Relaxation processes in Se-rich chalcogenide glasses: Effect of characteristic structural entities

Structural relaxation processes were studied by means of differential scanning calorimetry for a number of compositions belonging to the Se-rich sides of Se–Te, Ge–Se and As–Se chalcogenide systems. Based on the results of fitting and non-fitting methods, the relaxation behavior of these selenide glasses is described in terms of the Tool–Narayanaswamy–Moynihan (TNM) equations. The goal of this paper is to introduce an advanced model describing the relationship between the macroscopic relaxation behavior and molecular structure of the glass. Special attention is paid to differences between the particular structural units and molecular arrangements characteristic for each system studied. The TNM parameters as well as their changes are discussed with respect to both the increasing content of dopant in the Se matrix within each chalcogenide system and different structural units employed in the respective systems. A unique novel conception is suggested, showing a connection between the values of TNM parameters and respective molecular structures and their changes during structural relaxation.