Cerium Compounds Prepared by Homogeneous Precipitation Methods

抄録

Cerium compounds were prepared from aqueous solution of cerium nitrate by homogeneous precipitation methods. Urea and hexamethylenetetramine (HMT) were used as chemicals that produce NH₃ and consequently NH₄OH when heated to about 80^oC in aqueous solution. When urea was used, the precipitates with uniform in size, larger than 1 μm, were obtained. However, the products were not oxide. They were confirmed by x-ray diffraction to be cerium oxide carbonate hydrate. When HMT was used, the precipitates were very fine in size, less than 0.1 μm and they were cerium oxide. These products were compared with the precipitates which formed when NH₄OH was directly used. These products were also sintered to find the effect of preparation method on the density of bulk sample. CeO₂ prepared by HMT exhibited the highest sintered density.