TEMPERATURE-DEPENDENCE OF ENTHALPY OF FORMATION OF LIQUID GE-TE ALLOYS

Enthalpies of formation h**f of Ge-Te alloys were measured by direct reaction calorimetry in the temperature range 1030 less than T/K less than 1150 and at mole fractions 0. 25 less than x//G//e less than 1. The measurements were performed with a high temperature (T/K less than 1400) Tian-Calvet calorimeter. When referred to liquid tellurium and liquid germanium, the enthalpy of formation is strongly negative in the whole investigated composition range (at T/K equals 1028 and x//G//e equals 0. 46, h**f(minimum) equals minus 14. 8 kJ mol** minus **1) and appears to be very sensitive to temperature (C**E//p equals 19. 3 J mol** minus **1 K** minus **1 at x//G//e equals 0. 5). Such a behaviour is consistent with the existence of Ge-Te associations in the liquid state, disappearing with increasing temperature.