Crystallization Behaviour of some TeO2-ZnO Glasses

Zinc-tellurite glasses, comprising 80 mol% TeO2-20 mol% ZnO and 60 mol% TeO2-40 mol% ZnO were crystallised at different temperatures on the basis of DTA analyses. Using XRD, SEM and EDS analyses, the crystallising phases, and their shapes and sizes, were determined in these glass compositions. Thus, different effects of ZnO content on crystallisation of binary zinc-tellurite glasses were studied. It was found that crystallising phases were different for two different samples. In the 80TeO2-20ZnO glasses, alpha-TeO2 (paratellurite) crystallises first at around 428 C, and Zn2Te3O8 phase crystallises at around 458 C. In the 60TeO2-40ZnO glass, only the Zn2Te3O8 phase crystallises. Since this crystallisation takes place at around 432 C, it can be concluded that increasing the ZnO content in zinc-tellurite glasses slightly increases the crystallisation temperature. 4 refs.