Thermodynamic Investigation of Solid and Liquid Au-Te Alloys

The heat content of solid and liquid AuTe 2 compound was measured from 298 K to T (471-1022 K) on heating (drop method) with the help of a Tian-Calvet calorimeter. The heat capacity of the liquid compound as well as its enthalpy of fusion were deduced. The enthalpy of the liquid decreases strongly when temperature increases especially for T>923K. Such a behaviour cannot be explained easily by the existence of a short-range order since the enthalpy of formation is only weakly negative. The enthalpies of dissolution of Au and AuTe 2 in Au-Te melts were also determined by direct reaction calorimetry at 728 K with respect to concentration (0 < x Au < 0.18 and 0 < x AuTe 2 < 0.27). With the help of the heat content data determined previously we calculated the enthalpy of formation of the AuTe 2 compound at 298 K (− 3.3 kJ per mole of atoms). Such a low negative value as well as the low melting temperature agree well with the assumption of some associated state of the liquid in spite of the weakly negative enthalpy of mixing.