The Phosphates ‐ Skipped Reaction Products in the Octahedron‐like Yb and Lu‐Doped Ceria Synthesis.

Abstract

AbstractAn unexpected aggregation effect observed for the octahedron‐like mixed oxides (Ce1‐x(Yb or Lu)xO2‐x/2), but unobserved for the pure ceria crystals, has been described and explained. The aggregation effect is probably due to the presence of Na3PO4*12H2O as a base and Yb3+ in the reaction (octahedrons synthesis) mixture. During the hydrothermal synthesis process, the small octahedron‐like mixed oxide crystals undergo the aggregation process, but in a very specified way. In the pure ceria samples, the octahedral crystals of CeO2 and the rod‐like crystals of cerium phosphate have been observed on the HRTEM images. On the other hand, on the HRTEM images collected for the Ce‐Yb (or Ce‐Lu) mixed oxides, only octahedral aggregates of the octahedron‐like crystals have been found. The EDX measurements show that the amount of phosphorus in case the doped and pure ceria are very similar. The thin layer of P‐phase plays a role of “glue” for the crystals, but at the same time prevent the growth of mixed oxide crystallites. Considering the presence of phosphates in the octahedron like pure and doped ceria particles is crucial to the correct description of the shape dependency of the properties in the ceria based materials.