Abstract: La₂Ni_1-yCo_yO_4+δ(y=0—0.2) fine powders were synthesized by a polyaminocarboxylate complex method, and the structure and mixed conducting properties of the resulting ceramics were investigated. X-ray diffraction Rietveld refinement results indicate that La₂Ni_1-yCo_yO_4+δ compositions have an orthorhombic structure with Fmmm space group. The substitution of partial La³⁺ with Co at the B-site caused an increase in the length of Ni/Co—O₁ bond in the ab plane and La/Sr—O₂ bond along c axis. Moreover, it was detected that the oxygen nonstoichiometry(δ) became larger with increasing Co content. The cobalt substitution resulted in a shift of the temperature for the electrical conductivity maximum to higher temperature direction and a decline of electrical conductivity together with a modification of oxygen ionic conducting properties. The effect of cobalt substitution on the mixed conducting properties of La₂NiO_4+δ ceramic can be interpreted with respect to the variation in crystal structure parameters.

Key words: La₂Ni_1-yCo_yO_4+δ, Polyaminocarboxylate complex method, Structure, Conductivity