THERMODYNAMIC INVESTIGATION OF THE SOLID AND LIQUID AU-SB ALLOYS

The heat content of solid and liquid AuSb2 compound was measured from 298 K to T (375-963 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 between the melting point and 831 K. The enthalpy of formation of the Au-Sb melts was also determined by direct reaction calorimetry at 916 K with respect to concentration. The enthalpy of mixing is weakly negative in the whole range of concentration (h(min)f = -3.47 kJ/mol at x(Au) = 0.775) in agreement with the results of Beja at 923 K. Our data disagree with the much more negative earlier data of Kameda et al. and of Hino et al. by emf and vapor pressure measurements. Finally, the liquid/Au(cr) phase boundary determined at 916 K from the break in the h(f) (x(Au) curve agrees well with the phase diagram calculated by Okamoto and Massalski but not with their experimental results.