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Title: Crystal structure of brownmillerite Ba{sub 2}InGaO{sub 5}

Ba{sub 2}InGaO{sub 5} was prepared by high-temperature solid-state reaction. This compound adopts a brownmillerite structure below 1200 °C, which was not found in past studies of Ba{sub 2}(In{sub 1−x}Ga{sub x}){sub 2}O{sub 5}. Combined structure refinements against neutron and X-ray powder diffraction data show that this material adopts a layered ordering of In and Ga. This is one of a few examples of such an ordering in the brownmillerite structure solely due to size difference between the B cations. This ordering further stabilizes the brownmillerite crystal structure compared to other compositions at smaller Ga contents (x<0.5), for which the transition to a disordered cubic perovskite occurs at a much lower temperature. As could be expected, such stronger ordering is detrimental to ionic conductivity. - Graphical abstract: In/Ga cation ordering occurs only for the x=1/2 composition in brownmillerite Ba{sub 2}(In{sub 1−x}Ga{sub x}){sub 2}O{sub 5}. The increased ordering results in an anomalously higher disordering transition temperature to the cubic perovskite. - Highlights: • Ba{sub 2}InGaO{sub 5} has been synthesized with a brownmillerite structure. • Structure refinements show a layered ordering of In and Ga along the stacking axis. • Ionic conductivity is impeded by the stronger structural ordering. • The temperature required tomore » disorder into a cubic perovskite is higher when such ordering occurs.« less
Authors:
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Publication Date:
OSTI Identifier:
22443408
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 218; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CATIONS; CRYSTAL STRUCTURE; IONIC CONDUCTIVITY; NEUTRONS; PEROVSKITE; SOLIDS; TRANSITION TEMPERATURE; X-RAY DIFFRACTION