The Cu₂S–GeS₂–P₂S₅ system

Chem. Met. Alloys 16 (2023) 43-51

Orysia BEREZNYUK, Oleksandr SMITIUKH, Lyubomyr GULAY, Iryna PETRUS’, Lyudmyla PISKACH

https://doi.org/10.30970/cma16.0433

The isothermal section of the Cu₂S–GeS₂–P₂S₅ system at 500 K was investigated. The phase interactions in the system are characterized by the formation of considerable solid solution ranges of Cu₂S, Cu₇PS₆, Cu₃PS₄, Cu₈GeS₆, and Cu₂GeS₃. According to the results of differential thermal analysis and X-ray diffraction, the phase diagrams of the Cu₈GeS₆–Cu₇PS₆ and Cu₂GeS₃–Cu₃PS₄ sections at 300 K feature extended solid solution ranges. In the former section, they range up to 30 mol.% based on the LT-Cu₇PS₆ modification (SG P2₁3), and 10–32 mol.% Cu₇PS₆ between the HT modifications of the argyrodite compounds (SG F-43m). The solid solution range of Cu₃PS₄ (SG Pmn2₁) extends up to 45 mol.%, and that of Cu₂GeS₃ (SG Сс) slightly over 10 mol.%. However, the systems are not quasi-binary in the entire temperature range due to the peritectic character of melting of Cu₈GeS₆ and Cu₃PS₄. The phase diagram of the quasi-binary system Cu₂S–GeS₂ was re-investigated by differential thermal analysis and X-ray diffraction. The incongruent nature of the melting of Cu₄GeS₄ at 1209 K was established.

Isothermal section of the Cu₂S–GeS₂–P₂S₅ system at 500 K.

Keywords

Solid solution / Crystal structure / Phase diagram / Isothermal section / X-ray diffraction