Features of the relaxation in hyperquenched inorganic glasses during annealing

ISSN： 0031-9090

Source： Physics and Chemistry of Glasses - European Journal of Glass Science and Technology Part B, Vol.46, Iss.4, 2005-08, pp. : 354-358

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Abstract

Enthalpy relaxation of hyperquenched phosphate and silicate glasses during annealing is studied using a differential scanning calorimeter (DSC). The results show that proper annealing below the glass transition temperature (T_g) leads to a calorimetric pre-endotherm followed by an exotherm below the T_g endotherm. The pre-endotherm and the exotherm are distinguished by a crossover temperature (T_cross). With an increase in annealing temperature and time, the endotherm becomes more pronounced, whereas the exotherm gradually disappears. Hyperquenching and annealing are a requisite for the appearance of the pre-endotherm. The extent of the pre-endotherm depends on the annealing conditions. The pre-endotherm shows recovery behaviour under certain annealing and DSC-scanning conditions. The origin of the pre-endotherm is fundamentally different from that of the glass transition endotherm.