Oxygen Exchange in La0.6Sr0.4Co0.2Fe0.8O3-δ Thin-Film Heterostructures under Applied Electric Potential

In situ synchrotron X-ray diffraction was used to investigate oxygen surface exchange behavior in La0.6Sr0.4Co0.2Fe0.8O3-delta/Gd2O3-doped CeO2/Y2O3-stabilized ZrO2 (LSCF/GDC/YSZ) epitaxial thin-film heterostructures. Applying electrical potentials across the heterostructure under high temperature and controlled oxygen partial pressure conditions resulted in significant changes in oxygen vacancy concentrations due to differing rates of oxygen transport across the LSCF/air surface and LSCF/GDC buried interface. These changes in stoichiometry were correlated with time-dependent out-of-plane LSCF lattice parameter changes. An electrochemical reaction rate analysis was used to determine that the rate constant associated with oxygen exchange at the LSCF/air surface dominates the behavior of the sample as a whole and that the rate of oxygen transport across the LSCF/air surface is smaller than or equal to the rate of oxygen transport across the buried LSCF/GDC interface.