Phase Relations in La2O3—Gd2O3—CuO System at 950 °C.

Abstract 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 °C is presented. The system is characterised with solid solutions of several well-known binary compounds such as T–La2CuO4 (orthorhombic at 950 °C), tetragonal T′–Gd2CuO4, and monoclinic La2Cu2O7 (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 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.