Nanostructured cerium oxide: preparation and properties of weakly-agglomerated powders

Nanocrystalline powders of cerium oxide were prepared from cerium(III) nitrate solution by a two-stage precipitation process which yielded weakly-agglomerated powders with a crystallite size smaller than 5 nm. Hydrogen peroxide was added to cerium nitrate at 5°C to slowly oxidise Ce3+ to Ce4+ and thereby initiate homogeneous precipitation with the formation of dense spherical agglomerates. The precipitation process was completed by the addition of ammonium hydroxide which disrupted the spherical agglomerates leaving a weakly-agglomerated power of hydrated ceria. The process was completed by hydrothermal treatment at 180°C without increase in crystallite size. The powders were characterised by X-ray diffraction, transmission electron microscopy and thermogravimetric analysis. The weakly-agglomerated state of the powder and the uniform crystallite size of under 5 nm are favourable characteristics for many applications.