Investigation of the relationship between the structure and conductivity of the novel oxide ionic conductor Ba3MoNbO8.5
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A variable temperature neutron diffraction study of the novel oxide ion conductor Ba3MoNbO8.5 has been performed between 25 and 600 °C. Nonmonotonic behavior of the cell parameters, bond lengths, and angles are observed indicating a structural rearrangement above 300 °C. The oxygen/vacancy distribution changes as the temperature increases so that the ratio of (Mo/Nb)O4 tetrahedra to (Mo/Nb)O6 octahedra increases upon heating above 300 °C. A strong correlation between the oxide ionic conductivity and the number of (Mo/Nb)O4 tetrahedra within the average structure of Ba3MoNbO8.5 is observed. The increase in the number of (Mo/Nb)O4 tetrahedra upon heating from 300-600 °C most likely offers more low energy transition paths for transport of the O2- ions enhancing the conductivity. The unusual structural rearrangement also results in relaxation of Mo(1)/Nb(1) and Ba(2) away from the mobile oxygen, increasing the ionic conductivity. The second order Jahn-Teller effect most likely further enhances the distortion of the MO4/MO6 polyhedra as distortions created by both electronic and structural effects are mutually supportive.
Fop , S , Wildman , E J , Irvine , J T S , Connor , P A , Skakle , J M S , Ritter , C & McLaughlin , A C 2017 , ' Investigation of the relationship between the structure and conductivity of the novel oxide ionic conductor Ba 3 MoNbO 8.5 ' , Chemistry of Materials , vol. 29 , no. 9 , pp. 4146-4152 . https://doi.org/10.1021/acs.chemmater.7b01298
Chemistry of Materials
Copyright © 2017, American Chemical Society. This work is made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1021/acs.chemmater.7b01298
DescriptionThis research was supported by the Northern Research Partnership and the University of Aberdeen. We also acknowledge STFC-GB for provision of beamtime at the ILL.
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