STRUCTURAL DEVELOPMENTS IN SUPERCOOLED ALKALI TELLURITE MELTS

Brillouin light scattering has been used to determine the high-frequen cy complex mechanical modulus of alkali tellurite liquids and glasses, as a function of the temperature. In order to adequately describe the temperature dependence of this modulus, a modified Maxwell model for linear viscoelastic systems was developed. Accordingly, the modulus co mprises relaxational components and a temperature-dependent static mod ulus, the magnitudes of which are determined by the equilibrium volume fraction of kinetically arrested domains. In binary alkali tellurites the structure degrades with increasing temperature by means of the di ssolution of network rings, which involves the conversion of TeO4 trig onal bipyramids into TeO3 trigonal pyramids. This decrease.in network connectivity is believed to be responsible for the decrease in the ela stic modulus and to cause the release of structural components into a viscoelastic state. At high-temperatures structural dynamics can be de scribed with a single relaxation lime. [S0163-1829(98)05326-0].