Crystallization behaviour of some TeO₂ - ZnO glasses

Zinc-tellurite glasses, comprising 80 mol% TeO₂ - 20 mol% ZnO (hereafter referred to as 0.8TeO₂ - 0.2ZnO) and 60 mol% TeO ₂ - 40 mol% ZnO (hereafter referred to as 0.6TeO₂ - 0.4ZnO), were crystallized at different temperatures on the basis of DTA analyses. Using XRD, SEM and EDS analyses, the crystallizing phases, with their shapes and sizes, were determined in these glass compositions. Thus, different effects of ZnO content on crystallization of binary zinc-tellurite glasses were studied. It was found that crystallizing phases were different for two different samples. In the 80TeO₂ - 20ZnO glasses, αx-TeO₂ (paratellurite) crystallizes first at around 428°C, and Zn ₂Te₃O₈ phase crystallizes at around 458°C. On the other hand, in the 60TeO₂ - 40ZnO glass, only the Zn ₂Te₃O₈ phase crystallizes. Since this crystallization takes place at around 432°C, it can be concluded that increasing the ZnO content in zinc-tellurite glasses slightly increases the crystallization temperature.