Interpretation of Tool–Narayanaswamy–Moynihan relaxation parameters

Abstract

Differential scanning calorimetry (DSC) measurements were used to study enthalpic structural relaxation in selenide glasses. The examined compositions were, apart from pure Se, the following Se(100–y)Tey (for y = 0.1, 0.2 and 0.3), GeySe(100–y) (for y = 0.02, 0.04, 0.06, 0.08, 0.10 and 0.15) and AsySe(100–y)Tey (for y = 0.02, 0.04, 0.06, 0.08 and 0.10). Based on the results of fitting and non-fitting methods, relaxation behavior of these glasses was described in terms of the Tool–Narayanaswamy–Moynihan (TNM) model. The TNM model parameters as well as their change with respect to both increasing content of dopant in Se matrix within each chalcogenide system and different structural units employed in the respective systems were discussed. A unique conception was suggested, introducing a connection between the values of TNM parameters and respective molecular structures and their changes during structural relaxation. By such qualitative interpretation, the main disadvantage of phenomenological models may be, at least partially, overcome.