Gel-Combustion Synthesis of Nanocrystalline Cerium Oxide and Its Powder Characteristics

Nanocrystalline ceria powders were prepared by using citrate gel combustion. The influence of the composition of the combustion mixture on the characteristics of the final product was investigated. Ceria powders obtained by calcining the combustion residue in air at 1073 K were characterized for their specific surface area (SSA), X-ray crystallite size (XCS), bulk density (BD), particle size distribution (PSD) and residual carbon. The dependence of these properties on the fuel to oxidant ratio (R) of the initial mixture was investigated. The microstructure of the calcined ceria powders prepared from a mixture with R = 0.25 was investigated by using high resolution transmission electron microscopy. All the calcined powders were pelletised and sintered at 1473, 1673 and 1873 K, and their sinterability was compared by measuring the density of the sintered pellets. A maximum sintered density of 98 % theoretical density could be achieved at a temperature as low as 1473 K for the first time for the powder prepared from a mixture with R = 0.75. The systematic dependence of the properties of these powders on the composition of the initial mixture is being reported for the first time. Powders obtained from a mixture with an R value 0.25 showed a linear increase in sintered densities with the sintering temperature. Other powders exhibited anomalous decrease in the sintered density at high temperature, probably due to irregular grain growth coarsening.