RAMAN-SPECTRA OF MO-TEO2 (M=MG, SR, BA AND ZN) GLASSES

The structure of MO-TeO2 (M = Mg, Sr, Ba and Zn) glasses was investigated by Raman spectroscopy. The glasses with low BaO have a continuous network constructed by sharing corners of TeO4 trigonal bipyramids and TeO3+1 polyhedra having one non-bridging oxygen (NBO) atom. In the glasses, TeO3 trigonal pyramids having NBO atoms are also formed in the continuous network. In 36BaO . 64TeO(2) glass, isolated structural fragments, such as TeO32- and Te3O(8)(4-) ions, coexist with the continuous network. The structure of MgO-TeO2 glasses is different from that of the BaO-TeO2 glasses. In glasses containing about 40 mol% MgO, a (Te3O84-)(n) unit, in which n is relatively small, is formed. The fraction of tellurium atoms forming TeO3 trigonal pyramids increases with MgO content. When MgO exceeds 40 mol%, isolated structural units, such as TeO32- and Te3O84- ions, will be formed in glasses. The SrO-TeO2 and ZnO-TeO2 glasses have the same structure as the BaO-TeO2 and MgO-TeO2 glasses, respectively.