A ceramic sample of La2Mo1.9Al0.1O9-α was prepared by a high-temperature solid-state reaction. The XRD pattern shows that the sample is of a single cubic phase of La2Mo2O9, indicating that the phase transition in La2Mo2O9 is completely suppressed by doping Al3＋with 5% at Mo6＋sites. The ion conduction properties of the ceramic sample have been studied by impedance spectra, oxygen concentration cell, oxygen pump (electrochemical oxygen permeation) techniques in the temperature range of 600～1000 ℃. The observed electromotive ferces(EMFs) of the oxygen concentration cell are in good agreement with the theoretical values and the ion transport number is unity, indicating that the ceramic sample is a pure ion conductor in the oxygen atmosphere at the studied temperatures. The experimental results of the discharge of the oxygen concentration cell and electrochemical oxygen permeation (oxygen pump) confirmed that the ceramic sample was a pure oxygen-ion conductor under oxygen atmosphere. The oxygen-ion conductivity at 1000 ℃ reached 0.12 S• cm－1, obviously higher than that of La2Mo2O9-α and La2Mo1.9Ga0.1O9-α under the same conditions.

Key words: La2Mo1.9Al0.1O9-α, La2Mo2O9, oxygen-ion conductor, ac impedance spectroscopy, oxygen concentration cell, oxygen pump