Size-induced lattice relaxation in CeO2 nanoparticles

Size-induced lattice relaxation was observed for nanoscale CeO2 single crystals with an average size from 4 to 60 nm. Results showed the finest crystallites exhibited no strain-induced line broadening, while high temperature annealing resulted in larger grain sizes and significant strains. The observed shift in the x-ray diffraction lattice parameters was assumed to be due to the formation of defects on the lattice, specifically oxygen vacancies. Modeling revealed that the oxygen vacancy concentration ([VO••]) was found to be ≈4×1020/cm3 for the 4 nm crystallites, and decreased two orders of magnitude for larger 60 nm single crystals.