CRYSTAL GROWTH OF Ag7PS6 BY DIRECTIONAL CRYSTALLIZATION METHOD

Abstract

Argyrodites are a class of compounds united by a similar structural motif. Typical for argyrodites is the coexistence of rigid anionic and disordered cationic sublattices. Due to this, argyrodites exhibit a wide range of properties. This work is devoted to the development of the single crystal growth regime of high-quality single-crystalline samples of Ag7PS6, which belongs to the compounds with argyrodite structure. The initial Ag7PS6 alloy is obtained from high purity elementary components by a two-step and one-temperature method. The maximum synthesis temperature was 850°C. The obtained alloy was investigated by DTA and XRD methods. The congruent melting of Ag7PS6 (Tmelt = 801°C) and the structural phase transition P213 → F-43m at a temperature of 271°C was confirmed. The study of the phase composition established the synthesized alloy is single-phase. The growth of Ag7PS6 was carried out by the directional crystallization method from the melt. The growth regime of Ag7PS6 was selected taking into account the nature of the thermal behavior of the compound based on DTA data. As a result, the grown Ag7PS6 single crystal of ~ 40 mm long and 12 mm in diameter was obtained. According to the results of XRD, it has been established that the grown Ag7PS6 single crystal is single-phase and crystallizes in a primitive cubic cell with lattice parameters of 10.3917 Å.