Correlation between the structure and relaxation dynamics of (GeS2)y(Sb2S3)1 − y glassy matrices

Differential scanning calorimetry was used to study enthalpy relaxation kinetics of the (GeS2)y(Sb2S3)1 − y glasses in the y = 0.1-0.9 compositional range. The relaxation behavior was described in terms of the phenomenological Tool-Narayanaswamy-Moynihan (TNM) model. Non-linear optimization procedure was used to determine unique set of relaxation parameters for each studied glass. With increasing GeS2 content the activation energy of enthalpy relaxation was found to steeply decrease whereas the glass transition temperature increased significantly. Both non-linearity and non-exponentiality features were not affected by compositional changes. Raman spectra have shown that the Ge-S structural units, as opposed to the Sb-S units, are significantly interconnected and create a 3-dimensional network capable of solely carrying the relaxation motions, which is in agreement with the interpretation of compositional evolution of relaxation parameters. Moreover, based on the present data the controversy regarding the (GeS2)y(Sb2S3)1 − y fragilities found in literature was clarified, and the free-volume concept employing the Avrami growth theory was disputed.