Structural Characteristics of Cerium Oxide Nanocrystals Prepared by the Microemulsion Method

The aim of this work is to investigate the microstructure development of cerium oxide nanocrystal, prepared by the microemulsion process, as a function of annealing temperature in air. Combined with the HRTEM and the thermogravimetric−differential thermal analysis (TG−DTA), the XRD patterns reveal that the sample annealed at 623 K is amorphous, and the formation of cerium oxide nanocrystal occurs above 773 K. The local structural and electronic properties in the nanocrystallization process are probed by X-ray absorption spectra (XAS) at the Ce L 3 edge. It is found that the phase structure changes from triclinic to cubic (CeO 2 ), and the electronic structure changes from Ce 3+ to Ce 4+ upon increasing the annealing temperature.