Ceramics-Silikáty 57 (1) 66-73 (2013)

THERMODYNAMIC MODEL AND VISCOSITY OF SELECTED ZIRCONIA CONTAINING SILICATE GLASSES

The compositional dependence of viscosity, and viscous flow activation energy of glasses with composition xNa₂O∙(15-x) K₂O∙yCaO∙(10-y)ZnO∙zZrO₂∙(75-z)SiO₂ (x = 0, 7.5, 15; y = 0, 5, 10; z = 0, 1, 3, 5, 7) was analyzed. The studied glasses were described by the thermodynamic model of Shakhmatkin and Vedishcheva considering the glass as an equilibrium ideal solution of species with stoichiometry given by the composition of stable crystalline phases of respective glass forming system. Viscosity-composition relationships were described by the regression approach considering the viscous flow activation energy and the particular isokome temperature as multilinear function of equilibrium molar amounts of system components. The classical approach where the mole fractions of individual oxides are considered as independent variables was compared with the thermodynamic model. On the basis of statistical analysis there was proved that the thermodynamic model is able to describe the composition property relationships with higher reliability. Moreover, due its better physical justification, thermodynamic model can be even used for predictive purposes.

Keywords: Zirconia-silicate glasses, Thermodynamic model, Viscosity, Property-composition relationships