Sub-Tg enthalpy relaxation in a milling-derived chalcogenide glass

In this work we succeeded in synthesizing a chalcogenide glass, that is, the Ag 3 PS 4 glass, by milling the mixture of the crystalline Ag 2 S and P 2 S 5 powder. In terms of potential energy, the glass was excited by the milling process. The evidence for the energy excitation was the occurrence of the sub- T g relaxation recorded by a differential scanning calorimeter (DSC). The relaxation behavior in the milling-derived Ag 3 PS 4 glass was found to significantly differ from that of a hyperquenched oxide glass. We observed two decoupled peaks of the energy release during a DSC scan, which are in contrast to the single asymmetric peak of the hyperquenched glass. The low-temperature peak could be attributed to the β-relaxation of the Ag–S ionic bonds, whereas the high-temperature peak could arise from the α-relaxation of the distorted rigid [PS 4 ] units involving covalent bonds. The decoupling between the two peaks implies the fragile nature of the Ag 3 PS 4 glass. Upon the dynamic heating and the sub- T g annealing we found that the relaxation of the Ag 3 PS 4 glass is of high nonexponentiallity, and hence, of high structural heterogeneity.