Cerium-Reduction-Induced Defects Clustering, Ordering, and Associated Microstructure Evolution in Yttrium-Doped Ceria

The microstructure, local chemistry, and related evolution of yttrium-doped ceria (YDC) in a reducing environment have been comprehensively characterized by means of electron microscopy and electron energy loss spectroscopy. Long-range ordered features (i.e., superstructures) appear in 25 atom % YDC sintered at high temperature. By combining experimental and atomistic simulation techniques, the ordered structures of defect clusters containing reduced Ce3+ and associated charge-compensating oxygen vacancies have been elucidated. Related microstructure evolution has thereby been explained in terms of the development of ordered defect clusters. In addition, the corresponding diffraction patterns of long-range ordered defect structures embedded in a fluorite lattice have been simulated according to this model, which perfectly matches with experimental diffraction patterns. Such microstructural evolution accompanied by highly ordered defect structures is believed to have strong influence on the ionic conductivity and overall performance of solid oxide fuel cells.