Precipitation and Coprecipitation Method

Chemical precipitation is a widely used method for synthesizing solid materials from solution. This method utilizes a liquid-phase reaction to prepare insoluble compounds that are crystalline or amorphous precipitates. The precipitate usually is composed of fine particles, and, of course, ceria-based fine particles can be synthesized by this method. Usually, ceria preparation is carried out by calcination of the hydroxide or oxalate gel precipitated using the reaction of aqueous solution of inorganic cerium salt (CefNOjIj, CeClj, CeS04, and (NH4)2Ce(N03)6) with alkali solution (NaOH, NH4OH, and (NHj)2-H20) or oxalic acid.  

Another process to obtain uniform fine ceria particles is the forced hydrolysis method that is useful for preparation of metal oxides and hydroxides. 

In the synthesis of mixed oxides, the co-precipitation method is the most commonly used wet-chemical process. Salts of the several metals are dissolved in the same solvent (water is the most popular one). Ideally, a quantitative and simultaneous precipitation of all the cations occurs without segregation of any particular constituents in the precipitates. This ideal situation is very rare in most cases, especially more than two metal cations are involved. Differences in solubility between several precipitating phases affect the precipitation kinetics of each metal 

Sample Starting materials Precipitant Calcination temp. / K Average size / nm BET /m g Ref.. 

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