Structural interpretation of the viscous flow and relaxation kinetics in the As-Se and Ge-Se chalcogenide systems

This study investigates the behaviour of As₂₀Se₈₀ and Ge₂₅Se₇₅ chalcogenide glasses near the glass transition temperature using differential scanning calorimetry (DSC) and thermomechanical analysis (TMA), addressing a gap in the literature for these compositions. Precise TMA measurements of viscosity in the range of 10⁶ – 10¹³ Pa·s clarified existing data and improved the quality of fits describing the temperature-dependent viscosity for both compositions. The DSC method enabled a comprehensive analysis of structural relaxation behaviours, which were described using the Tool-Narayanaswamy-Moynihan (TNM) model with the determination of its four parameters. The study discusses the viscosity and structural relaxation behaviours of both glass-formers in relation to their structure, referencing previous results for other binary chalcogenide glasses in the As-Se and Ge-Se systems. The findings indicate significant changes in viscosity and activation energy of structural relaxation with the addition of As or Ge, while the non-linearity and non-exponentiality parameters remain largely unaffected.