Hexagonal perovskite related oxide ion conductor Ba3NbMoO8.5: phase transition, temperature evolution of the local structure and properties

Matthew S. Chambers, Kirstie S. McCombie, Josie E. Auckett, Abbie C. McLaughlin, John T.S. Irvine, Philip A. Chater, John S.O. Evans*, Ivana Radosavljevic Evans* (Corresponding Author)

*Corresponding author for this work

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Abstract

Ba3NbMoO8.5 has recently been demonstrated to exhibit competitive oxide ion conductivity and to be stable under reducing conditions, making it an excellent potential electrolyte for solid oxide fuel cells. We report here the first investigation of the local structure in Ba3NbMoO8.5, carried out using variable-temperature neutron total scattering and pair distribution function (PDF) analysis. This work reveals a significant degree of disorder in the material, even at ambient conditions, in both the cation and the anion arrangements and suggests the prevalence of the five-fold Nb/Mo coordination. In addition, high resolution powder X-ray diffraction data indicate that the temperature-dependent structural changes in Ba3NbMoO8.5 are due to a first order phase transition, and reveal a previously unreported effect of thermal history on the room-temperature form of the material. PDF modelling shows that Ba3NbMoO8.5 has an essentially continuous oxygen distribution in the ab plane at 600 °C which leads to its high oxide-ion conductivity.

Original languageEnglish
Pages (from-to)25503-25510
Number of pages8
JournalJournal of Materials Chemistry A
Volume7
Issue number44
Early online date25 Oct 2019
DOIs
Publication statusPublished - 28 Nov 2019

Bibliographical note

M. S. C. thanks Diamond Light Source and Durham University for a PhD studentship. I. R. E. acknowledges the Royal Society and the Leverhulme Trust for the award of a Senior Research Fellowship (SRF\R1\180040). J. E. A. acknowledges the support of a Newton International Fellowship (NF170809) awarded by The Royal Society. We thank Dr Sascha Fop for assistance with TGA-MS experiments and Dr David Apperley for recording the solid state NMR spectra. We gratefully acknowledge the Science and Technology Facilities Council (STFC) for access to neutron beamtime at POLARIS, ISIS (RB1810088), and thank Dr Helen Playford for assistance during the data collection. We acknowledge Diamond Light Source for time on Beamline I11 under Proposal EE19729 and thank Dr Sarah Day and Prof Chiu Tang for assistance during data collection.

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