2004 Volume 44 Issue 9 Pages 1527-1533
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/(nNa+nCa)≤0.3, where n represents the mole fraction of each cation. On the other hand, the samples having the value of nNa/(nNa+nCa)≥0.4 contain F− coordinated with both Na+ and Ca2+ and F− sixfold-coordinated by Na+.