Thermodynamic Study of Copper Antimonides by the EMF Method with the Cu₄RbCl₃I₂ Solid Electrolyte

Copper antimonides and phases based on them are of great interest as environmentally friendly functional materials for potential application in various areas of industry and technology. Present work demonstrates the results of thermodynamic study of Cu₄Sb and two polymorphic modifications of Cu₂Sb by low temperature electromotive force method (EMF) with a Cu⁺ conducting solid electrolyte RbCu₄Cl₃I₂ in 300–480 K temperatures range. Measurements were performed using equilibrium samples from the Cu₂Sb + Sb and Cu₄Sb + Cu₂Sb phase regions of the system. Phase compositions of samples were controlled using the powder X-ray diffraction (PXRD) method. Partial molar thermodynamic functions of copper in alloys, as well as, thermodynamic functions of formation and the absolute entropies of the RT–Cu₂Sb, HT–Cu₂Sb, and Cu₄Sb compounds were calculated. The enthalpy and entropy of the polymorph transition of Cu₂Sb were calculated based on the EMF data. A comparative analysis of obtained results with literature data was performed.