DEVITRIFICATION BEHAVIOUR OF GLASSES IN THE BAO.4GEO(2-)PBO.4GEO(2) COMPOSITION RANGE

The devitrification behaviour of ternary tetragermanate glasses contai ning Ba2+ and Pb2+ ions in 3/1, 1/1 and 1/3 molar ratios, examined by differential thermal analysis, Fourier transform infrared spectroscopy and x-ray diffraction, is reported and discussed. Glasses with 3/1 an d 1/1 Ba2+/Pb2+ molar ratio are phase separated and devitrify in two s teps. Bulk crystallisation of BaGE(4)O(9) is followed at higher temper atures by GeO2 crystal growth on the surface of the samples. In glasse s with 1/3 Ba2+/Pb2+ molar ratio a solid solution of BaGe4O9 and of Pb Ge4O9 crystallises in a single stage.