Structure and properties of glasses in ZnO–P 2O 5–TeO 2 system

Abstract

Glasses in the ternary ZnO–P 2O 5–TeO 2 system were prepared and studied in two compositional series (100 − x)[0.5ZnO–0.5P 2O 5]–xTeO 2 (X-series) and 50ZnO–(50 − y)P 2O 5–yTeO 2 (Y-series) within the concentration range of x = 0–60 and y = 0–40 mol% TeO 2. Their structure was studied by Raman and 31P MAS NMR spectroscopies. The incorporation of TeO x units into the structural network is associated with the depolymerisation of phosphate chain structure as revealed by both methods. At a high TeO 2 content isolated PO 4 tetrahedra are formed in the structure of glass series Y, while diphosphate O 3P–O–PO 3 groups are present in the structure of the glass series X. In the structure of glass series Y tellurium atoms form predominantly TeO 3 trigonal pyramids, whereas in the X glass series TeO 4 trigonal bipyramids prevail in the glass structure. The addition of TeO 2 to the parent zinc metaphosphate glass results in a decrease of glass transition temperature in both compositional series associated with the replacement of stronger P―O bonds by weaker Te―O bonds.