Coordination Environment of Fluorine in the CaO-SiO2-CaF 2 Glasses Bearing Na2O: A Solid-state 19F MAS NMR Study

Abstract

The coordination environment of fluorine in the CaO-SiO2- CaF2-Na2O glasses has been measured by 19F MAS NMR over a wide composition range including the similar compositions to those of mould fluxes so as to determine the composition dependence of the coordination environment of F-. Most of F- are fourfold-coordinated by Ca2+ for the samples having the value of nNa/(n Na + nCa)≤0.3, where n represents the mole fraction of each cation. On the other hand, the samples having the value of n Na/(nNa + nCa)≥0.4 contain F- coordinated with both Na+ and Ca2+ and F- sixfold-coordinated by Na+.