Glass transition temperature and devitrification behaviour of lithium-titanium-germanate glasses

Abstract

The effect of replacing GeO 2 by TiO 2 on the glass-transition temperature and devitrification behaviour in lithium tetragermanate glass has been studied by differential thermal analysis, and Fourier- transform infrared spectra. The glass compositions are expressed by the general formula Li 2O xTiO 2(4− x)GeO 2 with 0.00 ≤ x ≤ 1.00. The anion network of all glasses was found to contain GeO 4 and GeO 6 groups in the same molar ratio. The glass-transition and crystallisation temperature values are both increased by the progressive replacement of GeO 2 by TiO 2. Glasses with x < 0.5 devitrify into lithium tetragermanate crystals. Glasses with x ≥ 0.5 devitrify in two steps into two non-identifiable phases. The influence on the crystallisation mechanisms of the specific surface of the samples was also pointed out.