RAMAN-SPECTRA OF BINARY TELLURITE GLASSES CONTAINING TRI-VALENT OR TETRA-VALENT CATIONS

Glass formation and structure are investigated in binary tellurite systems containing YO3/2, InO3/2, LaO3/2, ZrO2, SnO2, HfO2, and ThO2 as second components. No glasses are obtained in two systems, ZrO2-TeO2 and SnO2-TeO2, because of the precipitation of ZrTe3O8 and SnTe3O8 crystals. Raman spectra and glass properties, such as transition temperature, thermal expansion and density, were measured. Glasses having low LaO3/2 content have a continuous network structure composed of corner-sharing TeO4 trigonal bipyramids and TeO3+1 polyhedra having one non-bridging oxygen atom. Further increase of LaO3/2 content accelerates a conversion of TeO4 trigonal bipyramids and TeO3+1 polyhedra into TeO3 trigonal pyramids having two or three non-bridging oxygen atoms. In the YO3/2-TeO2 and ThO2-TeO2 systems, the change of glass structure follows the same process as in LaO3/2-TeO2 glasses. In 23InO(3/2) . 77TeO(2) glass, few structural fragments composed of TeO3 trigonal pyramids are formed. There is a possibility that 5HfO(2) . 95TeO(2) glass contains a small fraction of structural fragments present in HfTe3O8 crystal.