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

Calorimetric and dilatometric thermal properties of bulk GexSb40-xSe60 glas ses (x = 15, 20, 25, 27, 32, 35) have been investigated by differential sca nning 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 coor dination number Z have been specified. It has been found from the dependenc e of T-g on the heating rate that the parameter B, related to configuration al changes in the structure, reaches a maximum at Z = 2.67 (i.e. for Ge-27 Sb-13 Se-60), while Delta C-p values remain almost constant at Z 12.67. The apparent activation energy of glass transition E-t for both the methods ha s been compared. Threshold-like behaviour at Z = 2.67 of the change in the fragility in has also been observed for both the methods. The softening tem perature T-s and the coefficient of thermal expansion in glass alpha(g) det ermined by TMA have exhibited a feature at Z = 2.67 as well. (C) 2000 Elsev ier Science B.V. All rights reserved.