Thermodynamic properties of RE2Co17 intermetallics at high temperatures (RE = Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu)

Abstract A set of thermodynamic properties of the Co rich part of the Co/rare earth (RE) systems is presented for almost all the elements in the rare earth series. This set of data comes entirely from the emf vs. T experimental measurements obtained by galvanic cells with CaF 2 single crystal as electrolyte. The standard enthalpy and entropy of formation of RE 2 Co 17 intermetallics have been obtained and compared with previous results found for the RE 2 Ni 17 and RE 2 Fe 17 intermetallics. The values of the enthalpy of formation of RE 2 Co 17 intermetallics are intermediate between the two series above. The RE 2 Co 17 entropy of formation is positive from Pr to Dy and negative from Ho to Tm. The value of Lu 2 Co 17 is notably positive. The RE solubility in Co has been evaluated by the shift of the fcc Co (200) lattice parameter with respect to the pure Co as shown by the corresponding XRD feature. Along the RE examined, the activity at 1000 K of RE in the Co solid solution changes from (7.1 ± 0.1) · 10 −6 for Dy to (3.8 ± 0.2) · 10 −4 for Pr.