On the Possibility of Precision Control of the Linear Thermal Expansion Coefficient of Transparent Lithium-Aluminum- Silicate Sitals Near Zero Values

It is shown that the linear thermal expansion coefficient (CLTE) for sitalls based on the lithium aluminosilicate system can be precisely controlled near values close to zero in the temperature range from –80 to +500°C. It was found that heat-treatment for several hours at temperatures corresponding to the stage of nucleation of a crystalline phase makes it possible, after a lengthy incubation period, to change the sign of the CLTE of sitall from positive to negative, while preserving its sign constancy in the entire temperature interval near zero values of the CLTE.