Enthalpy and Gibbs energy of formation of dysprosium dicarbide

The equilibrium CO(g) pressures have been determined over the univariant three-phase field DyO1.5(s)–C(s)–DyC2(s) by means of the dynamic effusion MS method, in the temperature range 1360–1590 K. The carbide phase was generated in situ by the carbothermic reduction of the oxide using a quadrupole mass spectrometer, the effusion pressure of carbon monoxide was monitored. The enthalpy of the carbothermic reduction reaction was calculated by second- and third-law methods. By combining the appropriate thermal functions and enthalpies of other constituents from standard thermodynamic tables, the enthalpy of formation of the dicarbide at 298 K has been calculated. The Gibbs energy of formation of the dicarbide in this temperature range has also been calculated. The recommended values of enthalpy and Gibbs energy of formation of DyC2(s) at 298 K are −(131 ± 19) kJ mol−1 and −(165 ± 6) kJ mol−1, respectively.