Atomic Resolution Coordination Mapping in Ca2FeCoO5 Brownmillerite by Spatially Resolved Electron Energy-Loss Spectroscopy

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• 作者：Stuart Turner ; Johan Verbeeck ; Farshid Ramezanipour ; John E. Greedan ; Gustaaf Van Tendeloo ; Gianluigi A. Botton
• 刊名：Chemistry of Materials
• 出版年：2012
• 出版时间：May 22, 2012
• 年：2012
• 卷：24
• 期：10
• 页码：1904-1909
• 全文大小：434K
• 年卷期：v.24,no.10(May 22, 2012)
• ISSN：1520-5002

文摘

Using a combination of high-angle annular dark field scanning transmission electron microscopy and atomically resolved electron energy-loss spectroscopy at high energy resolution in an aberration-corrected electron microscope, we demonstrate the capability of coordination mapping in complex oxides. Brownmillerite compound Ca₂FeCoO₅, consisting of repetitive octahedral and tetrahedral coordination layers with Fe and Co in a fixed 3+ valency, is selected to demonstrate the principle of atomic resolution coordination mapping. Analysis of the Co-L_2,3 and the Fe-L_2,3 edges shows small variations in the fine structure that can be specifically attributed to Co/Fe in tetrahedral or in octahedral coordination. Using internal reference spectra, we show that the coordination of the Fe and Co atoms in the compound can be mapped at atomic resolution.

Keywords:

oxygen coordination; valency; electron energy-loss spectroscopy; EELS; energy-loss near edge structure; ELNES; Fe-L_2,3 edge; Co-L_2,3 edge; brownmillerite