Thermodynamic stability of palladium alloys: Part I: The palladium-niobium system

The palladium activities of 12 palladium-niobium alloys (compositions from 60Pd40Nb to 97Pd3Nb) have been determined experimentally with a twin-chamber Knudsen cell mass spectrometer between 1450 and 1750 K. From the measured aPd data, other relevant thermo-dynamic properties are calculated. The ΔGf o and ΔHf o of Pd-Nb alloys thus obtained are com-pared with the published values estimated on the basis of empirical models. The results of the present work show a strong attractive interaction in the solid state between the palladium atoms and the niobium atoms. The measured palladium activities show a strong negative deviation from the ideal solution behavior.