Effect of microwave radiation on the formation of Ce2O(CO3)2•H2O in aqueous solution

Reaction between urea and cerium nitrate with/without microwave radiation was investigated. Decomposition of urea occurred in aqueous solution to form NH4OH when the solution was heated to approximately 80 degreesC. The decomposition products of urea in aqueous solution reacted with cerium nitrate to form cerium oxycarbonate hydrate powder (Ce2O(CO3)(2)(H2O)-H-.). When the aqueous solution was heated by hot plate to decompose urea, elongated powder of Ce2O(CO3)(2)(H2O)-H-. with an aspect ratio of approximately 3 was obtained. For the reaction in which the microwave radiation was used to heat the solution for only 5 min, the resulting Ce2O(CO3)(2)(H2O)-H-. powder was almost identical to the powder that was formed by hot plate heating. However, when the microwave radiation was used for 15 min, the precipitated powder was spherical in shape. These results indicate that the microwave radiation had an effect on the reaction in the aqueous solution. (C) 2002 Elsevier Science B.V All rights reserved.