PHASE-DIAGRAM OF SRO-CAO-CUO TERNARY-SYSTEM

The phase diagrams of SrOCuO, SrOCaO and CaOCuO binary systems, the room temperature section of SrOCaOCuO ternary system, vertical section of Sr2CuO3Ca2CuO3 system and crystallographic parameters of compounds in SrOCaOCuO system are investigated by X-ray powder diffraction and thermal analysis. There sre three binary compounds: Sr2CuO3, SrCuO2 and Sr3Cu5O8 in SrOCuO system. They are all formed by peritectic reactions and all of them belong to orthorhombic lattice. The space group of Sr2CuO3 is Immm with lattice parameters: a = 1.2708 nm, b = 0.3913 nm, c = 0.3502 nm. The space group of SrCuO2 is Cmcm with lattice parameters: a = 0.3573 nm, b = 1.6333 nm, c = 0.3915 nm. Sr3Cu5O8 has a face-centre lattice with parameters: a = 1.3402 nm, b = 1.1470 nm, c = 0.3939 nm. In CaOCuO system only one compound Ca2CuO3 is observed. Ca2CuO3 is isostructural with Sr2CuO3. Its lattice parameters are a = 1.2243 nm, b = 0.3779 nm, c = 0.3258 nm. The continous solid solution is formed in the CaOSrO system. The section at room temperature in SrOCaOCuO system can be divided into four two-phase regions and two three-phase regions. Solid solutions of Sr2(1-x)Ca2xCuO3 (x = 0 to 1), Sr1-xCaxCuO2 (x ≤ 0.65) and Sr3(1-x)Ca3xCu5O8 (x ≤ 0.50) are formed. The lattice parameters of solid solutions decrease with increasing Ca-contents. © 1990.