Chemical characterization of surface precipitates in La0.7Sr0.3Co0.2Fe0.8O3-δ as cathode material for solid oxide fuel cells

In this study, a strontium doped lanthanum cobalt ferrite thin film with 30% Sr on A-site, denoted as La0.7Sr0.3Co0.2Fe0.8O3-delta or LSCF-7328, is investigated before and after annealing at 800 degrees C under CO2 containing atmosphere for 9 h. The formation of secondary phases on surface of post-annealed LSCF-7328 is observed using atomic force microscope (AFM) and scanning electron microscope (SEM). The extent of Sr segregation at the film surface is monitored using the synchrotron-based total reflection Xray fluorescence (TXRF) technique. The bonding environment of the secondary phases formed on the surface is investigated by synchrotron-based hard X-ray photoelectron spectroscopy (HAXPES). Scanning transmission electron microscopy (STEM) and related spectroscopy techniques are used for micro structural and quantitative elemental analyses of the secondary phases on surface. These studies reveal that the secondary phases on surface consist of SrO covered with a capping layer of SrCO3. The formation of Co-rich phases is observed on the surface of post-annealed LSCF-7328. (C) 2016 Elsevier B.V. All rights reserved.