The present invention relates to a glass including, in terms of mole percentage based on oxides: 50.0 to 75.0% of SiO.sub.2; 7.5 to 25.0% of Al.sub.2O.sub.3; 0 to 25.0% of B.sub.2O.sub.3; 6.5 to 20.0% of Li.sub.2O; 1.5 to 10.0% of Na.sub.2O; 0 to 4.0% of K.sub.2O; 1.0 to 20.0% of MgO; one or more components selected from MgO, CaO, SrO, and BaO in a total amount of 1.0 to 20.0%; and 0 to 5.0% of TiO.sub.2, in which a value of Y calculated based on the following formula is 19.5 or less, Y=1.2×([MgO]+[CaO]+[SrO]+[BaO])+1.6×([Li.sub.2O]+[Na.sub.2O]+[K.sub.2O]), provided that [MgO], [CaO], [SrO], [BaO], [Li.sub.2O], [Na.sub.2O], and [K.sub.2O] are contents, in terms of mole percentage based on oxides, of components of MgO, CaO, SrO, BaO, Li.sub.2O, Na.sub.2O, and K.sub.2O respectively.

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.

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.

The present invention provides a silicate glass that can reduce a color change in base material zirconia even when simultaneously fired with an unsintered zirconia. The present invention also provides a dental product using same. The present invention relates to a silicate glass comprising: 65.0 to 90.0 mol % SiO.sub.2, 4.0 to 15.0 mol % Al.sub.2O.sub.3, 1.0 to 10.0 mol % K.sub.2O, 0.1 to 7.0 mol % Na.sub.2O, and 0.01 to 15.0 mol % CaO, the silicate glass being essentially free of B.sub.2O.sub.3, and satisfying the relation {(number of moles of Al.sub.2O.sub.3)/(total number of moles of RO+R.sub.2O)}≥0.70, wherein R in the metal oxide represented by RO represents a metallic element in group 2 or 12 of the periodic table, and R in the metal oxide represented by R.sub.2O represents a metallic element in group 1 of the periodic table. The present invention also relates to a composite comprising the silicate glass and a base material formed of a ceramic; a sintered body as a fired product of the composite; and a dental product comprising the sintered body.