Thermodynamic Investigation of the Pt—Pb Binary Alloys

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AbstractThe enthalpy of formation, hf, of the Pt—Pb alloys was measured in the 923–1316 K temperature range with respect to composition by direct reaction calorimetry (drop method) with the help of high temperature Calvet‐type calorimeters. Furthermore we determined also some phase boundaries from the breaks of the hf(x) curves. — The thermodynamic behaviour of the melts is characterized by moderate negative deviations to ideality suggesting some chemical short‐range order (h = −15.88 kJ · mol−1 at 923 K for χPt = 0.53). The associates are very sensible to temperature since the excess heat capacity is positive with a maximum of about 10.2 J · K−1 · mol−1 near χPt = 0.71. Such a behaviour differs strongly from that of the Pd‐Pb system which shows a strongly negative enthalpy of mixing (h = −38.4 kJ · mol−1) without any temperature dependence.