Viscosity and refractive index of M2O-TeO2(M = Li, Na and K) melts

Abstract

We measured the viscosity and the refractive index of the binary tellurite glasses and melts, (M2O-TeO2 M = Li, Na and K), and investigated the thermal and compositional dependences of the properties. It was found that the viscosity and the refractive index of the binary tellurite melts decreased with increasing temperature, M2O content, and the radius of added cation. It was attributed to the structural change of melt from TeO4 trigonal bipyramid to TeO4- trigonal bipyramid and TeO3 trigonal pyramid with increasing temperature and M2O content. In an attempt to determine the change of tellurite structural units (TeO4, TeO4- and TeO3) with temperature and M2O content, the fraction of structural units in the melts was calculated from the refractive index of melts on the basis of the relationship between the refractive index and the structural units of tellurite glasses. It was found that the fraction of TeO3 increased with increasing temperature and M2O content, which was corresponded to the thermal and compositional dependences of the viscosity and refractive index measurements.© 2010 the Japan Institute of Metals.