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Durham University

Department of Chemistry

Publication details for Prof. Ivana Evans

Fuller, Chloe A., Berrod, Quentin, Frick, Bernhard, Johnson, Mark R., Clark, Stewart J., Evans, John S. O. & Evans, Ivana Radosavljevic (2019). Brownmillerite-type Sr2ScGaO5 Oxide Ion Conductor: Local Structure, Phase Transition and Dynamics. Chemistry of Materials 31(18): 7395-7404.

Author(s) from Durham

Abstract

Brownmillerite-type Sr2ScGaO5 has been investigated by a range of experimental X-ray and neutron scattering techniques (diffraction, total scattering and spectroscopy) and density functional theory calculations in order to characterise its structure and dynamics. The material undergoes a second-order phase transition on heating during which a rearrangement of the (GaO4/2)∞ tetrahedral chains occurs, such that they change from being essentially fully-ordered in a polar structure at room temperature to being orientationally disordered above 400 oC. Pair distribution function analysis carried out using neutron total scattering data suggests that GaO4 tetrahedra remain as fairly rigid units above and below this transition, whereas coordination polyhedra in the (ScO6/2)∞ layers distort more. Inelastic neutron scattering and phonon calculations reveal the particular modes that facilitate this structural change which may assist ionic conductivity in the material at higher temperatures. Based on the correlations between these findings and the measured conductivity, we have synthesised a derivative compound with increased conductivity and suggest a possible conduction mechanism in these brownmillerite-type solid electrolytes.