The oxygen exchange kinetics of thin films of the oxygen-deficient double perovskite PrBaCo2O5+δ (PBCO) have been determined by electrical conductivity relaxation (ECR) and by oxygen-isotope exchange and depth profiling (IEDP). Microstructural studies indicate that the PBCO films, prepared by pulsed laser deposition, have excellent single-crystal quality and epitaxial nature. The ECR and IEDP measurements reveal that the PBCO films have high electronic conductivity and rapid surface exchange kinetics, although the ECR data indicate the presence of two distinct kinetic pathways. The rapid surface kinetics compared with those of other perovskites suggest the application of PBCO as a cathode material in intermediate-temperature solid oxide fuel cells.

Solid-state electrochemical cells with dense oriented thin film electrodes of La 0.5 Sr 0.5 CoO 3Ϫ␦ (LSCO) were prepared on (100) surfaces of single-crystal disks of yttria-stabilized zirconia (YSZ) by the pulsed laser deposition technique. Oxygen exchange at the electrodes was studied with alternating current impedance spectroscopy under various temperature and oxygen partial pressure conditions. Three distinctive features were observed in the impedance spectra from high to low frequency corresponding to contributions from the ionic conduction of the YSZ electrolyte, ionic transfer at the LSCO/YSZ interface, and the oxygen exchange on the LSCO electrode surface. An equivalent circuit model of the electrode process is used to fit the impedance data. The time constant for the oxygen surface exchange was derived from the impedance simulation. The surface chemical exchange coefficients, k chem , were calculated from the time constants as a function of temperature and pO 2 . k chem is 7 ϫ 10 Ϫ4 cm/s at T ϭ 700ЊC and pO 2 ϭ 1 atm. The activation energy at pO 2 ϭ 1 atm is Ϸ1.1 eV. The interfacial conductivity data were also derived from the impedance simulations as a function of temperature and pO 2 . The activation energy for the interfacial transport at pO 2 ϭ 1 atm is Ϸ1.6 eV.

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Oxygen exchange at a highly oriented La0.5Sr0.5CoO3−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, kchem, were derived as a function of temperature and oxygen partial pressure.

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