Thermodynamic assessment of the Si–Ta system

The thermodynamic modeling of the silicon–tantalum binary system was carried out with the help of the CALPHAD (CALculation of PHAse Diagram) method. A solution model was used for the description of the liquid and bcc phases while the Si2Ta, Si3Ta5_LT, Si3Ta5_HT SiTa2 and SiTa3 compounds are treated as stoichiometric. The excess Gibbs energy function of the solution phases was assessed with the recent exponential temperature dependence of the interaction parameters by Kaptay [1], [2] and [3] and compared with the Redlich–Kister [4] polynomial equation results. The calculations based on the thermodynamic modeling are in good agreement with the phase diagram data and experimental thermodynamic values available in literature.

► The thermodynamic modelling of the Si–Ta system is made with the CALPHAD method.
► The liquid and bcc phases are treated with a solution model and compounds as stoichiometric.
► The excess Gibbs energy of the solution phases is assessed with the T dependence by Kaptay.
► The calculations based on the thermodynamic optimisation agree well with the experiments.