Thermal Expansion of Substituted Copper Aluminosilicate Glasses

Abstract

The effects of various components on the thermal expansion coefficient of low‐expansion Cu2O‐Al2O3‐SiO2 glasses were examined. When a component of glass was substituted by another oxide, the expansion coefficient always increased, except for substitution of Al2O3 by B2O3. This result indicates that the essential components to maintain the low expansivity are Cu2O, such trivalent oxides as Al2O3 and B2O3, and tetravalent oxide SiO2. Glasses of the systems Cu2O‐Al2O3‐B2O3, Cu2O‐Al2O3‐GeO2, and Cu2O‐Al2O3‐P2O5, which were derived by replacing SiO2 by other network‐forming oxides, showed fairly low expansion coefficients compared with other conventional borate, germanate, and phosphate glasses. It was also found that the valence state of copper ions is important for the thermal expansion characteristics of these glasses; Cu+ ions contribute to the low expansion coefficient.