Standard enthalpies of formation of some Lanthanide-Cobalt binary alloys by high temperature direct synthesis calorimetry

The standard enthalpies of formation of intermetallic compounds of some Lanthanide-Cobalt systems have been measured by high temperature direct synthesis calorimetry at 1373 ± 2 K. The following results in kJ/mol of atoms are reported: CeCo5(−9.4 ± 3.3); Ce2Co17(−6.8 ± 3.2); PrCo5(−10.5 ± 2.4); Pr2Co17(−6.8 ± 3.6); NdCo5(−12.7 ± 2.6); Nd2Co17(−6.6 ± 2.7); SmCo5(−12.2 ± 1.8); Sm2Co17(−7.2 ± 2.5); GdCo5(−10.0 ± 2.4); Tb2Co17(−7.7 ± 2.9); Dy2Co17(−8.1 ± 2.9); HoCo3(−17.5 ± 2.2); ErCo3(−19.7 ± 3.3); TmCo3(−22.9 ± 3.0); LuCo3(−23.0 ± 2.6). The measurements are compared with values from the literature and with predicted values of the semi empirical model of Miedema and Coworkers. We also compare the measurements with predicted values by ab initio calculations. We will present a systematic picture of how the enthalpies of formation may be related to the atomic number of the Lanthanide element (LA). We will also compare the thermochemical behavior of the Fe, Co and Ni binary alloys with Lanthanide elements.