Glass ceramic

Abstract

The invention relates to a glass and a glass-ceramic comprising beta-quartz and/or keatite solid solutions, and to a process for their production, and to their use as substrate material for coating. Glass-ceramic comprising beta-quartz and/or keatite solid solutions with a surface roughness without polishing of Ra<50 nm, a thermal expansion in the temperature range between 20° C. and 300° C. of <1.2•10−6/K, a transmission in the near infrared region at 1050 nm of >85% for a 4 mm thickness, and a composition in % by weight, based on the total composition, containing: Li2O 3.0-5.5 Na2O 0-2.5 K2O 0-2.0 Σ Na2O + K2O 0.5-3.0 Σ MgO + ZnO <0.3 SrO 0-2.0 BaO 0-3.5 B2O3 0-4.0 Al2O3 19.0-27.0 SiO2 55.0-66.0 TiO2 1.0-5.5 ZrO2 0-2.5 Σ TiO2 + ZrO2 3.0-6.0 P2O5 0-8.0 Fe2O3 <200 ppm F 0-0.6 as substitute for O and, if appropriate, at least one refining agent, such as As2O3, Sb2O3, SnO2, CeO2, sulphate and chloride compounds.

Dependencies are inferred from the claim text.