Average and local ordering of Yb2(Ti2-xYbx)O7-x/2 ‘stuffed’ pyrochlores: the development of a robust structural model
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Date
2021-10-01
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Publisher
Elsevier
Abstract
The long-range (average) and short-range (local) structures in the Yb2(Ti2-xYbx)O7-x/2 (x = 0.00–0.67) series were studied using a combination of diffraction and spectroscopic techniques. The average structure, established from synchrotron X-ray and neutron powder diffraction data, shows the development of multiphase regions from x = 0.134 and the formation of anti-site disorder from x = 0.335. The local structure, established from X-ray absorption near-edge structure (XANES), shows a gradual evolution of short-range disorder. The crystal field splitting energy of the Ti4+ ions decreases from 2.15 to 1.91 eV with increasing Yb3+ content, reflecting the increase in coordination number from 6 to predominantly 7. Electrochemical impedance spectroscopic studies show an increase in oxygen ionic conductivity by almost a factor of 3 upon doping with small amounts of Yb3+ (x = 0.067). These results imply that the disordering across the anion and cation sublattices are different and inducing small amounts of disorder into the pyrochlore structure may lead to applications in solid-oxide fuel cells. © 2021 Elsevier Inc.
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Keywords
Neutron diffraction, X-ray diffraction, Pyrochlore, Crystal structure, Absorption, Oxygen
Citation
Mullens, B. G., Zhang, Z., Avdeev, M., Brand, H. E. A., Cowie, B. C. C., D'Angelo, A., Múzquiz, M. S., & Kennedy, B. J. (2021). Average and local ordering of Yb2(Ti2-xYbx)O7-x/2 ‘stuffed’ pyrochlores: the development of a robust structural model. Journal of Solid State Chemistry, 302, 122412. doi:10.1016/j.jssc.2021.122412