CALORIMETRIC STUDIES OF STRUCTURAL RELAXATION IN AGI-AGPO3 GLASSES

Differential scanning calorimetry data of AgPO3 and AgI-AgPO3 glasses have been described in terms of structural relaxation time using the T ool-Narayanaswamy-Moynihan formalism. For a given glass composition, t he stretched exponential parameter, beta, the activation energy, DELTA h, the non-linearity parameter, x, and the fitted relaxation time A (a s T and T(f) --> infinity) are independent of the cooling and heating rates. This indicates the adequacy of the formalism for these glasses. Initial addition of AgI increases the parameter beta, related to the breadth of the relaxation time distribution, which remains constant on further addition. DELTAh, x and A decrease systematically with the am ount of AgI in the glass. It is suggested that a more appropriate defi nition of the glass transition temperature, T(g), of a glass can be ac hieved by determining its relaxation time at different temperatures, r ather than the usual methods of tangent intersection. This eliminates the effects of variation of beta, DELTAh and x on the usual calorimetr ic T(g) of different glasses.