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Regensburg 2013 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 21: Topical Session: TEM-Symposium - HR Imaging & Analytic II

MM 21.2: Talk

Tuesday, March 12, 2013, 12:00–12:15, H4

Electron microscopy study of Y-doped BSCF — •Matthias Meffert1, Philipp Müller1,3, Heike Störmer1, Christian Niedrig2, Stefan F. Wagner2, Ellen Ivers-Tiffée2,3, and Dagmar Gerthsen1,31Laboratorium für Elektronenmikroskopie, KIT, Karlsruhe, Germany — 2Institut für Werkstoffe der Elektrotechnik, KIT, Karlsruhe, Germany — 3DFG Center for Functional Nanostructures, KIT, Karlsruhe, Germany

Mixed ionic-electronic conducting ceramic membranes are well suited for oxygen separation. The cubic phase of perovskite Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) has received particular attention due to its high oxygen permeability. However long-term phase stability at application relevant temperatures (700 - 800 C) is still an issue to be solved. Oxidation of the B-site cation cobalt and a concurrent decrease of ion radius cause a slow decomposition of the cubic BSCF phase. Beside the hexagonal phase precipitates with plate-like morphology are formed which consist of a mixture of different phases.
To improve the stability of the cubic BSCF phase doping with yttrium was investigated using analytical transmission electron microscopy and scanning electron microscopy. Y-doping suppresses the formation of cobalt oxide precipitates which serve as nucleation centers for plate-like precipitates and the hexagonal phase in undoped BSCF. Hence, the hexagonal phase is only formed at grain boundary triple points (800 C) and decorates most grain boundaries at 700 C. Samples annealed at elevated temperatures (≥900 C) are free of secondary phases in contrast to undoped material.

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