Open AccessINTERACTION IN THE Ag6PS5I–Ag7GeS5I AND Ag7GeS5I–Ag7SiS5I SYSTEMS
Author(s) -
А.І. Погодін,
M.J. Filep,
Iryna Shender,
О.П. Кохан,
І. П. Студеняк
Publication year - 2021
Publication title -
naukovij vìsnik užgorodsʹkogo unìversitetu. serìâ hìmìâ
Language(s) - English
Resource type - Journals
ISSN - 2414-0260
DOI - 10.24144/2414-0260.2021.1.42-46
Subject(s) - ternary operation , crystal structure , crystallography , solid solution , valence (chemistry) , chemistry , crystal chemistry , liquidus , materials science , inorganic chemistry , phase (matter) , organic chemistry , computer science , programming language
Argyrodites are a wide class of tetrahedrally close–packed ternary and quaternary compounds that have a large number of representatives. Argyrodite family compounds always include two types of cations: univalent (type A) and multivalent (type B). B type multivalent cations (3–5) are tetrahedrally coordinated by anions and form a rigid anionic framework, and the univalent A type cations are located in the cavities between them and have different occupancy of crystallographic positions (disordered sublattice). The most common are argyrodites based on four and five valence p–elements. Type A and B cations are subject to isomorphic substitution, which in combination with the proximity of the crystal lattice parameters causes a significant number of solid solutions between the compounds with the structure of argyrodite. These solid solutions are formed by both isovalent and heterovalent substitution, which is used to optimize the functional parameters of the studied materials. Argyrodite structure compounds can be used as optical, superionic, and thermoelectric materials. This work aims to study the physico–chemical interaction at isovalent Si4+↔Ge4+and heterovalent substitution of P5+↔Ge4+ within the Ag7SiS5I–Ag7GeS5I and Ag6PS5I–Ag7GeS5I systems. Several alloys in the Ag6PS5I–Ag7GeS5I and Ag7SiS5I – Ag7GeS5I systems were synthesized by a direct single–temperature method using the pre–synthesized quaternary argyrodites. The obtained samples were investigated by the methods of differential thermal (DTA), X–ray diffraction (XRD), and microstructural (MSA) analyses. Based on the obtained results, it was found that the Ag6PS5I–Ag7GeS5I section is partly quasi–binary due to the incongruent melting of Ag6PS5I. The liquidus of the system is formed by lines of primary crystallization of Ag2S and Ag7GeS5I crystals, which intersect at the point with coordinates: 6 mol. % Ag7GeS5I, 1009 K. The subsolidus part of the Ag6PS5I–Ag7GeS5I system is characterized by the formation of a continuous series of solid solutions. The phase diagram of the Ag7SiS5I–Ag7GeS5I system is characterized by unlimited solubility of components in liquid and solid phases. In the Ag6PS5I–Ag7GeS5I system a positive deviation from Vegard's law is observed.