Thermodynamic description of the Eu-Ga system using substitutional solution and associate models

The Eu-Ga system is first optimized by the CALculation of PHAse Diagrams (CALPHAD) technique based on the experimental data in the literature. The associate model for the liquid phase is tested and compared with the substitutional solution model given the asymmetric shape of the liquid in the Eu-Ga phase diagram. Description results show that the associate model achieved better consistency with the available experimental data than the substitutional model. The liquid significantly deviates from the regular solution and shows association between Eu and Ga. The excess Gibbs energies of the solution phases (e. g., liquid, bcc, orthorhombic) are modeled through the Redlich-Kister polynomial functions. Intermetallics, such as Eu${}_5$Ga${}_3$, EuGa, Eu${}_2$Ga${}_3$, EuGa${}_2$, Eu${}_2$Ga${}_5$, and EuGa${}_4$, are treated as stoichiometric compounds. This work shows that the Eu-Ga system hosts two eutectic, five peritectic, and one congruent reactions. Two sets of parameters for self-consistent thermodynamic description of the Eu-Ga binary system are obtained.