Electrochemical properties of La 0.6 Sr 0.4 CoO 3 - δ thin films investigated by complementary impedance spectroscopy and isotope exchange depth profiling.

The oxygen exchange and diffusion properties of La _0.6 Sr _0.4 CoO _3 - δ thin films on yttria stabilized zirconia were analyzed by impedance spectroscopy and ¹⁸ O tracer experiments. The investigations were performed on the same thin film samples and at the same temperature (400 °C) in order to get complementary information by the two methods. Electrochemical impedance spectroscopy can reveal resistive and capacitive contributions of such systems, but an exact interpretation of the spectra of complex oxide electrodes is often difficult from impedance data alone. It is shown that additional isotope exchange depth profiling can significantly help interpreting impedance spectra by giving reliable information on the individual contribution and exact location of resistances (surface, electrode bulk, interface). The measurements also allowed quantitative comparison of electrode polarization resistances obtained by different methods.