Article abstract

Nature Materials 7, 498 - 504 (2008)
Published online: 18 May 2008 | doi:10.1038/nmat2201

Subject Categories: Ceramics | Materials for energy

Interstitial oxide ion conductivity in the layered tetrahedral network melilite structure

Xiaojun Kuang1, Mark A. Green2,3, Hongjun Niu1, Pawel Zajdel2,4, Calum Dickinson1, John B. Claridge1, Laurent Jantsky1 & Matthew J. Rosseinsky1

High-conductivity oxide ion electrolytes are needed to reduce the operating temperature of solid-oxide fuel cells. Oxide mobility in solids is associated with defects. Although anion vacancies are the charge carriers in most cases, excess (interstitial) oxide anions give high conductivities in isolated polyhedral anion structures such as the apatites. The development of new families of interstitial oxide conductors with less restrictive structural constraints requires an understanding of the mechanisms enabling both incorporation and mobility of the excess oxide. Here, we show how the two-dimensionally connected tetrahedral gallium oxide network in the melilite structure La1.54Sr0.46Ga3O7.27 stabilizes oxygen interstitials by local relaxation around them, affording an oxide ion conductivity of 0.02–0.1 S cm- 1 over the 600–900 °C temperature range. Polyhedral frameworks with central elements exhibiting variable coordination number can have the flexibility needed to accommodate mobile interstitial oxide ions if non-bridging oxides are present to favour cooperative network distortions.

  1. Department of Chemistry, The University of Liverpool, Liverpool, L69 7ZD, UK
  2. NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
  3. Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742-2115, USA
  4. Department of Chemistry, University College London, 20 Gordon Street, London W1X 0AJ, UK

Correspondence to: Matthew J. Rosseinsky1 e-mail:


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