Standard enthalpies of formation of some rare earth carbides by direct synthesis calorimetry

Abstract

The standard enthalpies of formation of carbides in the binary systems Sc-C, Y-C and La-C have been determined by direct synthesis calorimetry at 1473 ± 2 K. The following values are reported: ΔH f 0(Sc 2C) = −45.5 ± 1.6 kJ (g atom) −1; ΔH f 0(Y 2C) = −31.8 ± 1.3 kJ (g atom) −1 and ΔH f 0 (LaC 2) = −27.2 ± 1.4 kJ (g atom) −1. The results are compared with earlier experimental data and with values predicted from Miedema's semi-empirical model. The enthalpies of formation for the carbides considered are also compared with the corresponding data for silicides and germanides.