Investigation of the relationship between the structure and conductivity of the novel oxide ionic conductor Ba3MoNbO8.5
Abstract
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.
Citation
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
Publication
Chemistry of Materials
Status
Peer reviewed
ISSN
0897-4756Type
Journal article
Description
This 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.Collections
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