Formation and Properties of Calcia-Calcium Fluoride-Alumina Glasses

The glass formation region has been determined for the CaO-CaF₂-Al₂O₃ ternary system. The glass transformation temperature of these glasses decreases as the CaF₂ concentration increases, whereas the thermal expansion coefficient and electrical conductivity increase. MAS-NMR (magic-angle-spinning nuclear magnetic resonance) indicates that the aluminum ions in these glasses are in tetrahedral coordination. The structures of these glasses are proposed to be analogous to those of similar silicate glasses, with aluminum ions replacing silicon ions and fluorine acting as a nonbridging anion.