A new series of nanocrystalline La2-xPrxMo2O9 (0.2 <= x <= 0.8) powders are synthesized through the pyrolysis of polyacrylate salt precursors prepared via in situ polymerization of the metal salts and acrylic acid. The polymeric precursors are characterized by thermogravimetric and differential thermal analysis (TG/DTA) to determine the thermal decomposition and crystallization temperature, which is found to be at 510 degrees C. X-ray diffraction analysis indicates that the substitution of La by Pr preserves the single-phase La2Mo2O9 structure up to a Pr dopant concentration of x <= 0.7. The particle size and the alpha -> beta phase transition of the Pr-doped La2Mo2O9 samples are studied by using a transmission electron microscope (TEM) and differential scanning calorimetry (DSC), respectively. The sintering behaviour of the Pr-doped samples are examined via isothermal and non-isothermal experiments. It demonstrates that the synthesized nanocrystalline powders have good sinterabilty and a relatively low sintering temperature of 800 degrees C for 4 h is sufficient to reach similar to 99% of the theoretical density with good microstructures. Furthermore, the oxide-ion conductivity increases with increasing Pr content and the maximum conductivity is attained at x = 0.5 in La2-xPrxMo2O9. (c) 2007 Published by Elsevier B.V.