STRUCTURE AND NONISOTHERMAL CRYSTALLIZATION OF GLASSES IN THE BAO-B2O3-TIO2 SYSTEM

The structure and devitrification behaviour of barium borotitanate gla sses examined by Fourier transform infrared spectroscopy, differential thermal analysis and x-ray diffraction, are reported. Glass compositi ons are expressed by the formula: (50-x/2)BaO.(50-x/2)B2O3.xTiO(2) wit h x=4, 8 and 16. Titanium acting as glassformer gives a more polymeris ed structure increasing the glass stability with respect to devitrific ation. The nonisothermal devitrification of the studied glasses occurs in one or two steps depending on the TiO2 content in the glass compos ition and the specific surface area of the sample. The surface crystal lisation was found to be dominant for all glasses. The investigated gl asses devitrify forming beta-BaB2O4 microcrystals as the main crystall ine phase.