The structures, phase transitions and dynamics behind mixed ionic and electronic conduction in hydrated Ba4Nb2O9

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dc.contributor.authorLing, CDen_AU
dc.contributor.authorAvdeev, Men_AU
dc.contributor.authorJohnson, MRen_AU
dc.date.accessioned2021-10-04T23:30:25Zen_AU
dc.date.available2021-10-04T23:30:25Zen_AU
dc.date.issued2010-02-03en_AU
dc.date.statistics2021-09-03en_AU
dc.description.abstractAlthough Ba4Nb2O9 was first synthesised in 1965, [1] its structure remained unsolved until a recent study [2] in which we showed that Ba4Nb2O9 has two basic polymorphs: a high temperature γ phase, which represents an entirely new structure type; and a low-temperature α phase, which has the rare Sr4Ru2O9 structure type. The phases are separated by a reconstructive transition at ~1370 K, the kinetics of which are sufficiently slow that the γ phase can easily be quenched to room temperature. Below ~950 K, both α and γ absorb significant amounts of water. In the γ phase, protons occupy ordered positions, giving rise to a stoichiometric phase γ -III-Ba4Nb2O9.1/3H2O at room temperature. γ-III-Ba4Nb2O9.1/3H2O partially dehydrates at ~760 K to γ-II-Ba4Nb2O9.1/6H2O, then completely dehydrates at ~950 K to γ-I-Ba4Nb2O9. The hydrated γ phases exhibit faster protonic and oxide ionic transport than the hydrated " phases, due to the presence in the gamma phases of 2D layers containing Nb5+ cations with unusually low oxygen coordination numbers (4 or 5) separated by discrete OH groups. In this paper, we will discuss the structures and mechanisms of hydration – and, therefore, of ionic conduction – in the various phases of Ba4Nb2O9 on the basis of neutron diffraction experiments and ab initio (density functional theory) dynamics simulations.en_AU
dc.identifier.citationLing, C. D., Avdeev, M., & Johnson, M. R. (2010). The structures, phase transitions and dynamics behind mixed ionic and electronic conduction in hydrated Ba4Nb2O9. Paper presented to the 34th Annual Condensed Matter and Materials Meeting 2010, Waiheke Island Resort, Waiheke, Auckland, New Zealand 2 - 5 February 2010. Retrieved from: https://physics.org.au/wp-content/uploads/cmm/2010/en_AU
dc.identifier.conferenceenddate5 February 2010en_AU
dc.identifier.conferencename4th Annual Condensed Matter and Materials Meeting 2010en_AU
dc.identifier.conferenceplaceAuckland, New Zealanden_AU
dc.identifier.conferencestartdate2 February 2010en_AU
dc.identifier.isbn978-0-646-53897-6en_AU
dc.identifier.urihttps://physics.org.au/wp-content/uploads/cmm/2010/en_AU
dc.identifier.urihttps://apo.ansto.gov.au/dspace/handle/10238/11873en_AU
dc.language.isoenen_AU
dc.publisherAustralian Institute of Physicsen_AU
dc.subjectPhase transformationsen_AU
dc.subjectHydrationen_AU
dc.subjectIonic conductivityen_AU
dc.subjectPerovskiteen_AU
dc.subjectTantalatesen_AU
dc.subjectOxygenen_AU
dc.subjectNeutron diffractionen_AU
dc.titleThe structures, phase transitions and dynamics behind mixed ionic and electronic conduction in hydrated Ba4Nb2O9en_AU
dc.typeConference Abstracten_AU
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