Atomic-resolution Z-contrast imaging, and electron energy-loss spectroscopy were used to study the defect structures of O-deficient samples after repeated oxidation/reduction cycles at high temperatures. Ordered micro-domains were found in the reduced samples. The Z-contrast imaging revealed ordering on alternating CoO2 planes; characteristic of the brownmillerite-type vacancy-ordered structure. Electron energy-loss spectroscopy showed that the average valence state of Co had decreased after testing. In tested samples, Co was found in the +3 or +2 valence states. Also, CoO2 precipitates were found at grain boundaries and in the triple points of these samples; thus indicating a Co deficiency in the grains.

Characterization of Oxygen-Deficient SrCoO3 by Electron Energy Loss Spectroscopy and Z-Contrast Imaging. S.Stemmer, A.Sane, N.D.Browning, T.J.Mazanec: Solid State Ionics, 2000, 130[1-2], 71-80