Mesoporous and nanocrystalline CeO2, ZrO2 and CeO2-ZrO2 catalysts were prepared by impregnating the corresponding metal solutions on sawdust. Subsequently, carbonization and calcinations of carbon composites were performed in two oxidizing conditions: LM - low calcination temperature and mild oxidation atmosphere and HS - high calcination temperature and severe oxidation atmosphere. The catalyst were well characterized by thermogravimetry (TG), BET surface area, pore size distribution (PSD), particle size analysis, powder X-ray diffraction, and high-resolution transmission electron microscopy (HRTEM) coupled with energy-dispersive (EDS) analysis. Thus the effects of calcination temperature and atmosphere on the growth of particle/crystalline size of the corresponding metal oxides could be understood. Powder X-ray diffraction studies reveal that the Ce, Zr and Ce-Zr are amorphous in carbon composite and after the calcination; the characteristic peaks of their oxides were observed. The particle size distributions showed that the mild oxidation conditions have provided the narrow size distribution of particles at 100 mum than 10 mum, which were calcined at 700 degreesC. Physicochemical characterization studies including HRTEM analysis of the representative samples show the presence of particle size of CeO2 with 5-10 nm, ZrO2 with 5-10 nm and Ce0.5Zr0.5O2 is in the range of 5-10 nm. EDS analysis confirmed that they are in cubic phase. (C) 2004 Elsevier B.V. All rights reserved.