Enthalpies of formation of liquid and solid (palladium + indium) alloys

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I.

INTRODUCTION

THERMODYNAMIC properties of liquid alloys of a transition metal with an element of group IliA (A1, Ga, In) are not well known. The high temperature needed and the easy reaction of the melt with oxygen, nitrogen, or the crucible material make experiments difficult. The application of models like the semiquantitative model by Miedema (de Boer e t al. t~j) was of great promise, but the results computed sometimes did not even give the right order of magnitude, as e . g . , for Au + Ga, t21 Au + Al,t3] P d + Ga, t41 or Ni + Ga. tSJ Other models, as simple as the regular or the subregular solution, t6] need some experimental data with high precision. The present work is part of a systematic study of the thermodynamic properties of liquid binary alloys composed of an element of group IIIA (A1, Ga, and In) and a transition metal from groups VIIIB and l B . I2-4'7'8]. The phase diagram has recently been reviewed by Okamoto. t9j Three of the six compounds mentioned melt congruently, Pdln,/3-Pd2In, and/3-Pd3In at 1558, 1596, and 1638 K, respectively. By exhibiting a broad range of homogeneity (about 0.48 < xpd < 0.615) the Pdln phase (CsCI type) dominates the phase diagram, whereas all other phases have a much smaller homogeneity range. Bryant and Pratt r~~ determined the enthalpies of formation of solid Pd3In, Pd2In, Pdln, Pd2In3, Pdln3, and PdsIn3 at 320 K by tin solution calorimetry and the limiting partial enthalpy of solid indium in solid palladium. Vogelbein e t al. t~J investigated the enthalpies of formation of Pd088In0.12 and Pd0.75In0.25by lead solution calorimetry and the limiting partial enthalpy of palladium in liquid indium at 1000 K. Colinet e t al. t~21 obtained the limiting partial enthalpy of solid palladium in liquid indium at 1090 K. Darby e t al. 1131performed tin solution DRISS EL ALLAM, formerly Ph.D. Student, Universit6 de Provence, MARCELLE GAUNE-ESCARD, Director of Research, and JEAN-PIERRE BROS, Professor, Universit6 de Provence, are with IUSTI-UA 1168, Centre de Saint Jrr6me, Marseille Cedex 20, France. ERHARD HAYER, Assistant Professor, is with the Institute of Inorganic Chemistry, University of Vienna, 1090 Vienna, Austria. Manuscript submitted November 1, 1993. METALLURGICALAND MATERIALSTRANSACTIONS B

calorimetry measurements for three a-phase palladiumrich alloys of Pd-In. Anantatmula 114~ measured the vapor pressure of indium for some PdIn alloys at 1043 K by atomic absorption spectroscopy. Bird e t al. II51 investigated the thermodynamic properties of the different palladium-indium solid alloys (a-phase and intermediate phases Pd3In, Pd2In, PdsIn3, PdIn, Pd2In3, and PdIn3) at 873 K by an electromotive force (emf) method employing a solid electrolyte (ZrO2CaO) and by DSC, respectively. From the activities of In at 873 K, partial and integral Gibbs energy values were calculated and integral molar entropies of formation derived combining the data with the enthalpies of formation ll~ obtained at 320 K. Schaller and Brodowsky 1~61performed emf measurements with an oxygen-conduct