Thermodynamic descriptions and phase diagrams for Sb–Na and Sb–K binary systems

• The Sb–Na and Sb–K binary systems are optimized using the CALPHAD technique.
• The associated solution model is used to describe the liquid phase.
• Self-consistent thermodynamic parameters for such two binary systems are obtained.

Based on the experimental characterizations, including thermochemical properties and phase equilibrium data, the Sb–Na and Sb–K binary systems are modeled within the CALPHAD framework. The Sb–Na and Sb–K melts are treated with the associated solution model, in which Na3Sb and K3Sb associates are assumed to exist, respectively. The binary intermetallics, i.e. Na3Sb, NaSb, K3Sb, K5Sb4, KSb and KSb2 are modeled as stoichiometric phases. Such models allow the peculiarities of related thermochemical properties and phase diagrams to be well reproduced, especially for the V-shaped enthalpies/entropies of mixing, abrupt changes in activity plots and sharp liquidus around Na3Sb, KSb and K3Sb intermetallics. Although the experimental data are scattered to some extent, the thermodynamic descriptions provided in this work can satisfactorily represent a great majority of such measured quantities.