Résumé: The values of the thermal heat-capacity changes at the glass transition temperature Tg ([Delta]Cp=Cpl-Cpg) and the values of the apparent activation energy [Delta]h* of the sub Tg relaxation process are determined for GexTe1-x (0.15[les]x[les]0.20) vitreous alloys by means of differential scanning calorimetry investigations. The values of [Delta]h* are then used to determine the values of the fragility index, m. The comparison of these new data to those already obtained on the GexSe1-x vitreous system leads to conclude that both systems exhibit strong thermodynamic character. The stronger thermodynamic character is reached at the Phillips-Thorpe's floppy-to-rigid transition. On the other hand, we find that GexTe1-x exhibits a kinetically fragile character which decreases as the amount of Ge increases in the alloy.

Langue: Anglais