Thermal properties of silica. Part 2.—Thermal expansion coefficient of vitreous silica

Abstract

Vitreous silica possesses several exceptional temperature or volume-dependent properties, notably an extremely low coefficient of thermal expansion. Evidence is presented to show that this low expansion coefficient could be the resultant of two opposing, interdependent tendencies, namely, an increase in the silicon-oxygen distance as the temperature is increased and a decrease in the bond angle at the oxygen atom. The latter effect could be large enough to provide not only very low values of the expansion coefficient, but also negative expansion coefficients which are observed in the high-temperature crystalline modifications of silica.