Electronic polarizability and its temperature dependence of Bi2O3–B2O3 glasses

The refractive index (n) and density (p) of xBi 2 O 3 -(100-x)B 2 O 3 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 (α O2- ) and optical basicity (Λ). It is found that the values of n, α O2- , and Λ increase almost linearly with increasing temperature. The value of the temperature dependence of refractive index, dn/dT, increases with increasing Bi 2 0 3 content. Contrary, the values of dα O2 - /dT, and dΛ/dT, tend to decrease with increasing Bi 2 O 3 content. It is suggested that the temperature dependence of the electronic polarizability of oxide ions in xBi 2 O 3 -(100-x)B 2 O 3 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 α O2- and A in the present glass system might be related to the extremely weak single bond strength of Bi 2 0 3 compared with the strong single bond strength of B 2 O 3 .