Phase relations in La2O3-Gd2O3-CuO system at 950°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 degrees C is presented. The system is characterised with solid solutions of several well-known binary compounds such as T-La2CuO4 (orthorhombic at 950 degrees 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. (c) 2005 Elsevier B.V. All rights reserved.