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

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 (x(Pt)=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. (C) 1999 Elsevier Science S.A. All rights reserved.