Thermodynamic Properties of (TeO2)0.95-n-z(ZnO)z(Na2O)n(Bi2O3)0.05 Glasses

The heat capacity (C-p(0)) of the tellurite glasses (TeO2)(0.70)(ZnO)(0.15)(Na2O)(0.10)(Bi2O3)(0.05) (I), (TeO2)(0.75)(ZnO)(0.10)(Na2O)(0.10)(Bi2O3)(0.05) (II), and (TeO2)(0.75)(ZnO)(0.15)(Na2O)(0.05)(Bi2O3)(0.05) (III) has been measured in the temperature range 255-750 K using a differential scanning calorimeter (glasses I-III) and in the range 208-325 K using an adiabatic calorimeter (glass II). We have determined the temperature ranges of the glass transition, evaluated the thermodynamic characteristics of the glass transition and glassy state, and estimated the crystallization onset temperatures. Using the experimental data and a statistical model approach, we have calculated the standard thermodynamic functions for glassy and "supercooled liquid" states in the temperature range 0-740 K: heat capacity C-p(0)(T), enthalpy H-0(T) - H-0(0), entropy S-0(T) - S-0(0), and Gibbs function G(0)(T)- G(0)(0).