Formation, Structure, and Decomposition of Lanthanide Basic Carbonates

Precipitation, crystal structure, and thermal decomposition behavior of the rare-earth basic carbonates were investigated. Precipitates were produced from hydrolysis of rare-earth cations in hot urea solutions. The light rare earths formed were crystalline with regular geometric shapes, whereas heavy rare earths produced amorphous, spherical monodisperse particles. Crystalline phases belong to ancylite-type orthorhombic symmetry. Unit-cell volume was related to interatomic distance. Thermal decomposition of the crystalline precipitates occurred in two major distinct steps to produce oxide, whereas heavy rare earths decomposed continuously with several distinct effects to produce oxide powder.