Thermodynamics of intermetallics through emf measurements under effusion conditions,

A general treatment is performed for a complete description of the thermodynamics of galvanic cells type working under effusion conditions where the vaporization of Me” is considered. The treatment has been applied to three Me2Ni17 /Niss systems with Meº Eu, Tb, Ho and MehMe'k is the solid solution, Niss, produced by the eutectic reaction L « Me2Ni17(s) + Niss. From the emf vs T experimental data, and have been calculated. The values for Tb2Ni17(s) and Ho2Ni17(s) are, respectively, -16.76±0.06 and -18.8±0.1 kJ /mol atoms. In the same order, the values are -1.27±0.06 and -1.81±0.09 JK-1/ mol atoms, respectively, at equal 1023 and 1085 K. For Eu2Ni17(s), and are, respectively, -48±4 kJ /mol atoms and 2.0±0.2 JK-1/ mol atoms, both the values at =910 K. The latter results should be considered unexpected and the reason of this is extensively discussed.