The Crystal Structure of Ba3Nb2O8 Revisited: A Neutron Diffraction and Solid-State NMR Study

Eve J. Wildman, Abbie C. McLaughlin, James F MacDonald, John V Hanna, Janet M S Skakle

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Abstract

The structure of Ba3Nb2O8 has been investigated using high resolution neutron powder diffraction. Our results show that whilst the structure has some features in common with the 9R perovskite and palmierite structures, it is a new and distinct structure. It is shown to follow a (chh)(hhc)(chh) sequence with BaO3-packing layers and is a cation and aniondeficient 9H perovskite polytype. Nb atoms occupy octahedral sites with vacancies between hexagonal close-packed layers. Isolated, corner-sharing and face-sharing Nb-O octahedra all occur within the unit cell. The identification of purely octahedral Nb is supported by solid state 93Nb wideline NMR measurements. A two-component line shape was detected: a narrow featureless resonance with an isotropic chemical shift of δiso –928 ± 5 ppm consistent with regular Nb octahedra,
and a much broader featureless resonance with an approximate isotropic chemical shift in the range δiso ~–944 - –937 ± 10 ppm consistent with Nb octahedra influenced by O vacancies. These are both characteristic of six-fold oxo-coordinated Nb environments. The highly distorted octahedral environments in Ba3Nb2O8 make it a potential candidate for dielectric and photocatalytic applications.
Original languageEnglish
Pages (from-to)2653-2661
Number of pages9
JournalInorganic Chemistry
Volume56
Issue number5
Early online date10 Feb 2017
DOIs
Publication statusPublished - 2017

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