Electronic polarizability and its temperature dependence of Bi2O3–B2O3 glasses

The refractive index (n) and density (ρ) of xBi2O3–(100 − x)B2O3 glasses with x = 32.5–60 (mol%) are measured in the temperature range of 30–150 °C in order to clarify the temperature dependence of the electronic polarizability of oxide ions (αO2−) and optical basicity (Λ). It is found that the values of n, αO2−, and Λ increase almost linearly with increasing temperature. The value of the temperature dependence of refractive index, dn/dT, increases with increasing Bi2O3 content. Contrary, the values of dαO2−/dT, and dΛ/dT, tend to decrease with increasing Bi2O3 content. It is suggested that the temperature dependence of the electronic polarizability of oxide ions in xBi2O3–(100 − x)B2O3 glasses has a large contribution for the temperature dependence of the refractive index in comparison with the contribution of the volume thermal expansion coefficient. The features in the temperature dependence of αO2− and Λ in the present glass system might be related to the extremely weak single bond strength of Bi2O3 compared with the strong single bond strength of B2O3.