US Patent 7144835 Aluminum-free borosilicate glass and applications thereof

The aluminum-free borosilicate glass has a composition in percent by weight based on oxide content of: SiO2, 65–77; B2O3, 7–20; Li2O, 0–2; Na2O, 0–4; K2O, 3–12; MgO, 0–2; CaO, 0–2; with MgO+CaO, 0–3; BaO, 0–3; ZnO, 0–2; ZrO2, 0.8–12; TiO2, 0–10; CeO2, 0–1; and F−, 0–0.6. This glass advantageously has a coefficient of thermal expansion α (20° C.; 300° C.) of between 3.0×10−6/K and 6×10−6/K, good chemical resistance and a working point VA of between 990° C. and 1290° C.