Low expansing transparent crystallized glass-ceramic.

摘要

A low expansion crystallized glass-ceramic which has a coefficient of thermal expansion ( alpha x 10<-><7> / DEG C) within the range of from - 10 to + 10, has a remarkably reduced variation in the coefficient of thermal expansion accompanied by variation in heat treatment conditions, has an excellent optical homogeniety owing to reduced melting temperature in the base glass and has an improved transparency is obtained by restricting the ratio in weight of Al2O3 to (SiO2 + P2O5) within the range of 0.38 and 0.50 and adding MgO, BaO and ZnO of specific content ranges as essential ingredients in a base glass of a SiO2 - Al2O3 - Li2O system containing P2 O5 as an optional ingredient and TiO2 and ZrO2 as nucleating agents.