Abstract

Purpose. This work is aimed at synthesis and cgrowth, X-ray investigation, study of the phase diagram and concentration behavior of lattice parameter and density of (Cu_1-хAg_x)₇SiS₅I solid solutions.
Methods. Alloys of Cu₇SiS₅I – Ag₇SiS₅I system were synthesized by means of direct one-temperature method from pre-synthesized Cu₇SiS₅I and Ag₇SiS₅I compounds. Growth of single crystals of (Cu_1-хAg_x)₇SiS₅I solid solutions was carried out by means of crystallization from a solution-melt. Interaction in Cu₇SiS₅I – Ag₇SiS₅I system was investigated by means of differential-thermal analysis (Pt/PtRh thermocouple, heating speed 700 K/h), X-ray phase analysis (DRON 4-07, emission CuKα, angle scan step 2Θ – 0.02 deg, exposition – 0.5 s) and densimetric methods.
Results. According to the results of the X-ray phase analysis, calculations of the parameters of the elementary cell of Cu₇SiS₅I and Ag₇SiS₅I compounds and based on them alloys were carried out. The diffraction patterns of Cu₇SiS₅I and Ag₇SiS₅I compounds are indexed in face-centered cubic lattice F43m. The number and nature of the reflexes on the diffractograms of alloys containing 10–90 mol.% of Cu₇SiS₅I indicate that a continuous series of solid solutions is formed in the system. According to the results of differential-thermal analysis and X-ray phase analysis, a phase diagram of Cu₇SiS₅I – Ag₇SiS₅I system was constructed. It is characterized by the formation of unbounded α-solid solutions based on both compounds with a minimum on the liquidus curve (2nd type by Rozebom). The coordinates of the minimum point are 16 mol.% Cu₇SiS₅I, 1165 K. It is established that the compositional depenedences of the lattice parameter and density occur with a slight deviation "upward" from the from linear dependence.
Conclusions. The synthesis and growth of single crystals of (Cu_1-хAg_x)₇SiS₅I solid solutions were carried out. Alloys of Cu₇SiS₅I – Ag₇SiS₅I system were synthesized by means of direct one-temperature method from pre-synthesized Cu₇SiS₅I and Ag₇SiS₅I compounds. Growth of single crystals of (Cu_1-хAg_x)₇SiS₅I solid solutions was performed by means of crystallization from a solution-melt. Interaction in Cu₇SiS₅I – Ag₇SiS₅I system was investigated by means of differential-thermal analysis, X-ray phase analysis and densimetric methods. The diffraction patterns of Cu₇SiS₅I and Ag₇SiS₅I compounds were indexed in face-centered cubic lattice F43m. According to the results of X-ray diffraction studies, it was found that a continuous series of solid solutions is formed in Cu₇SiS₅I – Ag₇SiS₅I system. The phase diagram of Cu₇SiS₅I – Ag₇SiS₅I system is characterized by the formation of unbounded α-solid solutions based on both compounds with a minimum on the liquidus curve (2nd type by Rozebom) with the coordinates of the minimum point constituting 16 mol.% Cu₇SiS₅I, 1165 K. It is shown that the concentration changes of the lattice parameter and density observed with a slight deviation "upward" from the linear dependence

Keywords: solid solutions, synthesis, growth, difrfactogram, phase diagram, lattice parameter

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