Synthesis, Thermodynamic Properties, and Structural Characteristics of Multicomponent Compounds in the Ag–Ni–Sn–S System

To establish an accurate thermodynamic database of the Ag–Ni–Sn–S system, only a few experimental studies have been published. There is no published work with thermodynamic values of the quaternary compounds of the Ag–Ni–Sn–S system. Therefore, the main objective of this work was to determine the thermodynamic properties of multicomponent phases in the Ag–Ni–Sn–S system and to contribute new experimental thermodynamic data for the relatively better known phases in the temperature and compositional ranges that have not been studied experimentally before. To achieve these objectives, the T–x space of the Ag–Ni–Sn–S system in the region SnS–SnS ₂–NiS ₂–NiS–Ag ₂S–SnS was studied by the x-ray phase diffraction and modified electromotive force (EMF) methods. The existence of the multicomponent compounds AgNiS ₂, Ag ₂NiS ₂, Ag ₂NiSnS ₄, and Ag ₂NiSn ₃S ₈ below 600 K was established. The synthesis was carried out in the positive electrodes of the electrochemical cells (ECCs). The values of standard thermodynamic functions of the compounds were determined from the temperature dependencies of the EMF of the ECCs. The crystal structure of the new modification of Ag ₂NiSn ₃S ₈ compound was studied by x-ray diffraction analysis.