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dc.contributor.authorBrown, AJ-
dc.contributor.authorSchwaighofer, B-
dc.contributor.authorAvdeev, M-
dc.contributor.authorJohannessen, B-
dc.contributor.authorEvans, IR-
dc.contributor.authorLing, CD-
dc.identifier.citationBrown, A. J., Schwaighofer, B., Avdeev, M., Johannessen, B., Evans, I. R., & Ling, C. D. (2021). Expanded chemistry and proton conductivity in vanadium-substituted variants of γ-Ba4Nb2O9. Chemistry of Materials. doi:10.1021/acs.chemmater.1c02340en_US
dc.description.abstractWe have substantially expanded the chemical phase space of the hitherto unique γ-Ba4Nb2O9 type structure by designing and synthesizing stoichiometric ordered analogues γ-Ba4V1/3Ta5/3O9 and γ-Ba4V1/3Nb5/3O9 and exploring the solid-solution series γ-Ba4VxTa2–xO9 and γ-Ba4VxNb2–xO9. Undoped Ba4Ta2O9 forms a 6H-perovskite type phase, but with sufficient V doping the γ-type phase is thermodynamically preferred and possibly more stable than γ-Ba4Nb2O9, forming at a 200 °C lower synthesis temperature. This is explained by the fact that Nb5+ ions in γ-Ba4Nb2O9 simultaneously occupy 4-, 5-, and 6-coordinate sites in the oxide sublattice, which is less stable than allowing smaller V5+ to occupy the former two and larger Ta5+ to occupy the latter. The x = 1/3 phase γ-Ba4V1/3Ta5/3O9 shows greatly improved ionic conduction compared to the x = 0 phase 6H-Ba4Ta2O9. We characterized the structures of the new phases using a combination of X-ray and neutron powder diffraction. All compositions hydrate rapidly and extensively (up to 1/3 H2O per formula unit) in ambient conditions, like the parent γ-Ba4Nb2O9 phase. At lower temperatures, the ionic conduction is predominately protonic, while at higher temperatures it is likely other charge carriers make increasing contributions.© 2021 American Chemical Societyen_US
dc.publisherAmerican Chemical Societyen_US
dc.subjectX-ray diffrationen_US
dc.subjectTransition elementsen_US
dc.subjectElectric conductivityen_US
dc.subjectThermal gravimetric analysisen_US
dc.subjectNeutron diffractionen_US
dc.titleExpanded chemistry and proton conductivity in vanadium-substituted variants of γ-Ba4Nb2O9en_US
dc.typeJournal Articleen_US
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