Oxygen exchange kinetics on a highly oriented La_0.5Sr_0.5CoO_3-δ thin film prepared by pulsed-laser deposition

Oxygen exchange at a highly oriented La_0.5Sr_0.5CoO_3-δ thin film prepared on (100) surfaces of an yttria-stabilized zirconia single crystal by pulsed-laser deposition was studied with ac impedance spectroscopy under various temperatures and oxygen partial pressures. Three distinctive features observed in the impedance spectra were assigned to contributions from the ionic conduction of the electrolyte, oxide ion transfer across the electrode/electrolyte interface, and the oxygen exchange on the film surface. An equivalent circuit model was proposed to analyze the impedance results, from which the surface chemical exchange coefficients, k_chem, were derived as a function of temperature and oxygen partial pressure.