Synthesis of cerium hydroxycarbonate powders via a hydrothermal technique

Abstract CeOHCO3 powders have been directly synthesized using a hydrothermal process at temperatures as low as 160°C. The well-dispersed powders are obtained in a short period of reaction time during hydrothermal reaction via the hydrolysis of urea. For synthesizing CeOHCO3, the concentration of urea is found to be a crucial determinant, which has significant effects on the morphology of the derived powders. When low urea concentrations are provided, the formed particles are rhomboidal platelets. On the other hand, the high urea concentrations cause the shape of the powders to become prismatic. Increasing the concentration of urea tends to increase the particle size as well as the aspect ratio of CeOHCO3 powders. After further heating at 500°C, a phase transformation from orthorhombic CeOHCO3 to cubic CeO2 takes place. The crystallinity and size of CeO2 strongly depend on the particle size of CeOHCO3.