Abstract
It has been successfully demonstrated that spherical lanthanum hydroxycarbonate colloids can be synthesized under proper hydrothermal conditions using urea as the precipitant. It is also shown that the particle morphology may be related to its compositions, which in turn depends upon the reaction conditions and the aging time. In the present reaction system, all spherical precipitates will eventually transform into crystalline and rodlike particles if they are aged for a long period.