Research Status of the Novel La_2Mo_2O_9-based Oxide-ion Conductors

La_2Mo_2O_9-based oxide-ion conductors have attracted more and more attention since they were reported having high ionic conductivity in 2000 by Lacorre et. al. In this paper the recent investigation on the novel La2Mo2O9-based oxide-ion conductors is reviewed. It is focused on the structure and phase transition, oxide-ion conductivity, mechanism of oxygen vacancy diffusion, chemical stability, and thermal expansion coefficient in the pure and doped La2Mo2O9 samples. It is pointed out that the La2Mo2O9-based oxide-ion conductors could be possibly applied in the field such as solid oxide fuel cells, oxygen sensors, oxygen permeable membrane.