Thermodynamic investigation of ternary Pt–Pd–Ge alloys by Knudsen effusion combined with mass spectrometry

Abstract

The activities of the three components of Pd–Pt–Ge ternary melts were measured by Knudsen effusion combined with mass spectrometry according to Belton and Fruehan's method. Four pseudo-binary lines with constant mole fraction of platinum (xPt=0.10, 0.20, 0.35 and 0.50) were investigated. The excess free enthalpy of formation of the ternary melts at 1820 K over the whole range of composition was deduced. The data obtained allowed us to apply the associated solution model to the thermodynamic functions of the Pd–Pt–Ge ternary system and to elucidate the nature and the temperature dependence of its short-range order as reported previously.