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)Ba O. (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 t he heat treatments performed near the glass transition temperature and thei r effect on the devitrification behaviour have been examined by Fourier tra nsform infrared spectroscopy, differential thermal analysis and x-ray diffr action. The 16 h heat treatment produces a microphase separation in the gla ssy 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.