Some Physical Properties and Boron Coordination Number of Glasses in the System CaO-Ga₂O₃-B₂O₃

Abstract

¹¹B NMR spectra, density and refractive index were measured for the CaO-Ga₂O₃-B₂O₃ glasses and interpreted in term of the structure. Distribution of the fraction, N_BO4, of boron atoms that are four-coordinated for the CaO-Ga₂O₃-B₂O₃ glasses showed roughly pattern as that for the CaO-Al₂O₃-B₂O₃ glasses. It was found that the CaO-Ga₂O₃-B₂O₃ glasses contain a considerable fraction of four-coordinated B³⁺ ions at the composition in which Ga₂O₃/CaO ratio is equal to unity, while the CaO-Al₂O₃-B₂O₃ glasses contain almost no four-coordinated B³⁺ ions at the same composition ratio, Al₂O₃/CaO=1.
Ca³⁺ ions in this glass have a coordination number of four has been shown by N_BO4 values and Raman study. Ga³⁺ ions takes the form of GaO₄^- groups with Ca²⁺ ion as a charge compensator and the form of GaO₄ groups involving one tripod oxygen.