Preparation of discrete nanosize ceria powder

Ultrafine CeO2 powders have been prepared from a solution of cerium(III) nitrate by a two-stage precipitation process. Precipitated cerium hydroxide gel was reacted in boiling basic solutions. Amorphous cerium hydroxide gel crystallized to CeO2·nH2O (n<2) during the low-temperature hydrothermal treatment, and this process was effective to dehydrate the adsorbed water and decrease the hydrogen bonding effect leaving a weakly agglomerated powder. The preparation was calcined at 600 °C to obtain urea. In order to avoid agglomerating during drying and calcining, sodium hexametaphosphate was introduced. The resulting powders are highly crystalline and weakly agglomerated.