Research progress of La2Mo2O9-based oxide-ion conductor electrolyte materials

Recently, solid oxide-ion conductors have been received considerable attention owing to their potential applications in solid oxide fuel cells, oxygen sensor, etc. An innovative solid oxide-ion conductor, Lanthanum-molybdenum oxide (La2Mo2O9), presents a reversible phase transformation around 580°C from a low-temperature form ɑ-La2Mo2O9 to a high-temperature form β-La2Mo2O9, leading to varying the ionic conductivity. This paper reviews the research progress of La2Mo2O9 and its doping systems, the structure and phase transition of the material, the conductivity of oxide-ion, ionic conductivity, and chemical stability of the material in reducing atmosphere and high temperature are discussed. The research progress of La2Mo2O9 electrolyte was reviewed from four aspects: structure, conduction mechanism, preparation method, conductivity and future prospect.