Chapter 12: RO–M₂O₃–GeO₂ Glasses Check Access

The CaO–Al₂O₃–GeO₂ and BaO–Ga₂O₃–GeO₂ systems are the only RO–M₂O₃–GeO₂ systems which have been studied in detail. Limited data are also available for glasses in the CaO–Ga₂O₃–GeO₂, PbO–Al₂O₃–GeO₂, PbO–Ga₂O₃–GeO₂, and BaO–La₂O₃–GeO₂ systems. The maxima in density and refractive index gradually decrease in magnitude as Al₂O₃ replaces GeO₂ for glasses with a constant CaO/Al₂O₃ ratio, i.e. the germanate anomalies are reduced by increasing the CaO/Al₂O₃ ratio. There are no maxima in the glass transformation temperature, i.e. no germanate anomalies, for any of the glasses lying on lines of constant CaO/Al₂O₃ ratio. The barium gallogermanate glasses do not exhibit germanate anomalies in any of their properties. Data for the calcium gallogermanate glasses are limited to glasses containing an equimolar ratio of CaO to Ga₂O₃. The densities of these glasses exhibit a small maximum, but the other properties exhibit rather complex behavior which cannot be explained at this time. Data for the other RO–M₂O₃–GeO₂ glasses are very limited. The densities and refractive indices of these glasses increase with increasing RO concentration. The glass transformation temperature of glasses containing PbO decreases as the PbO content increases.