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

Glass formation and structure are investigated in binary tellurite sys tems containing YO3/2, InO3/2, LaO3/2, ZrO2, SnO2, HfO2, and ThO2 as s econd components. No glasses are obtained in two systems, ZrO2-TeO2 an d SnO2-TeO2, because of the precipitation of ZrTe3O8 and SnTe3O8 cryst als. Raman spectra and glass properties, such as transition temperatur e, thermal expansion and density, were measured. Glasses having low La O3/2 content have a continuous network structure composed of corner-sh aring TeO4 trigonal bipyramids and TeO3+1 polyhedra having one non-bri dging oxygen atom. Further increase of LaO3/2 content accelerates a co nversion of TeO4 trigonal bipyramids and TeO3+1 polyhedra into TeO3 tr igonal pyramids having two or three non-bridging oxygen atoms. In the YO3/2-TeO2 and ThO2-TeO2 systems, the change of glass structure follow s the same process as in LaO3/2-TeO2 glasses. In 23InO(3/2) . 77TeO(2) glass, few structural fragments composed of TeO3 trigonal pyramids ar e formed. There is a possibility that 5HfO(2) . 95TeO(2) glass contain s a small fraction of structural fragments present in HfTe3O8 crystal.