Structure and properties of ZnO–B 2O 3–P 2O 5–TeO 2 glasses

Abstract

Zinc borophosphate glasses doped with TeO 2 were studied in the compositional series (100 − x)[0.5ZnO–0.1B 2O 3–0.4P 2O 5]– xTeO 2 in a broad concentration range of x = 0–80 mol% TeO 2. The structure of the glasses was studied by Raman and IR spectroscopy and by 31P and 11B MAS NMR spectroscopy. According to the Raman and IR spectra, TeO 2 is incorporated in the structural network in the form of TeO 3, TeO 3+1 and TeO 4 structural units. The ratio of TeO 4/TeO 3 increases with increasing TeO 2 content in the glasses. The incorporation of TeO x units into the glass network is associated with the depolymerisation of phosphate chains, as revealed by Raman spectroscopy. The incorporation of TeO 2 modifies also the coordination of boron atoms, where B(OP) 4 structural units are gradually replaced by B(OP) 4− n (OTe) n units. The addition of TeO 2 to the parent zinc borophosphate glass results in a decrease of glass transition temperature associated with the replacement of stronger P–O and B–O bonds by weaker Te–O bonds. Chemical durability of glasses reveals a minimum at the glass containing 10 mol% TeO 2, but with further additions of TeO 2 it improves and the glasses with a high TeO 2 content reveal better durability than the parent zinc borophosphate glass.