Influence of barium oxide on glass-forming ability and glass stability of the tellurite-phosphate oxide glasses: Thermal and structural investigations

The effect of BaO content on the glass-forming ability, glass stability and structure of tellurite-phosphate oxide glasses in the 70TeO(2)-10P(2)O(5)-(20-x)ZnO-xBaO (x=0, 5 and 10 mol%) system has been discussed. From the differential scanning calorimetry, the glass transition (Tg), crystallization (Tc) and the melting (Tm) temperatures were estimated. The decrease in reduced glass transition temperature (Tr-g) and glass-forming tendency parameter (K-h(Tc-1)) with addition and increasing BaO caused a decrease in the glass-forming ability of glasses. It was also found that the thermal stability of these glasses against crystallization decreased with increase in BaO concentration into chemical composition of base glass, i.e., glass without barium oxide. The FTIR spectra were measured to understand the structure of the obtained tellurite-phosphate oxide glasses. The results have shown that phosphorous and tellurium ions were taken part in the formation of the glass network of the studied glasses. The addition of BaO caused significant changes in the FTIR spectra of glasses. More and more TeO3 and TeO3+delta units and PO 42- groups (Q(1) units) were created when the BaO was added into the chemical composition of the base glass. Increasing barium ions content into the chemical composition of glasses caused depolymerization of the tellurite-phosphate oxide glass network.