Thermal Expansion of Some Simple Glasses

Abstract

In order to obtain a better understanding of the contribution of various oxides to the thermal expansion of silicate glasses, a number of glasses of widely different compositions were examined. In contrast with the viscosity, the thermal expansion in the range 25° to 150°C. is not materially affected in glasses containing more than 67 mole % SiO2 if a noble-gas-type cation * is replaced by a non-noble-gas-type cation † of the same size and charge. In such high-silica glasses, the substitution of a noble-gas-type cation of a larger size for a similar cation of a smaller size increases the coefficient of expansion. The increased expansion, which is noticeable in glasses above the transition range, and the difference in the expansion characteristics of the chilled and annealed glasses gradually diminish as the basicity of the glass increases.