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Please use this identifier to cite or link to this item: http://apo.ansto.gov.au/dspace/handle/10238/6389

Title: Gradual structural evolution from pyrochlore to defect-fluorite in Y2Sn2-xZrxO7: average vs local structure
Authors: Zhang, Z
Middleburgh, SC
Reyes, M
Lumpkin, GR
Kennedy, BJ
Blanchard, PER
Reynolds, E
Keywords: X-RAY DIFFRACTION
PYROCHLORE
ZIRCONIUM
CATIONS
DEFECTS
FLUORITE
Issue Date: 25-Nov-2013
Publisher: ACS Publications
Citation: Zhang, Z., Middleburgh, S. C., de los Reyes, M., Lumpkin, G. R., Kennedy, B. J., Blanchard, P. E. R., . . . Jang, L.-Y. (2013). Gradual Structural Evolution from Pyrochlore to Defect-Fluorite in Y2Sn2-xZrxO7: Average vs Local Structure. Journal of Physical Chemistry C, 117(50), 26740-26749.
Abstract: 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 defectfluorite at x ∼ 1.0−1.2, X-ray absorption near-edge structure (XANES) results at the Zr L3- and Y L2-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 defectfluorite 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. © 2013, American Chemical Society.
URI: http://dx.doi.org/10.1021/jp408682r
http://apo.ansto.gov.au/dspace/handle/10238/6389
ISSN: 0022-3654
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