Radiation effects on thermal expansion of some ternary alkali-silicate glasses

Abstract

The thermal expansion of some ternary silicate glasses was measured from room temperature to above the softening temperature. The expansion curves for all the glasses showed similar behaviour. Increasing barium or zinc oxide content decreased the thermal coefficient of expansion of glass. Gamma irradiation caused a remarkable decrease in thermal expansion. Several mechanisms of thermal expansion were advanced and the experimental results are explained by considering the bond strengths, ionic sizes of the cations and irradiation damage. The increase in thermal expansion of some oxides can be attributed to the increase in polarizability of the O 2− ions in the glass, the mutual interaction of the ions present, and the possible effects of compaction. The values of glass transformation temperature and softening temperature, T g and T s, respectively, are assumed to depend to a large extent on the entropy changes during heating as well as on the concentration of the defects caused by irradiation.