Thermodynamic assessment of the Cu-Ge binary system

The Cu-Ge binary system was assessed thermodynamically using the CALPHAD method through Thermo-calc® software package based on the evaluation of all available experimental data from the published literature. The solution phases, including liquid, fcc, hcp and diamond (Ge), were described by the substitutional solution model, of which the excess Gibbs energies were expressed with the Redlich-Kister polynomial. Due to their narrow homogeneity ranges, all intermetallic compounds, ɛ-Cu0.765Ge0.235, θ-Cu0.735Ge0.265 and η-Cu0.75Ge0.25, were modeled as stoichiometric compounds. A set of self-consistent thermodynamic parameters formulating the Gibbs energies of various phases in the Cu-Ge binary system was obtained finally. A good agreement is achieved between the calculated results and the reported experimental data.