Thermodynamic study of zinc antimonides by the electromotive force measurements

Zinc antimonides and phases based on them are of great interest as earth-abundant, low-cost, and environmentally friendly thermoelectric materials. The present work demonstrates the results of a thermodynamic study of the ZnSb and Zn4Sb3 compounds by a low-temperature electromotive force (emf) method with a glycerol electrolyte in the 300-430 K temperaturesrange. Measurements were performed using equilibrium samples from the ZnSb+Sb and ZnSb+Zn4Sb3 two-phase regions of the Zn-Sb binary system. The phase compositions of prepared samples were controlled by means of the powder X-ray diffraction (PXRD) method. Using the least square method, the linear equations of temperature dependences of the emf data wereobtained. Based on these equations and relevant thermodynamic expressions, the partial molar Gibbs free energy, enthalpy, and entropy of zinc in alloys were calculated. Utilizing the phase diagram of the Zn-Sb system, the virtual-cell reactions for both binary compounds were determined, based on which their standard hermodynamic functions of formation and standard entropies were calculated. A comparative analysis of the obtained results with available literature data was carried out. The results of the current work are highly accurate and can be considered a new contribution to the thermodynamics of zinc antimonides