GLASS-TRANSITION TEMPERATURE AND DEVITRIFICATION BEHAVIOR OF LITHIUM-TITANIUM-GERMANATE GLASSES

The effect of replacing GeO2 by TiO2 on the glass-transition temperatu re and devitrification behaviour in lithium tetragermanate glass has b een studied by differential thermal analysis, and Fourier-transform in frared spectra. The glass compositions are expressed by the general fo rmula Li2OxTiO2(4-x)GeO2 with 0.00 less than or equal to x less than o r equal to 1.00. The anion network of all glasses was found to contain GeO4 and GeO6 groups in the same molar ratio. The grass-transition an d crystallisation temperature values are both increased by the progres sive replacement of GeO2 by TiO2. Glasses with x < 0.5 devitrify into lithium tetragermanate crystals. Glasses with x greater than or equal to 0.5 devitrify in two steps into two non-identifiable phases. The in fluence on the crystallisation mechanisms of the specific surface of t he samples was also pointed out. (C) 1997 Elsevier Science B.V.