Pure and dense La2Mo2O9 ceramic electrolytes with grain sizes of 1-3 mu m were fabricated from nanocrystalline powders by a novel three-stage, one-cycle, pressureless thermal processing method at temperatures as low as 600 degrees C. Phase formation, microstructure and grain size of the samples were examined using X-ray diffraction and scanning electron microscopy. Density of the sintered samples was determined as in the range of 94-96% of the theoretical density by weight/geometric measurements. Impedance spectroscopy was used to characterize the electrical properties of the sintered samples. The conductivity of the three-stage sintered samples reaches a value of 0.018 S/cm at 600 degrees C and 0.05 S/cm at 700 degrees C, much higher than that of the samples fabricated by conventional solid-state reaction method, but similar to that of the samples sintered at 950 degrees C for 12 h from the same nanocrystalline powders. The high conductivity of these samples was attributed to the co-operation of the excellent performance of nanocrystalline powders and the advantages of the novel three-stage low-temperature thermal processing. (c) 2006 Elsevier B.V. All rights reserved.