Vaporization and thermodynamic properties of samarium dicarbide and sub-stoichiometric disamarium tricarbide

Abstract

The vaporization reactions of SmC2(s) and Pu2C3-type SmCy(s, 1.36 y SmC2(s) = 2C(s)+Sm(g){2/(2-y)}SmCy(s) = {y/(2-y)}SmC2(s)+Sm(g)The complex reaction for SmCy occurs because the composition of the carbon-rich boundary of the phase decreases as temperature increases. For reaction (i), the equiliblium pressure is described by log10{(p/po)(Sm, g, 1548 K T T/K)-1. The non-linear pressure equation for reaction (ii) is log10{(p/po)(Sm, g, 1.42 y T T/K)-1 + 7018500(T/K)-2 +/- 0.038}. Thermodynamic values for the vaporization and formation reactions of SmC2(s) and SmCy(s) at 298.15 K have been calculated: [Delta]Hto(SmC2, s, 298.15 K) = -(96.2 +/- 7.5) kJ [middle dot] mol-1 and [Delta]Hfo(SmC1.43, s, 298.15 K) = -(89.0 +/- 8.0) kJ [middle dot] mol-1. The thermodynamic results are discussed and compared with values reported for other lanthanide carbides.