An X-ray diffraction, dielectric relaxation and direct-current conductivity investigation was made of the influence of cationic (Al3+, Fe3+, Mn4+, Nb5+, V5+) substitutions at Mo sites upon the structure, O-ion diffusion and electrical properties of La2Mo2O9 oxide-ion conductors. Except in the case of V5+ substitution, none of the substitutions (of up to 5%) could suppress the phase transition in La2Mo2O9. In the case of dielectric measurements, one prominent relaxation peak was observed, both in the temperature spectrum and in the frequency spectrum, which was associated with the short-range diffusion of O vacancies. The activation energy for O-ion diffusion was deduced to be 1 to 1.1eV for Al-, Fe-, Mn- and Nb-doped samples and to 1.4 to 1.5eV for V-doped samples. All of the substituted samples had a higher conductivity than that of the undoped compound. In Al-, Fe-, Mn- and Nb-substituted materials, the phase transition was not suppressed. However, K-substitution at the La-site could completely suppress the transition and maintain a high conductivity at low temperatures.

Study on the Electrical Conductivity and Oxygen Diffusion of Oxide-Ion Conductors La2Mo2−xTxO9−δ (T = Al, Fe, Mn, Nb, V). C.Li, X.P.Wang, J.X.Wang, D.Li, Z.Zhuang, Q.F.Fang: Materials Research Bulletin, 2007, 42[6], 1077-84