ENTHALPY OF FORMATION OF GOLD-TELLURIUM LIQUID ALLOYS

According to the literature, the enthalpy of formation of the Au-Te me lts, Delta h(f) is negative, at low temperature (737 K and 769 K) on t he Te-rich side and changes its sign with composition. However, at hig h temperature (T greater than or equal to l000 K), Bergman's data lead s to negative excess heat capacity whereas those of Hayer yield the op posite conclusion when compared with low temperature results, That is why, in this work, we determined the enthalpy of formation at five dif ferent temperatures between 751 and 1000 K. The results from this work are in agreement with Castanet et al. at 737 K and with Ishida et al. at 769 K. They show that the enthalpy of mixing changes its sign with composition and becomes positive on the Au-rich side and less negativ e with increasing temperature on the Te-rich side. Indeed, in the comp osition range investigated (0.5 less than or equal to x(Te)less than o r equal to 1), the enthalpy of mixing does not depend on temperature f rom 737 to 819 K nor from 872 to 1000 K. However, it increases between 819 (Delta h(min)(f)=-1098 J mol(-1)at x(Te)=0.630) and 872 K (Delta( min)(f)=-628 J mol(-1) at x(Te) =0.690).