FTIR and DTA study of structural transformations and crystallisation in BaO-B2O3-TiO2 glasses

Glasses whose compositions are expressed by the general formula. (50-x/2)BaO. (50-x/2)B(2)O(3 .)xTiO(2) with x=4, 8 and 16 have been prepared and the structural modifications occurring in the glass network as consequence of the heat treatments performed near the glass transition temperature and their effect on the devitrification behaviour have been examined by Fourier transform infrared spectroscopy, differential thermal analysis and x-ray diffraction. The 16 h heat treatment produces a microphase separation in the glassy matrix of all investigated glasses with a typical 'droplet structure'. Furthermore, for the glass with x=16, during this hear treatment nucleation of BaB4O7 crystals occurs. These crystals, for long nucleation times, act as heterogeneous nuclei for the growth of beta-BaB2O4 crystals.