The kinetics of enthalpy relaxation (recovery) at the glass transition in xK2O·(20 - x)MgO·80TeO2 glasses has been examined from heat capacity measurements using differential scanning calorimetry to clarify the features of the structural relaxation in ternary TeO2-based glasses. Ternary glasses such as 10K2O·10MgO·80TeO2 show high thermal resistance against crystallization compared with binary glasses. The degree of fragility m estimated from the activation energy for viscous flow Eη and the glass transition temperature Tg is m = 55-62, indicating a fragile character in TeO2-based glasses. Large heat capacity changes of 43.1-48.2 J·mol-1·K-1 are also observed at the glass transition. The activation energy for enthalpy relaxation ΔH is evaluated from the cooling rate dependence of the limiting fictive temperature, and values of ΔH = 897-1268 kJ·mol-1 are obtained. Negative deviation from additivity in ΔH is also observed. Values of the Kovacs-Aklonis-Huchinson-Ramos (KAHR) parameter θ estimated from ΔH and Tg are 0.33-0.42 K-1. It has been proposed that ternary glasses have more homogeneous and constrained glass structure compared with binary glasses.
|Number of pages||7|
|Journal||Journal of the American Ceramic Society|
|Publication status||Published - 2000|
ASJC Scopus subject areas
- Ceramics and Composites
- Materials Chemistry