Thermodynamic assessment of the Ce-Co-Sb ternary system

On the basis of all the presently determined experimental data, as well as the formerly reported isothermal sections of the Ce-Co-Sb ternary system, it was thermodynamically assessed by means of CALPHAD technique. For Ce-Co and Co-Sb binary systems, thermodynamic parameters previously obtained were considered and a re-assessment work of the Ce-Sb system is presented. In particular, the Kaptay exponential model, rather than the Redlich-Kister polynomials, is used to describe the interactions between Ce and Sb in the liquid phase of the Ce-Sb system, mainly to avoid the abnormal miscibility gap of liquid phase in the Ce-Co-Sb system at the Co rich region, and also to guarantee the consistent phase equilibria between the experimental isothermal sections and the calculated ones of the Ce-Co-Sb ternary system. The ternary compound CeCouSb2 is modeled as Ce2/9(Co%,Va)1/3Sb4/9 in order to describe the fluctuation of Co atoms in this compound. The ternary compound CeCoSb3 is regarded as a stoichiometric phase. The previously optimized thermodynamic parameters of other phases were adopted in the present work. A set of self-consistent thermodynamic parameters were finally obtained and fit well with the experimental results from various literatures, which will contribute to the further development of the CoSb3-based thermoelectric materials, especially from the perspective of the couping of electron-phonon interactions.