Synthesis, growth and structural investigation of Сu<sub>7</sub>SiS<sub>5</sub>I, Ag<sub>7</sub>SiS<sub>5</sub>I single crystals and solid solutions on their base

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-х Ag x ) 7 SiS 5 I solid solutions. Methods. Alloys of Cu 7 SiS 5 I – Ag 7 SiS 5 I system were synthesized by means of direct one-temperature method from pre-synthesized Cu 7 SiS 5 I and Ag 7 SiS 5 I compounds. Growth of single crystals of (Cu 1-х Ag x ) 7 SiS 5 I solid solutions was carried out by means of crystallization from a solution-melt. Interaction in Cu 7 SiS 5 I – Ag 7 SiS 5 I 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 Cu 7 SiS 5 I and Ag 7 SiS 5 I compounds and based on them alloys were carried out. The diffraction patterns of Cu 7 SiS 5 I and Ag 7 SiS 5 I compounds are indexed in face-centered cubic lattice . The number and nature of the reflexes on the diffractograms of alloys containing 10-90 mol.% of Cu 7 SiS 5 I 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 Cu 7 SiS 5 I - Ag 7 SiS 5 I system was constructed. It is characterized by the formation of unbounded a-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.% Cu 7 SiS 5 I, 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-х Ag x ) 7 SiS 5 I solid solutions were carried out. Alloys of Cu 7 SiS 5 I – Ag 7 SiS 5 I system were synthesized by means of direct one-temperature method from pre-synthesized Cu 7 SiS 5 I and Ag 7 SiS 5 I compounds. Growth of single crystals of (Cu 1-х Ag x ) 7 SiS 5 I solid solutions was performed by means of crystallization from a solution-melt. Interaction in Cu 7 SiS 5 I – Ag 7 SiS 5 I system was investigated by means of differential-thermal analysis, X-ray phase analysis and densimetric methods. The diffraction patterns of Cu 7 SiS 5 I and Ag 7 SiS 5 I compounds were indexed in face-centered cubic lattice . According to the results of X-ray diffraction studies, it was found that a continuous series of solid solutions is formed in Cu 7 SiS 5 I – Ag 7 SiS 5 I system. The phase diagram of Cu 7 SiS 5 I - Ag 7 SiS 5 I system is characterized by the formation of unbounded a-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.% Cu 7 SiS 5 I, 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.