Thermodynamic Investigation of the Pd–Pt–Ge Ternary Alloys at 1269 K

Abstract

AbstractThe enthalpy of formation, ∆f H of the Pd–Pt–Ge alloys was measured at 1269K with respect to composition by direct reaction calorimetry (drop method) with the help of high-temperature Calvet-type calorimeters. The measurements were performed at four values (0.10, 0.25, 0.50 and 0.75) of R = x Pt/x Pt+x Ge and one (0.60) of R′ = x Pd/x Pd+ x Ge From the breaks of the enthalpy curves with respect to composition for given R and R′values we obtained evidence for the existence of a series of Pd2Ge–Pt2Ge solid solutions as well as the boundaries of the liquid + solid solution domains. We also deduced the enthalpy of formation of the Pd2Ge–Pt2Ge solution with respect to composition. The Pd2Ge–Pt2Ge pseudo-binary can be considered as ideal.The thermodynamic behaviour of the melts is characterized by strong negative deviations from ideality, as was also the case for the Pd–Ge and Pt–Ge binaries. The isoenthalpic curves at 1269 K show that the minimum of the enthalpy lies on a straight line from pure Pd2Ge ...