Density and thermal expansion measurements of several mixed oxide glasses in the solid and liquid regions

Abstract

The density and thermal expansion of a number of mixed oxide glasses were measured in the solid and liquid regions by gamma densitometry. With this non-contacting technique, both physical regimes may be investigated as the temperature is varied and the glass viscosity varies over a wide range. Where rate-dependent crystallization can occur, the technique allows the continuous measurement of density as the liquid cools to a supercooled glass or a crystalline solid. Lead borate glasses were investigated in the range from 27 to 42 mol % PbO. The liquid phase volumetric thermal expansion coefficient was observed to decrease with increasing PbO content, in contrast to the solid phase linear thermal expansion coefficient. In soda-baria phosphate glasses (50 mol % P/sub 2/O/sub 5/), liquid phase volumetric expansion coefficients were found to vary as the solid phase linear expansion coefficients. Two soda-alumina silicate glasses (60 mol % SiO/sub 2/) were investigated as well. Measurements on a lithia-aluminosilicate glass ceramic were obtained by this method to approximately 400/sup 0/C above the limit of conventional dilatometry, thereby allowing the measurement of the thermal expansion of high temperature crystalline phases, as well as the liquid phase density.