Thermodynamic properties of (TeO2) n (WO3)1 − n glasses in the range 0–650 K

Abstract

The heat capacity of (TeO2) n (WO3)1 − n tellurite glasses with n = 0.75, 0.78, 0.85, and 0.90 has been determined using precision adiabatic calorimetry (6–350 K) and dynamic scanning calorimetry (320–650 K), and the thermodynamic characteristics of their glassy state and devitrification have been evaluated. The experimental heat capacity data have been used to calculate the standard thermodynamic functions of the glassy and supercooled liquid states at temperatures from T → 0 to 650 K: heat capacity C p 0 (T), enthalpy H 0(T) — H 0(0), entropy S 0(T), and Gibbs function G 0(T) — H 0(0). The character of structural heterodynamicity of the tellurite glasses has been assessed by processing the low-temperature heat capacity data using the multifractal formulation of the Debye theory of heat capacity of solids. The composition dependences of the devitrification temperature and 298.15-K thermodynamic functions have been obtained, and the 298.15-K C p 0 of tellurium dioxide has been estimated. The thermal and thermodynamic properties of the (TeO2) n (WO3)1 − n tellurite glasses have been compared with those of (TeO2) n (ZnO)1 − n glasses.