1 Department of Energy Conversion and Storage, Technical University of Denmark2 Fundamental Electrochemistry, Department of Energy Conversion and Storage, Technical University of Denmark3 Centro Atómico Bariloche4 Applied Electrochemistry, Department of Energy Conversion and Storage, Technical University of Denmark
Nano-sized La0.4Sr0.6Co0.8Fe0.2O3−δ (LSCF) perovskite samples (prepared by a conventional acetate route and a novel acetate synthesis with HMTA additives), were tested simulating a red–ox cycle. The crystallography was studied by X-ray Powder Diffraction (XPD) and the changes in the oxidation state of the perovskite B-site were evaluated by synchrotron X-ray Absorption Near Edge Spectroscopy (XANES). After a reducing treatment, LSFC particles show the appearance of a new phase that coexists with the original one. The structural change is accompanied by a Co and Fe formal oxidation states decrease, although Fe remains always closer to 4+ and Co closer to 3+. The treatment produces a B-site valence average reduction from 3.52+ to 3.26+ and the formation of oxygen vacancies. A re-oxidation treatment under O2 rich atmosphere at 800°C for 10h shows that the change is reversible and independent of the two chemical methods used to synthesize the LSCF nano-particles.
Journal of Solid State Chemistry, 2013, Vol 198, p. 253-261