The phase equilibria in the 2Cu₂S + GeSe₂ ↔ 2Cu2Se +GeS₂ reciprocal system were experimentally investigated by means of differential thermal analysis (DTA) and powder X-ray diffraction (PXRD) technique as well as electromotive force measurements (EMF) of concentration chains with Cu₄RbCl₃I₂ solid electrolyte. Five isopleth sections Cu₈GeS₆-Cu₈GeSe₆, Cu₈GeSe₆-Cu₂Se, Cu₂GeS₃-Cu₈GeSe₆, Cu₂S-GeSe₂ and Cu₂Se-GeS₂ and four isothermal sections at 300, 800, 1100 and 1200 K as well as liquidus surface projection of the system were constructed based on the experimental data. The systemwas found to be mutually reciprocal with the formation of continuous or wide areas of solid solutions series along the Cu₂S-Cu₂Se, Cu₂GeS₃-Cu₂GeSе₃, Cu₈GeS₆-Cu₈GeSe₆ and GeS₂-GeSe₂ binary systems. The partial molar thermodynamic functions of the copper for the Cu₈GeS₆-xSex (where x ј 0.6; 1.2; 1.8; 2.4; 3.6; 4.8; 5.4 and 5.7) solid solutions were calculated based on the EMF measurements data.

“Study of the 2Cu₂S + GeSe₂ ↔ 4 2Cu₂Se + GeS₂ reciprocal system and thermodynamic properties of the Cu₈GeS₆__xSe_x solid solutions” Isfandiyar J. Alverdiyev,  Ziya S. Aliev, Sara M. Bagheri, Leyla F. Mashadiyeva, Yusif A. Yusibov, Mahammad B. Babanly. Journal of Alloys and Compounds 691 (2017) 255-262.