Interionic interactions, electronic polarizability and optical basicity of oxide glasses

Abstract

Interaction parameter, A, proposed in Yamashita-Kurosawa's theory of dielectric constant, has been calculated for numerous binary oxide glasses on the basis of polarizability of oxide ion determined from refractive index. It has been established that the interaction parameter is closely related to the oxide ion polarizability and the optical basicity of the glasses. The almost linear distribution of the optical basicity obtained in the oxide glasses against the interaction parameter could be used as an optical basicity scale for the oxide glasses. It was established that the interionic interactions are strong in glasses formed by two acidic oxides and they become weaker in glasses formed by acidic and basic or two basic oxides. Generally, the interaction parameter decreases and optical basicity increases according to the sequence: phosphate, borate, silicate, germanate, tellurite, titanate glasses. It has been assumed on the basis of the known structural models and experimental results on the core level and valence band spectra of glasses that the interaction parameter represents the interionic interaction between cation and an averaged oxide ion due to overlapping of their outermost electronic orbitals to form a chemical bond. It was found that the decrease of interaction parameter correlates with small charge overlap and large cation and oxide ion polarizabilities, giving rise to an enhanced unshared oxide ion 2p electron density available for donation. The results obtained probably provide a good basis for prediction of interionic interaction in oxide glasses on the basis of refractive index.