Influence of TiO2 on the thermal stability and crystallization of glasses within TeO2 - Bi2O3 - Nb2O5 - ZnO system

In this study we selected the TeO2 - Bi2O3 - Nb2O5 - ZnO system. The investigation covers TeO2 - based glasses containing Nb2O5 and Bi2O3 up to 10 mol%, ZnO from 5 to 10 mol%, while the TiO2 varies from 5 to 50 mol%. The obtained glasses were transparent and yellow colored (TiO2 up to 20 mol%). The thermal stability of the samples was determined by DTA using the difference Delta T between exothermic peak of crystallization (T-x) and that for glass transition temperature Tg (Delta T = 50-115 degrees C). Several crystalline phases were identified by XRD, between them more important are ZnTeO3 and TiTe3O8 (in compositions above 20 mol% TiO2) due to their good dielectric properties. The analysis of spectra shows that network of glasses consist mainly of TeO4 (TBP) units. The preliminary electrical measurements showed that the samples are with low conductivity and there is no significant change of the dielectric losses up to 600 degrees C. The as-prepared crystalline samples are with low conductivity and good dielectric properties.