EXAFS study on the local atomic structures around Ce in CeO2 nanoparticles

CeO2 nanoparticles coated by sodium bis(2-ethylhexyl) sulfosuccinite have b een prepared by using the microemulsion method. An average particle size of 2-3 nm was revealed by using transmission electron microscopy. X-ray diffr action shows that the CeO2 nanoparticles remain the CaF2-type cubic structu res as the bulk crystal. Extended X-ray absorption fine structure technique is used to probe the local atomic structures around the absorber Ce. A dou ble Gaussian model is used to deduce the structural parameters of the first coordination shell. Bulk CeO2 with eight oxygen atoms located at 2.338 Ang strom was used as the reference sample to extract the backscattering amplit ude and phase shift of the Ce-O bond. Our EXAFS data suggest that in CeO2 n anoparticles, the oxygen coordination number around Ce has no obvious decre ase, but the bond-length of Ce-O is obviously elongated. It is postulated t hat a surface/core model may be used to describe the local atomic structure s in the CeO2 nanoparticles. (C) 2000 Elsevier Science S.A. All rights rese rved.