TRIANGULATION OF THE Cu-Sn-Se SYSTEM

Abstract

Copper-containing compounds exhibit a wide range of properties, including thermoelectric, photoelectric, optical magnetic, superionic, superconducting, etc., which determines the areas of their practical use. In recent years, studies of complex copper selenides as promising thermoelectric (TE) materials have been actively carried out due to their advantages over traditional TE materials. Like binary Cu2Se, ternary selenides have low phonon thermal conductivity and high electrical conductivity and thermoelectric quality factor. Typically, copper-containing compounds belong to the p-type conductors and crystallize in four main structural types, among which phases with a diamond-like structure should be distinguished. Data on the nature of physicochemical interaction in the Cu – Sn – Se system are limited and contradictory. In view of this, it is important to carry out the triangulation of the ternary system Cu–Sn–Se, which is the first stage of the study of multicomponent systems.
 The investigated alloys of the Cu – Sn – Se system were obtained by fusing elementary components of high purity in vacuum quartz ampoules. The obtained alloys were investigated using X-ray powder diffraction (XRD) and differential thermal (DTA) analyzes. At the temperature of homogenizing annealing (170 ° С) there are seven binary Cu2Se, CuSe, CuSe2, Cu6Sn5, Cu3Sn, SnSe, SnSe2 and one ternary phase Cu2SnSe3 stable in the Cu – Sn – Se ternary system. The existence of the ternary phase of Cu2SnSe4 has not been confirmed, because the alloy corresponding to its stoichiometric composition is a mixture of Cu2SnSe3 and Se. To establish quasibinary sections of the Cu – Sn – Se system were performed the synthesis and phase analysis of only the significant points in the most informative areas. This ensures the establishment of the nature of the maximum number of quasibinary sections with a minimum number of syntheses. According to the results of phase analysis in combination with the literature data the triangulation of the Cu – Sn – Se system was carried out at 170 ° С. The quasibinarity of the Cu2Se – SnSe, Cu2Se – SnSe2, Cu2SnSe3 – Se, Cu2SnSe3 – SnSe, Cu6Sn5 – SnSe, Cu3Sn – SnSe, and Cu3Sn – Cu2Se sections was confirmed, and the quasibinarity of the Cu3Sn – Cu2Se was established at first.
 Keywords: triangulation; quasibinary section; phase analysis.