Glass formation and structural studies of glasses in the TeO2 - ZnO - Bi2O3 - Nb2O5 system

In this study we determined the glass formation region in the TeO2 - ZnO - Bi2O3 - Nb2O5 system. The investigation covers TeO2 - based glasses containing ZnO (from 10 to 40 mol%), Bi2O3 (6-10 mol%) and Nb2O5 (6-10 mol%). The glasses obtained were transparent and yellow in colour. The thermal stability of the samples determined by DTA was found to be about 100 degrees C. Some physical characteristics (density, molar volume, oxygen molar volume and oxygen packing density) were estimated as well. The analysis of IR spectra showed that the network of glasses consists mainly of TeO4 (tbp) units, while Raman spectroscopy revealed the existence of TeO4 (tbp), TeO3+1 and TeO3 (tp) units. The UV-Vis spectroscopy established a red shifting of the cut-off depending on composition and the glass rich in TeO2 exhibited cut-off at about 388 nm while that with low TeO2 content was 378 nm.