Effect of La0.6Sr0.4Co0.2Fe0.8O3-δ microstructure on oxygen surface exchange kinetics

La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) is a mixed ionic-electronic conducting perovskite (ABO3) material which has attracted significant research interest in recent years as a cathode for solid oxide fuel cell (SOFC) applications at intermediate temperatures (500 °C-750 °C). Fundamental understanding of the oxygen surface exchange kinetics and diffusion in LSCF cathodes is necessary to optimize the cell performance at the required operating temperatures. In this study, we controlled the surface microstructure and crystalline orientation of LSCF thin films on (100) Gd2O3-doped CeO2 thin films (GDC) prepared by pulsed laser deposition on yttria-stabilized zirconia (YSZ) single crystal substrates. Tailoring of the LSCF microstructure was achieved by modifying the underlying GDC thin film surface morphology and microstructure. To clarify the effect of the LSCF microstructure on its oxygen surface exchange kinetics, we employed the 18O/16O oxygen isotope exchange technique in conjunction with secondary ion mass spectroscopy (SIMS) depth profile analysis. Comparison of the qualitative features of the measured concentration of the 18O profile and evaluation of the oxygen surface exchange coefficient k* were performed and the results correlated to the LSCF microstructure.