Structural defects in a nano-scale powder of CeO2 studied by pulsed neutron diffraction

Pulsed neutron diffraction measurements on nano-scale powder of ceria, CeO2 , uncovered new structural features which appear to be intimately related t o the function of this material as an oxygen storage medium in automotive t hree-way catalytic converters. The results of the pair-distribution functio n (PDF) analysis and the Rietveld refinement of the neutron diffraction dat a indicate the presence of interstitial oxygen defects in the octahedral si tes of the fluorite structure. The defects were found to disappear followin g high-temperature treatment. It is suggested that these weakly bound inter stitial oxygen defects provide oxygen mobility that facilitates the oxygen storage capacity of ceria in the catalytic converters. (C) 2000 Elsevier Sc ience Ltd. All rights reserved.