Calcium fluoroaluminate glasses

Abstract

Binary calcium aluminate glasses containing 59–70 mol % CaO have been formed, as have a series of glasses in which CaF2 replaces CaO. The transformation range viscosity and glass transformation temperature of the binary glasses decreases as the CaO concentration increases, whereas the thermal expansion coefficient, refractive index, and infrared cutoff wavelength increase. The substitution of CaF2 for CaO results in a decrease in the refractive index, viscosity, and glass transformation temperature, an increase in the thermal expansion coefficient and electrical conductivity, and no detectable change in the infrared cutoff wavelength. Magic angle spinning nuclear magnetic resonance indicates that the aluminum ions in these glasses are in tetrahedral coordination. These results will be discussed in terms of the structures of these glasses.