NMR of Vacancies: Defect Structures and Mobility in Doped Perovskites and Related Phases

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• Frédéric Blanc (Department of Chemistry)
• Monday 25 October 2010, 16:00-17:00
• Harker 2 lecture room, Department of Earth Sciences, Downing Site.

If you have a question about this talk, please contact Ian Farnan.

Solid state NMR spectroscopy has been used to investigate the local structure and mobility of a series of doped perovskite ABO3 for use as electrolyte materials in solid oxide fuel cells.1 Both materials that function via oxygen anion O2- or proton H+ transport will be investigated. To induce anionic and protonic motions, crystallographic defects in these materials are needed and are obtained by substitution of metal cations Mn+ by lower valence cations M(n-1)+ in the same crystallographic site. 2,3 Observation of any local defects and clustering nearby the defects using diffraction based-techniques is thus not straightforward. While the defects cannot be observed directly by NMR , we will show that we can perform both experimental and computational multinuclear solid state NMR spectroscopy analysis to determine the coordination environment of the metals and thus locate the oxygen defects.4-6 Preliminary results on the direct observation of anionic O2- and protonic H+ motions will also be demonstrated. The application of the approach to investigate Sr- and Mg-doped LaMO3 (M = Ga, Al), and Y/Sc doped BaMO3 (M = Zr, Sn) perovskites will be presented.

References: (1) Ishihara, T. Perovskite Oxide for Solid Oxide Fuel Cells; Springer: Boston, 2002. (2) Boivin, J. C.; Mairesse, G. Chem. Mater. 1998, 10, 2870. (3) Kreuer, K. D. Ann. Rev. Mat. Res. 2003, 33, 333. (4) Middlemiss, D. S.; Blanc, F.; Grey, C. P. E. C. S. Transactions 2009, 25, 1709. (5) Middlemiss, D. S.; Blanc, F.; Pickard, C. J.; Grey, C. P. J Magn Reson 2010, 204, 1. (6) Buannic, L.; Blanc, F.; Hung, I.; Gan, Z.; Grey, C. P. J. Mat. Chem. 2010, 20, 6322.

This talk is part of the Mineral Sciences Seminars series.

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• Department of Earth Sciences seminars
• Harker 2 lecture room, Department of Earth Sciences, Downing Site
• Mineral Sciences Seminars

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