Thermal properties and stability of TeO2 containing phosphate glasses

Abstract: Differential thermal analysis and thermodilatometry have been used to study the thermal behaviour of glasses in the ZnO–P2O5–TeO2 system prepared in compositional series (100− x)[0.5ZnO–0.5P2O5]–xTeO2 (X-series) and 50ZnO–(50− y)P2O5–yTeO2 (Y-series) within the concentration range of x =0–60 and y =0–40mol% TeO2. The addition of TeO2 to the starting zinc metaphosphate glass resulted in a gradual increase of thermal expansion coefficient from 12.2 up to 16.6ppm°C−1, whereas glass transition temperature and dilatometric softening temperature reveal a minimum at the glass with x =30mol% and y =10mol% TeO2. All glasses crystallize on heating within the temperature range ∼500–700°C. The contribution of the surface crystallization mechanism over the internal one increases with increasing TeO2 content. Major compounds formed by crystallization were Zn(PO3)2 and Zn2P2O7. [Copyright &y& Elsevier]