Regensburg 2022 – wissenschaftliches Programm
KFM 13.3: Vortrag
Dienstag, 6. September 2022, 10:45–11:00, H46
Defects and Phase Formation in Non-Stoichiometric LaFeO3: A Combined Theoretical and Experimental Study — •Daniel Mutter1, Roland Schierholz2, Daniel Urban1, Sabrina Heuer2,3, Thorsten Ohlerth2,3, Hans Kungl2, Christian Elsässer1,4, and Rüdiger-A. Eichel2,3 — 1Fraunhofer IWM, Freiburg — 2Forschungszentrum Jülich, IEK-9 — 3RWTH Aachen, Institute of Physical Chemistry — 4FMF, Universität Freiburg
Defect engineering of perovskite compounds has become increasingly popular as it offers the possibility to influence their catalytic properties for applications in energy storage and conversion devices such as solid-oxide fuel- and electrolyser cells. We present results of a combined theoretical and experimental study exploring the feasibility for an active manipulation of the La stoichiometry, and thereby the valence state of Fe, in LaFeO3, which can be regarded as a base compound of the family of catalytically active La1−xAxFe1−yByO3−δ compounds. Concentrations of point defects are presened, derived from formation energies which were calculated by first-principles DFT+U calculations as a function of experimental processing conditions, resulting in predictions of achievable stoichiometry ranges. In the experimental part, LFO was synthesized with a targeted La-site deficiency, and we analyzed the phases in detail by X-ray diffraction and various electron microscopy methods (STEM, EDS, EELS). Instead of a variation of the La/Fe ratio, a mixture of two phases, Fe2O3/LaFeO3, was observed, resulting in an invariant charge state of Fe, which is in line with the theoretical results.