Sn-Sb alloys are important high-temperature solders. However, inconsistencies are found in the available phase diagrams, and some phase boundaries in the Sn-Sb system have not been determined. Sn-Sb alloys were prepared, equilibrated at 160°C to 300°C, and the equilibrium phases and their compositions were determined. The b-SnSb phase has a very wide compositional homogeneity range, and its composition varies from Sn-47.0at.%Sb to Sn-62.8at.%Sb. There is no order-disorder transformation of the b-SnSb phase. There are three peritectic reactions in the Sn-Sb system, L + Sb = b-SnSb, L + b-SnSb = Sn 3 Sb 2 , and L + Sn 3 Sb 2 = Sn, and their temperatures are 424°C, 323°C, and 243°C, respectively. Thermodynamic models of the Sn-Sb binary system were developed using the CALPHAD approach based on the experimental results of this study and the data in the literature. The calculated phase diagram and thermodynamic properties are in good agreement with the experimental determinations.

The stability of intrinsic point defects in PbTe, one of the most widely studied and efficient thermoelectric material, is explored by means of Density Functional Theory (DFT). The origin of nand p-type conductivity in PbTe is attributed to particular intrinsic charged defects by calculating their formation energies. These DFT calculated defect formation energies are then used in the Gibbs free energy description of this phase as part of the Pb-Te thermodynamic model built using the CALPHAD method, and in the resulting phase diagram it is found that its solubility lines and non-stoichiometric range agree very well with experimental data. Such an approach of using DFT in conjunction with CALPHAD for compound semiconductor phases that exhibit very small ranges of non-stoichiometry does not only make the process of calculating phase diagrams for such systems more physical, but is necessary and critical for the assessment of unknown phase diagrams.

The Cu–Sn binary system is important for various applications, especially for recent developments in the electronics packaging industry. The ϵ-Cu3Sn and η-Cu6Sn5 (η′ phases) phases are frequently encountered in electronics products. However, the two phases have been described as line compounds in previous thermodynamic modeling, and their compositional homogeneities were not considered. In this study, the thermodynamic properties of the Cu–Sn binary system are modeled and the phase diagram is calculated by the CALPHAD method, using experimental information reported in the literature. The ϵ and η (η′) phases are described using compound energy models with two and three sublattices, respectively, so that their compositional homogeneities could be calculated. Good agreement was observed between the calculated result and the existing experimental data.