Studies on GexSb40−xSe60 glasses by differential scanning calorimetry and thermomechanical analysis

Calorimetric and dilatometric thermal properties of bulk GexSb40−xSe60 glasses (x = 15, 20, 25, 27, 32, 35) have been investigated by differential scanning calorimetry (DSC) and thermomechanical analysis (TMA). The variations of the difference in specific heat capacity between glass and undercooled liquid ... Cp and of the glass-transition temperature Tg on the average coordination number Z have been specified. It has been found from the dependence of Tg on the heating rate that the parameter B, related to configurational changes in the structure, reaches a maximum at Z = 2.67 (i.e. for Ge27 Sb13 Se60), while ΔCp values remain almost constant at Z ≥ 2.67. The apparent activation energy of glass transition Et for both the methods has been compared. Threshold-like behaviour at Z = 2.67 of the change in the fragility m has also been observed for both the methods. The softening temperature Ts and the coefficient of thermal expansion in glass αg determined by TMA have exhibited a feature at Z = 2.67 as well.