title: Cubic Sr2ScGaO5Perovskite: Structural Stability, Oxygen Defect Structure, and Ion Conductivity Explored on Single Crystals.
abstract: Oxygen-deficient Sr2ScGaO5single crystals with a cubic perovskite structure were grown by the floating-zone technique. The transparent crystals of this pure 3D oxygen electrolyte are metastable at ambient temperature, showing one-sixth of all oxygen positions vacant. While neutron single-crystal diffraction, followed by maximum entropy analysis, revealed a strong anharmonic displacements for the oxygen atoms, a predominant formation of ScO6octahedra and GaO4tetrahedra is indicated by Raman spectroscopic studies, resulting in a complex oxygen defect structure with short-range order. Temperature-dependent X-ray powder diffraction (XPD) and neutron powder diffraction (NPD) studies reveal the cubic Sr2ScGaO5to be thermodynamically stable only above 1400 °C, while the stable modification below this temperature shows the brownmillerite framework with orthorhombic symmetry. Cubic Sr2ScGaO5remains surprisingly kinetically stable upon heating from ambient temperature to 1300 °C, indicating a huge inertia for the retransformation toward the thermodynamically stable brownmillerite phase. Ionic conductivity investigated by impedance spectroscopy was found to be 10-4S/cm at 600 °C, while oxygen18O/16O isotope exchange indicates a free oxygen mobility to set in at around 500 °C.
authors.affiliation: Institut Charles Gerhardt, UMR 5253 CNRS-UM-ENSCM, Université Montpellier , Montpellier Cedex 5, France.
authors.forename: Serena
authors.initials: S
authors.lastname: Corallini
authors.affiliation: Institut Charles Gerhardt, UMR 5253 CNRS-UM-ENSCM, Université Montpellier , Montpellier Cedex 5, France.
authors.forename: Monica
authors.identifier: http://orcid.org/0000-0001-9704-8251
authors.initials: M
authors.lastname: Ceretti
authors.affiliation: Laboratoire Léon Brillouin, UMR12, CEA-CNRS, CEA Saclay , 91191 Gif Sur Yvette, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Cousson
authors.affiliation: Institut Laue-Langevin , BP 156, 38042 Grenoble, France.
authors.forename: Clemens
authors.initials: C
authors.lastname: Ritter
authors.affiliation: Institut Charles Gerhardt, UMR 5253 CNRS-UM-ENSCM, Université Montpellier , Montpellier Cedex 5, France.
authors.forename: Marco
authors.initials: M
authors.lastname: Longhin
authors.affiliation: Institut Charles Gerhardt, UMR 5253 CNRS-UM-ENSCM, Université Montpellier , Montpellier Cedex 5, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Papet
authors.affiliation: Institut Charles Gerhardt, UMR 5253 CNRS-UM-ENSCM, Université Montpellier , Montpellier Cedex 5, France.
authors.forename: Werner
authors.initials: W
authors.lastname: Paulus