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Structure and dehydration mechanism of the proton conducting oxide Ba2In2O5(H2O)(x)
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics. Chalmers, Dept Appl Phys, SE-41296 Gothenburg, Sweden..
Rutherford Appleton Lab, STFC, ISIS Facil, Didcot OX11 0QX, Oxon, England..
Chalmers, Dept Appl Phys, SE-41296 Gothenburg, Sweden..
Chalmers, Dept Appl Phys, SE-41296 Gothenburg, Sweden..
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2016 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 4, no 4, 1224-1232 p.Article in journal (Refereed) PublishedText
Abstract [en]

The structure and dehydration mechanism of the proton conducting oxide Ba2In2O5(H2O)(x) are investigated by means of variable temperature (20-600 degrees C) Raman spectroscopy together with thermal gravimetric analysis and inelastic neutron scattering. At room temperature, Ba2In2O5(H2O)(x) is found to be fully hydrated (x = 1) and to have a perovskite-like structure, which dehydrates gradually with increasing temperature and at around 600 degrees C the material is essentially dehydrated (x approximate to 0.2). The dehydrated material exhibits a brownmillerite structure, which is featured by alternating layers of InO6 octahedra and InO4 tetrahedra. The transition from a perovskite-like to a brownmillerite-like structure upon increasing temperature occurs through the formation of an intermediate phase at ca. 370 degrees C, corresponding to a hydration degree of approximately 50%. The structure of the intermediate phase is similar to the structure of the dehydrated material, but with the difference that it exhibits a non-centrosymmetric distortion of the InO6 octahedra that is not present in the dehydrated material. The dehydration process upon heating is a two-stage mechanism; for temperatures below the hydrated-to-intermediate phase transition, dehydration is characterized by a homogenous release of protons over the entire oxide lattice, whereas above the transition a preferential desorption of protons originating in the nominally tetrahedral layers is observed. Furthermore, our spectroscopic results point towards the co-existence of two structural phases, which relate to the two lowest-energy proton configurations in the material. The relative contributions of the two proton configurations depend on how the sample is hydrated.

Place, publisher, year, edition, pages
2016. Vol. 4, no 4, 1224-1232 p.
National Category
Materials Chemistry
URN: urn:nbn:se:uu:diva-280104DOI: 10.1039/c5ta05728kISI: 000368837800011OAI: oai:DiVA.org:uu-280104DiVA: diva2:910112
Swedish Research Council, 2010-3519Swedish Research Council, 2011-4887
Available from: 2016-03-08 Created: 2016-03-08 Last updated: 2016-03-08Bibliographically approved

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