Regensburg 2022 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 14: Materials for Storage and Conversion of Energy (joint session MM/KFM)

MM 14.3: 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 Heuer^2,3, Thorsten Ohlerth^2,3, Hans Kungl², Christian Elsässer^1,4, and Rüdiger-A. Eichel^2,3 — 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 La_1−xA_xFe_1−yB_yO_3−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.