Hydrothermal synthesis of single-crystal CeCO3OH and their thermal conversion to CeO2

Hexagonal single-crystalline cerium carbonate hydroxide (CeCO3OH) precursors with dendrite morphologies have been synthesized by a facile hydrothermal method at 180 ℃ using CeCl3·7H2O as the cerium source, triethylenetetramine as both an alkaline and carbon source, with triethylenetetramine also playing an important role in the formation of the dendrite structure. Polycrystalline ceria (CeO2) have been obtained by calcining the precursor at 500 ℃ for 4 h. The morphology of the precursor was partly maintained during the heating process. The optical absorption spectra indicate the CeO2 nano/microstructures have a direct band gap of 2.92 eV, which is lower than values of the bulk powder due to the quantum size effect. The high absorption in the UV region for CeO2 nano/microstructure indicated that this material was expected to be used as UV-blocking materials.