Crystal growth of Ce2O(CO3)2·H2O in aqueous solutions: Film formation and samarium doping

Crystalline cerium oxide carbonate hydrate (Ce2O(CO3)2·H2O) was grown in aqueous solutions at a low temperature of 80 °C under ambient pressure. When cerium nitrate was used as a starting material, large Ce2O(CO3)2·H2O particles were precipitated through homogeneous nucleation and subsequent fast crystal growth. In contrast, the usage of cerium chloride was found to promote the preferential precipitation of Ce2O(CO3)2·H2O on foreign substrates through heterogeneous nucleation and slow crystal growth. This phenomenon was applied to a chemical bath deposition of Ce2O(CO3)2·H2O films. Immersion of glass substrates in the solution at 80 °C for typically 24 h resulted in formation of solid films with a unique morphology like a micrometer-scale brush. It was also found that samarium could be incorporated into Ce2O(CO3)2·H2O during the crystal growth in the solutions, as evidenced by characteristic photoluminescence of Sm3+ in heating products of CeO2. These results suggest that rare-earth oxide carbonate hydrates with a variety of compositions and morphologies can be synthesized from the aqueous solutions.