Phase relations in La2O3-Gd2O3-CuO system at 950 deg C

Phase equilibria in La2O3-Gd2O3-CuO system were studied based on samples obtained from appropriate mixtures of the starting components, prepared in air by a conventional solid state reaction. The phase relations prevalent in this system have been deduced based on X-ray diffraction patterns of well-equilibrated samples. An isothermal cross-section diagram through the system at 950 deg C is presented. The system is characterised with solid solutions of several well-known binary compounds such as T-La2CuO4 (orthorhombic at 950 deg C), tetragonal T'-Gd2CuO4, and monoclinic La2Cu2O7 (alpha-solid solution). The system contains also the T* -type three-component phase of tetragonal symmetry, intermediate to those of T and T. A large solubility domain has been found between La2O3 and Gd2O3 (B solid solution of monoclinic structure form typical for RE-sesquioxides), extending deeply towards the ternary system with CuO. Lattice parameters vs. chemical composition are presented for some of the phases found in this system.