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Probing oxygen vacancy concentration and homogeneity in solid-oxide fuel-cell cathode materials on the subunit-cell level

Nature Materials volume 11, pages 888–894 (2012)Cite this article

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Abstract

Oxygen vacancy distributions and dynamics directly control the operation of solid-oxide fuel cells and are intrinsically coupled with magnetic, electronic and transport properties of oxides. For understanding the atomistic mechanisms involved during operation of the cell it is highly desirable to know the distribution of vacancies on the unit-cell scale. Here, we develop an approach for direct mapping of oxygen vacancy concentrations based on local lattice parameter measurements by scanning transmission electron microscopy. The concept of chemical expansivity is demonstrated to be applicable on the subunit-cell level: local stoichiometry variations produce local lattice expansion that can be quantified. This approach was successfully applied to lanthanum strontium cobaltite thin films epitaxially grown on substrates of different symmetry, where polarized neutron reflectometry revealed a strong difference in magnetic properties. The different vacancy content found in the two films suggests the change in oxygen chemical potential as a source of distinct magnetic properties, opening pathways for structural tuning of the vacancy concentrations and their gradients.

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Figure 1: Thin-film structures and the STEM–EELS analysis.
Figure 2: Lattice spacing mapping from ADF STEM images.
Figure 3: Representative lattice spacing change and identified brownmillerite LSCO on NGO.
Figure 4: Determination of oxygen content in LSCO.

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Change history

  • 30 August 2012

    In the version of this Article originally published online, in Fig. 2b, the label 'NGO' was incorrectly used instead of 'LSAT'; in Fig. 3d, the labels 'NGO' and 'LSCO' were left out. These errors have been corrected in all versions of the Article.

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Acknowledgements

The work was supported by the Materials Science and Engineering Division of the US DOE. Portions of this research were conducted at the Center for Nanophase Materials Sciences and the Spallation Neutron Source, which are both sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy. The authors are grateful to D. Morgan (U. Wisc) for valuable advice.

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Authors and Affiliations

  1. Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

    Young-Min Kim, Jun He, Sokrates T. Pantelides, Stephen J. Pennycook & Albina Y. Borisevich

  2. Division of Electron Microscopic Research, Korea Basic Science Institute, Daejeon 305-333, South Korea

    Young-Min Kim

  3. Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA

    Jun He, Sokrates T. Pantelides & Stephen J. Pennycook

  4. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

    Michael D. Biegalski, Hans M. Christen & Sergei V. Kalinin

  5. Neutron Science Division, Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

    Hailemariam Ambaye & Valeria Lauter

  6. Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, Tennessee 37235, USA

    Sokrates T. Pantelides

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Contributions

Y-M.K. and A.Y.B. collected and analysed the STEM data, M.D.B. and H.M.C. grew the samples, H.A., V.L. and M.D.B. collected and analysed the PNR data, and J.H. and S.T.P. performed the DFT calculations. All authors contributed to writing the paper. A.Y.B. and S.V.K. conceived and coordinated the project.

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Correspondence to Albina Y. Borisevich.

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Kim, YM., He, J., Biegalski, M. et al. Probing oxygen vacancy concentration and homogeneity in solid-oxide fuel-cell cathode materials on the subunit-cell level. Nature Mater 11, 888–894 (2012). https://doi.org/10.1038/nmat3393

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