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Ionomigration of Neutral Phases in Ionic Conductors

Authors

  • I.-Wei Chen,

    Corresponding author
    1. Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104-6272, USA
    • Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104-6272, USA.
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  • Seung-Wan Kim,

    1. Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104-6272, USA
    2. Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
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  • Ju Li,

    1. Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104-6272, USA
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  • Suk-Joong L. Kang,

    1. Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
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  • Fuqiang Huang

    1. State Key Laboratory of High Performance, Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China
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Abstract

Without sensing any physical force, a neutral object in an ion conducting solid can move in a uniform electrochemical field by coupling a global ion wind with localized counterion diffusion at the interface. This happens to pores and gas bubbles at 840 °C in a fast O2− conductor, yttria-stabilized zirconia (YSZ), despite having cations that are essentially frozen with lattice diffusivities 1012 times slower than the O2− diffusivity. Through-thickness migration and massive electro-sintering in thin YSZ ceramics are observed at voltages similar to those in YSZ fuel cells and electrolysis cells. This effect should apply to any electrochemically-loaded multiphase ionic conducting solid, with or without an electric field, and can lead to electrolyte sintering, phase accumulation and electrode debonding, resulting in unexpected benefit or damage in electrochemical devices. As the velocity obeys a pseudo Stokes-Einstein equation, inversely proportional to the object size, an especially enhanced size effect is expected in nanocomposites.

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