TRANSPARENT, ESSENTIALLY COLORLESS AND NON-DIFFUSING BETA-QUARTZ GLASS-CERAMICS; ARTICLES IN SAID GLASS-CERAMICS; PRECURSOR GLASSES.

摘要

Transparent, essentially colorless and non-diffusing -quartz glass-ceramics and glass compositions for forming the same have a composition, free of arsenic oxide, antimony oxide and rare earth oxides except for inevitable trace amounts, which contains, expressed as percentages by weight of oxides 62-72% of SiO2, 20-23% of Al2O3, 2.8-5% of Li2O, 0.1-0.6% of SnO2, 1.9-4% of TiO2, 1.6-3% of ZrO2, less than 0.4% of MgO, 2.5-6% of ZnO and/or BaO and/or SrO, less than 250 ppm of Fe2O3; and their crystallites present in the -quartz solid solution have an average size of less than 35 nm. The glass-ceramics exhibit low thermal expansion and are easily obtained at an industrial scale.