The non-isothermal devitrification of glasses in the CaO center dot 4GeO(2)-BaO center dot 4GeO(2) composition range

The effect of replacing CaO by BaO on the glass transition temperature and on devitrification behaviour in a series of glasses in the calcium tetrager manate-barium tetragermanate composition range has been studied by differen tial thermal analysis (DTA), X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectra. A similar GeO4/GeO6 molar ratio was found in all t he glasses of the series. The progressive replacement of CaO by BaO caused a decrease in the glass transition temperature. All the glasses studied exh ibited internal crystal nucleation. The crystallizing phases were identifie d as CaGe4O9 and BaGe4O9. No solid solutions occurred in the glass containi ng both CaO and BaO. The effect of the specific surface of the glass sample s on devitrification processes has also been studied. (C) 2000 Elsevier Sci ence B.V. All rights reserved.