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DOI

  • Zhaoming Zhang
  • Simon C. Middleburgh
    Australian Nuclear Science and Technology Organisation
  • Massey de los Reyes
  • Gregory R. Lumpkin
  • Brendan J. Kennedy
  • Peter E. R. Blanchard
  • Emily Reynolds
  • Ling-Yun Jang
We have studied the long-range average and local structures in Y2Sn2-xZrxO7 (x = 0-2.0) using synchrotron X-ray powder diffraction and X-ray absorption spectroscopy, respectively, and by theoretical methods. While the diffraction data indicate a clear phase transition from ordered pyrochlore to disordered defect-fluorite at x similar to 1.0-1.2, X-ray absorption near-edge structure (XANES) results at the Zr L-3- and Y L-2-edges reveal a gradual structural evolution across the whole compositional range. These findings provide experimental evidence that the local disorder occurs long before the pyrochlore to defect-fluorite phase boundary, as determined by X-ray diffraction, and the extent of disorder continues to develop throughout the defect-fluorite region. The Zr and Y L-edge spectra are very sensitive to changes in the local structure; such sensitivity enables us to reveal the progressive nature of the phase transition. Experimental results are supported by ab initio atomic scale simulations, which provide a mechanism for disorder to initiate in the pyrochlore structure. Further, the coordination numbers of the cations in both the defect-fluorite and pyrochlore structures are predicted, and the trends agree well with the experimental XANES results. The calculations predict that the coordination of cations in the Y2Zr2O7 defect-fluorite (normally considered to be 7 for all cations) varies depending on the species with the average coordination of Y and Zr being 7.2 and 6.8, respectively.
Original languageUnknown
Pages (from-to)26740-26749
Number of pages10
JournalJournal of Physical Chemistry C
Volume117
Issue number50
DOIs
Publication statusPublished - 19 Dec 2013
Externally publishedYes
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