Powders of oxide-ion conductor La 2 Mo 2 O 9 presenting nanodomains were synthesized by using polyol processes. The influence of different process parameters on the structure and particles morphology was determined. By the classical polyol process, whatever the polyol solvent used (ethylene glycol, diethylene glycol, 1,2-propanediol and tetraethylene glycol) platelet particles with dimensions of few hundred nanometers long and around twenty nanometers thick were observed, as agglomerates of small subparticles. Only with diethylene glycol, pure La 2 Mo 2 O 9 was obtained, whereas with microwave assistance, ethylene glycol also leads to pure product. For both ethylene and diethylene glycol solvent, the microwave assisted process resulted in either agglomerates or desert roses conglomerates after heat treatment at 500°C for 5 min or 2h, respectively. Specific surface areas, ranging between 23 and 36 m².g-1 , have been measured for pure La 2 Mo 2 O 9 powders.

La 2 Mo 2 O 9 nanostructured powders were synthesized by the polyol process. The effects of the nature of the polyol, the refluxing time, the hydrolysis ratio, the metal concentration and the addition of hydroxyde ions, on the purity and morphology of the powders are determined. Two main morphologies are observed, the particles being in the shape of platelets or spheres, with respectively diethylene glycol or ethylene glycol as solvent. A specific surface area of 24 m².g-1 was reached by varying the metal concentration. The conductivity measurements were recorded on pellets that present in some cases a closed porosity, the relative density reaching 95% without any milling step. According to the synthesis parameters, the grain conductivity can be slightly increased, the total conductivity remaining only slightly lower than that of pellets made of powders synthesized by solid state reaction.