Neutron diffuse scattering in Y2O3- and Sc2O3-doped CeO2

Abstract

CeO2 is a fluorite structured oxide which exhibits fast oxygen-ion transport when doped with trivalent impurities. At low concentration the predominate defect formed is a single oxygen vacancy partially compensated by one M3+ ion. However, as concentration is increased, more complex clusters develop. To elucidate the differences in defect structure, we have measured the diffuse neutron scattering for CeO2: 6 m/o Y2O3, CeO2: 15 m/o Y2O3 and CeO2: 1 m/o Sc2O3 + 1 m/o Y2O3. It was found that the scattering in the Q range measured (0.5A−1 to 4.5A−1) is relatively insensitive to the number of associated point defects, but is dominated by the local lattice displacements. Best agreement is obtained with cluster models in which cations coordinating the vacancy move away from the vacancy along <111> by ∼0.2 Å and anions coordinating the vacancy move toward the vacancy along <100> by ∼0.3Å.