Cerium (IV) oxide synthesis and sinterable powders prepared by the polymeric organic complex solution method

Three processing methods making use of different cations complexant as citric acid (CA), polyvinylalcohol (PVA) or polyethylene glycol (PEG) have been used to prepare high purity fine CeO2 powder with different particle size and agglomeration degrees. Green compacts prepared from the differently agglomerated powders were studied by Hg-porosimetry, and pore-size distribution curves were taken to compare the uniformity of the green compacts microstructure. The citrate-based prepared powders could be sintered to densities of 98% of theoretical at 1250 °C for 10 h, and to nearly fully dense (99.5% theoretical) at 1380 °C for 1 h. Otherwise, sintering temperatures of 1380 °C and ⩾1650 °C were necessary to obtain densities of ≈98% theoretical when using PEG and PVA as complexant, respectively. The different shrinkage-rate behavior was assumed to be closely related to differences in the pore-size distribution in the green compacts. Pore-size evolution was taken into account to study the microstructural development during sintering. Moderate grain growth (grain size ≈200 nm) was observed until densities lower than about 90% theoretical, while it considerably increases for higher densities. Grain size and microstructure uniformity could be related to the green compacts uniformity, i.e. the pore-size distribution and the agglomeration degree.