Patent ID: 8518842

Claim:
A transparent glass ceramic having low thermal expansion and a composition, in % by weight, based on oxide content, of: SiO 2 35 to 70 Al 2 O 3 17 to 35 Li 2 O 2 to 6 TiO 2 0 to 6 ZrO 2 0 to 6 TiO 2 + ZrO 2 0.5 to 9 ZnO 0.5 to 5, wherein the glass ceramic is produced by fining with SnO 2 and at least one further fining agent selected from the group consisting of Sb 2 O 3 , SO 4 2− , Br − and Cl − ; wherein a molar ratio of the SnO 2 to the at least one further fining agent is from 1:2 to 2:1, wherein the transparent glass ceramic has a thermal expansion coefficient in a range of −0.10·10 −6 /K to +0.10·10 −6 /K in a temperature range of 0° C. to 50° C., and wherein the glass ceramic contains one or more crystal phases selected from the group consisting of high quartz, mixed high quartz crystal, keatite, mixed keatite crystal and β-eucryptite.