On the compositional diversity of physical aging kinetics in chalcogenide glasses

Compositional features of enthalpy losses ΔH(t) caused by long-term physical aging at normal conditions are studied at the example of Se-rich chalcogenide glasses As20Se80, As30Se70 and Ge5Se95 obeying “chain-crossing” structural model. The observed relaxation kinetics in general are described by a stretched exponential behavior, but can be also parameterized in terms of multi-step single exponential decays. Microstructural mechanism of natural physical aging in the studied glasses is explained by accepting their structural-topological specificity with a decisive role of preferential chemical environment around Se atoms. The characteristic time constants of aging are shown to increase in more topologically constrained structural fragments capable to relaxation. Independent relaxation stages originated from different chemical environments in As10Se90 and Ge5Se95 glasses allow observation of plateau-like behavior. However, plateaus are found to be smoothed in As20Se80 glass because of overlap of different structural complexes responsible for relaxation.