)+RO (mol. %)) may be less than 1 in the glass-ceramic composition. A major crystalline phase of the glass-ceramic composition may be Li.sub.2Si.sub.2O.sub.5. A liquidus viscosity of the glass-ceramic composition may be greater than 35 kP. The glass-ceramic composition may be used to form the glass clad layer(s) of a laminated glass article.

In embodiments, a precursor glass composition comprises from about 55 wt. % to about 80 wt. % SiO.sub.2; from about 2 wt. % to about 20 wt. % Al.sub.2O.sub.3; from about 5 wt. % to about 20 wt. % Li.sub.2O; greater than 0 wt % to about 3 wt. % Na.sub.2O; a non-zero amount of P.sub.2O.sub.5 less than or equal to 4 wt. %; and from about 0.2 wt. % to about 15 wt. % ZrO.sub.2. In embodiments, ZrO.sub.2 (wt. %)+P.sub.2O.sub.5 (wt. %) is greater than 3. When the precursor glass composition is converted to a glass-ceramic article, the glass-ceramic article may include grains having a longest dimension of less than 100 nm.

In embodiments, a precursor glass composition comprises from about 55 wt. % to about 80 wt. % SiO.sub.2; from about 2 wt. % to about 20 wt. % Al.sub.2O.sub.3; from about 5 wt. % to about 20 wt. % Li.sub.2O; greater than 0 wt % to about 3 wt. % Na.sub.2O; a non-zero amount of P.sub.2O.sub.5 less than or equal to 4 wt. %; and from about 0.2 wt. % to about 15 wt. % ZrO.sub.2. In embodiments, ZrO.sub.2 (wt. %)+P.sub.2O.sub.5 (wt. %) is greater than 3. When the precursor glass composition is converted to a glass-ceramic article, the glass-ceramic article may include grains having a longest dimension of less than 100 nm.

A glass-ceramic comprising, in weight percent on an oxide basis, of 50 to 70% SiO.sub.2, 0 to 20% Al.sub.2O.sub.3, 12 to 23% MgO, 0 to 4% Li.sub.2O, 0 to 10% Na.sub.2O, 0 to 10% K.sub.2O, 0 to 5% ZrO.sub.2, and 2 to 12% F, wherein the predominant crystalline phase of said glass-ceramic is a trisilicic mica, a tetrasilicic mica, or a mica solid solution between trisilicic and tetrasilicic, and wherein the total of Na.sub.2O+Li.sub.2O is at least 2 wt. %; wherein the glass-ceramic can be ion-exchanged.

A glass-ceramic comprising, in weight percent on an oxide basis, of 50 to 70% SiO.sub.2, 0 to 20% Al.sub.2O.sub.3, 12 to 23% MgO, 0 to 4% Li.sub.2O, 0 to 10% Na.sub.2O, 0 to 10% K.sub.2O, 0 to 5% ZrO.sub.2, and 2 to 12% F, wherein the predominant crystalline phase of said glass-ceramic is a trisilicic mica, a tetrasilicic mica, or a mica solid solution between trisilicic and tetrasilicic, and wherein the total of Na.sub.2O+Li.sub.2O is at least 2 wt. %; wherein the glass-ceramic can be ion-exchanged.

The present invention relates to a spinel glass-ceramic made from a composition with the components 25 to 50% by weight SiO.sub.2, 10 to 35% by weight Al.sub.2O.sub.3, 1 to 15% by weight MgO, 1 to 15% by weight P.sub.2O.sub.5, 1 to 25% by weight ZrO.sub.2 and/or TiO.sub.2, 0 to 20% by weight La.sub.2O.sub.3, 0 to 10% by weight B.sub.2O.sub.3, and 0 to 15% by weight additives. The spinel glass-ceramic contains at least one spinel phase, but no high quartz solid solution phase. The glass-ceramic according to the invention exhibits very high mechanical stability, for example, very high flexural strength, wherein its optical properties can be simultaneously adjusted. In addition, the present invention also relates to a method for producing and the use of the spinel glass-ceramic. Furthermore, the present invention relates to a shaped dental product containing the spinel glass-ceramic.