Enthalpy of formation for CoGe, CoSn, Ni3.14Sn4, Ni3.50Sn4, AuCo1.66Sn4, AuNi2Sn4 and Au1.17Pt1.82Sn4

The enthalpies of dissolution, H-diss, of CoGe, CoSn, Ni3.14Sn4, Ni3.50Sn4, AuCo1.66Sn4, AuNi2Sn4 and Au1.17Pt1.82Sn4 and their components have been m easured in molten tin at 874 K by drop calorimetry. The enthalpy of formati on of these phases, Delta H-f(298), has been derived for 298 K. Earlier mea surements of the enthalpy of formation for the elements, disregarding cobal t, are in close agreement with the present results. The values for pure Co show significant temperature dependence, and also deviate from earlier find ings. For the binary and ternary phases the accordance with earlier results for the Ni3 + vSn4 phase is perhaps acceptable when the differences in spe cimen compositions are taken into account. The corresponding comparison for CoGe and CoSn has a much poorer outcome. The latter discrepancies are tent atively coupled to distinctions between the species of dissolved cobalt in liquid tin at different temperatures. No enthalpy of formation measurements have been reported for any of the ternary phases. Comparison of theoretica lly computed data for the enthalpy of formation for the binary and ternary phases shows close agreement with the measured values obtained in this stud y. (C) 2000 Elsevier Science S.A. All rights reserved.