Electronic polarizability, optical basicity and XPS spectra of Sb2O3–B2O3 glasses

The average electronic polarizability of the oxide ion (αO2−) and optical basicity (Λ) of Sb2O3–B2O3 glasses have been estimated from the values of refractive index and optical band gap, and the O1s and Sb3d binding energies have been measured from X-ray photoelectron spectroscopy (XPS) spectra in order to clarify the electronic structure of oxide glasses. Both αO2− and Λ increase with increasing Sb2O3 content and conversely both O1s and Sb3d binding energies decrease. Close correlations are observed among them, and particularly it has been confirmed that the O1s binding energy is a good measure of the optical basicity of these glasses. The O1s signal in XPS spectra consists of two components: the O1s peak with higher binding energies is assigned to B–O–B bonds and that with lower binding energies corresponds to Sb–O–B and Sb–O–Sb bonds. It has been also suggested that a substantial rearrangement in the bridging oxygen bonding takes place at about 40 mol% Sb2O3: with a decrease in the number of B–O–B bonds and an increase in the number of Sb–O–B and Sb–O–Sb bonds. The covalency of Sb–O bonds increases with increasing Sb2O3 content, and its origin has been discussed in view of the good correlation between O1s and Sb3d binding energies, suggesting the formation of Sb–O bonds rich in p-character due to the increased probability of back donation of electron density from O2− to Sb3+ ions.