Phase relationships in the 1.5GeS2 + Cu2GeSe3 ↔ 1.5GeSe2 + Cu2GeS3 reciprocal system

The phase relations in the 1.5GeS2 + Cu2GeSe3 ↔ 1.5GeSe2 + Cu2GeS3 system have been investigated over the entire concentration range mainly by thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques, with the aid of microhardness and electro-motive force measurements (EMF) applied to equilibrated alloys. The liquidus surface projection, isothermal section at 800 K and the phase diagrams of the two vertical sections have been constructed. The homogeneity ranges and primary crystallization fields of phases as well as the character and temperature of non- and monovariant equilibria were determined in the system. It was found that the system is reciprocally reversible and is featured by continuous solid solubility fields along the boundary GeS2-GeSe2 and Cu2GeS3-Cu2GeSе3 systems. The partial molar thermodynamic functions (ΔG‾,ΔH‾,ΔS‾) of copper were calculated for the Cu2GeS3−xSex (for x = 0.6; 1.2; 1.8; 2.4) solid solutions based on the results of the EMF measurements.