Electronic polarizability, optical basicity, and interaction parameter of La₂O₃ and related glasses

The electronic polarizability and optical basicity of La₂O₃ and related glasses have been determined from ultraviolet absorption spectra and calculations based on the Lorentz-Lorenz equation. The optical basicity for La₂O₃ oxide is found to be 1.07, being much larger compared with typical glass-forming oxides such as B₂O₃ (0.42) and SiO₂ (0.48) but being similar to heavy element oxides such as TeO₂ (0.93). The Yamashita and Kurosawa's interaction parameter of La₂O₃ is 0.03 Å^-3, indicating that La₂O₃ is classified as a normal ionic (basic) oxide, i.e., an ionic bonding character in the La³⁺-O bond is proposed. Close correlations are confirmed among optical basicity, interaction parameter, and oxygen 1s binding energy in x-ray photoelectron (XPS) spectra for La₂O₃-P₂O₅ and other La₂O₃-containing glasses. It is found from XPS and Raman spectra that La³⁺ ions in La₂O₃-P₂O₅ glasses act as network modifiers, supporting an ionic bonding character in the La³⁺-O bond. The parameters related to electronic polarizability in La₂O₃ determined in the present study would be useful for the design of rare-earth containing optical functional glasses.