On the structure of molybdate–tellurite glasses

Abstract

A model of continuous network of molybdate–tellurite (MoO3–TeO2) glasses is developed on the basis of quantum-chemical modeling. The model allows one to relate the glass structure and vibrational properties (in particular, the vibrational frequency, Raman band intensity, and polarization) with glass composition. The continuous molybdate–tellurite glass network is shown to be formed mainly by structural units of four types, TeO4 trigonal bipyramids, OTeO2 trigonal pyramids, OMoO5 single octahedra and 2[OMoO5] paired octahedra. No structural units of any other type are necessary to build the continuous network. Interpretation of the Raman spectra of molybdate–tellurite glasses in the 550–950 cm−1 range is suggested. In particular, a strongly polarized Raman band with the maximum in the range of 920–940 cm−1 characteristic for these glasses turns out to be caused for the most part by stretching vibrations of MoO double bonds in single, OMoO5, and paired, 2[OMoO5], molybdate octahedra, the ratio of single and paired molybdate octahedra concentrations growing almost linearly from ≈0.4 to ≈0.5 with MoO3 content increasing overall the glass formation region (from 10 up to 60 mol%). The model can be applied to analyze the vibrational spectra of molybdate–tellurite glasses of various compositions.