PHASE DIAGRAMS OF THE С2ІІІX3 – DIVX2 SYSTEMS (СІІІ – AS, SB, BI; DIV – GE, SN; X – S, SE)

Abstract

The results of experimental studies of phase diagrams of quasi-binary systems of the С2ІІІX3 – DIVX2 type are presented where СІІІ – As, Sb, Bi; DIV – Ge, Sn; X – S, Se. The samples were synthesized by direct co-melting of high-purity elements in evacuated ampoules; the maximum temperature was 1170 K. Themethods of powder X-ray diffraction and differential thermal analysis were used to identify the phases, determine the composition and nature of phase transitions. Investigated phase diagrams are characterized by different types of invariant processes, either peritecticor eutectic. The sulfide system As2S3 – GeS2 features peritectic interaction at 722 K with limited mutual solubility of the components in the solid state; a eutectic type of interaction was observed in the similar selenium-containing system As2Sе3 – GeSе2 (618 K, 20 mol.% GeSе2). The Sb2S3 – GeS2 system features eutectic type of interaction with the eutectic point at 747 K and 35 mol.% GeS2; glassy and glass-crystalline phases were observed in the intermediate range of compositions, which indicates a tendency to glass formation. The selenide system Sb2Se3 – GeSe2 similarly exhibits eutectic interaction with the eutectic point coordinates of 757 K, 58 mol.% GeSe2, absent of solid solutions and glassy state. The Bi2S3 – GeS2 section is also of the eutectic type (860 K; 52 mol.% GeS2) with the formation of solid solution ranges of the initial components. The systems involving tin (IV) sulfide and selenide exhibit eutectic: As2Se3 – SnSe2 (640 K, 19 mol.% SnSe2), Sb2S3 – SnS2 (737 K, 65 mol.% Sb2S3), Sb2Se3 – SnSe2 (773 K, 50 mol.% SnSe2), Bi2S3 – SnS2 (938 K, 42 mol.% SnS2), Bi2Se3 – SnSe2 (831 K, 67 mol.% SnSe2) and peritectic: As2S3 – SnS2 (727 K) types of interactions. The Sb2S3 – SnS2 system features the ternary phase Sb2SnS5 which is formed by the peritectic reaction L + SnS2 ↔ Sb2SnS5 at 765 K, while no ternary phases were found in selenide systems, indicating the effect of chemical bonding and structural factors on the stability of the phases. Additionally, eutectoid and peritectoid transformations associated with the phase transitions of GeS2 and SnS2 were recorded in some systems. Obtained results are important for further research into the quasi-ternary systems based on these binary compounds and the development of materials with controlled properties for electronics, photonics, and energy production.