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Correlation of local structure and diffusion pathways in the modulated anisotropic oxide ion conductor CeNbO4.25

DOI: 10.1021/jacs.5b11373 DOI Help
PMID: 26771687 PMID Help

Authors: Stevin S. Pramana (Imperial College London) , Thomas Baikie (Nanyang Technological University) , Tao An (Nanyang Technological University) , Matthew G. Tucker (ISIS Facility; Diamond Light Source) , Ji Wu (Imperial College London) , Martin K. Schreyer (Institute of Chemical and Engineering Sciences, Singapore) , Fengxia Wei (Institute of Materials Research and Engineering, Singapore) , Ryan D. Bayliss (Imperial College London) , Christian L. Kloc (Nanyang Technological University) , Timothy J. White (Nanyang Technological University) , Andrew P. Horsfield (Imperial College London) , Stephen J. Skinner (Imperial College London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of The American Chemical Society , VOL 138 (4) , PAGES pp 1273–1279

State: Published (Approved)
Published: January 2016

Abstract: CeNbO4.25 is reported to exhibit fast oxygen ion diffusion at moderate temperatures, making this the prototype of a new class of ion conductor with applications in a range of energy generation and storage devices. To date, the mechanism by which this ion transport is achieved has remained obscure, in part due to the long-range commensurately modulated structural motif. Here we show that CeNbO4.25 forms with a unit cell ∼12 times larger than the stoichiometric tetragonal parent phase of CeNbO4 as a result of the helical ordering of Ce3+ and Ce4+ ions along z. Interstitial oxygen ion incorporation leads to a cooperative displacement of the surrounding oxygen species, creating interlayer “NbO6” connectivity by extending the oxygen coordination number to 7 and 8. Molecular dynamic simulations suggest that fast ion migration occurs predominantly within the xz plane. It is concluded that the oxide ion diffuses anisotropically, with the major migration mechanism being intralayer; however, when obstructed, oxygen can readily move to an adjacent layer along y via alternate lower energy barrier pathways.

Journal Keywords: Diffusion; Crystal structure; Ions; Oxygen; Physical and chemical processes

Subject Areas: Materials, Chemistry

Instruments: I11-High Resolution Powder Diffraction

Added On: 02/02/2016 15:41

Discipline Tags:

Physical Chemistry Energy Materials Chemistry Materials Science

Technical Tags:

Diffraction X-ray Powder Diffraction