Phase relations in La 2O 3–Gd 2O 3–CuO system at 950 °C

Abstract

Phase equilibria in La 2O 3–Gd 2O 3–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 °C is presented. The system is characterised with solid solutions of several well-known binary compounds such as T–La 2CuO 4 (orthorhombic at 950 °C), tetragonal T′–Gd 2CuO 4, and monoclinic La 2Cu 2O 7 (α-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 La 2O 3 and Gd 2O 3 (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.