Gd-doped ceria particles with nanometer size were prepared by spray pyrolysis from spray solution containing ethylene glycol. The effect of ethylene glycol and gadolinium dopant on the morphology of the ceria particles prepared by spray pyrolysis was investigated. The Gd-doped ceria particles prepared from pure aqueous solution had submicron size, spherical shape and dense structure after post-treatment. The Gd-doped ceria particles prepared from solution containing ethylene glycol had loosely aggregated structure of the primary particles with nanometer size after post-treatment at 900 and 1050 degrees C. The Gd-doped ceria particles had more loosely aggregated and regular morphology than the pure ceria particles at the post-treatment temperature of 900 degrees C. The gadolinium component used as dopant suppressed grain growth in ceria particles prepared by spray pyrolysis. Nanometer size Gd-doped ceria particles were prepared by a ball milling process of the particles obtained by spray pyrolysis. The mean size of the Gd-doped ceria particles was 46 nm after a post-treatment at 1050 degrees C. The ionic conductivity of the Gd-doped ceria particles prepared by spray pyrolysis was compared with that of the commercial yttria-stabilized zirconia (YSZ). (c) 2005 Elsevier B.V. All rights reserved.