Calorimetric studies of structural relaxation in AgIAgPO3 glasses

Abstract

Abstract Differential scanning calorimetry data of AgPO3 and AgIAgPO3 glasses have been described in terms of structural relaxation time using the Tool-Narayanaswamy-Moynihan formalism. For a given glass composition, the stretched exponential parameter, β, the activation energy, Δh, the non-linearity parameter, x, and the fitted relaxation time A (as T and Tf → ∞) 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 β, related to the breadth of the relaxation time distribution, which remains constant on further addition. Δh, x and A decrease systematically with the amount of AgI in the glass. It is suggested that a more appropriate definition of the glass transition temperature, Tg, of a glass can be achieved by determining its relaxation time at different temperatures, rather than the usual methods of tangent intersection. This eliminates the effects of variation of β, Δh and x on the usual calorimetric Tg of different glasses.