INTERACTION IN THE SYSTEMS Tl2Se–Ga(In)2Se3–SnSe2

Abstract

Quasi-ternary systems Tl2Se–Ga(In)2Se3–SnSe2 were investigated by physico-chemical analysis methods (differential thermal, X-ray phase, X-ray structural analysis), and their isothermal sections at 520 K in the entire concentration range were plotted. On the section of TlGaSe2–SnSe2 the existence of three compounds Tl2Ga2SnSe6, TlGaSnSe4, and TlGaSn2Se6, was found. The quaternary compounds form in the peritectic reactions L+α↔Tl2Ga2SnSе6 at 956 K, L+Tl3Ga3SnSе8↔Tl- GaSnSе4 at 851 K, and L+SnSе2↔TlGaSn2Sе6 at 833 K. The crystal structure of Tl2Ga2SnSe6 was determined in the tetragonal symmetry, S.G. I4/mcm; а=08095(1), c=0.402(1) nm), TlGaSn2Se6 has trigonal structure (S.G. R3; a=1.03289, c=0.94340 nm). The isothermal section of the Tl2Se–Ga2Se3–SnSe2 system at 520 K contains 9 single-phase fields and 14 regions of two-phase equilibria which separate the concentration triangle into 10 fields of three-phase equilibria. The largest solid solutions ranges are those of the TlGaSе2 and Ga2Se3 compounds. The location of 5 three-phase fields and 11 two-phase equilibria between binary and ternary compounds were identified at the section of the Tl2Se–In2Se3–SnSe2 system at 520 K. Phase diagram of the TlInSe2–SnSe2 section of the eutectic type. The solid solubility range of TlInSe2 along this section reaches 28 mol.%. Single crystals of the solid solutions Tl1‑xGa1‑xSnxSe2 (x=0.05–0.1) and Tl1‑xIn1‑xSnxSе2 (x=0–0.25) that form in the TlGa(In)Se2–SnSe2 systems were grown by the Bridgman-Stockbarger method. According to X-ray diffraction analysis results, it was determined that the grown Tl1-xGa1-xSnxSe2 crystals have monoclinic structure (S.G. C2/c), and the Tl1‑xIn1-xSnx- Sе2 crystals are tetragonal (S.G. I4/mсm).