Electrochemical Analysis of Nanoscaled Ba0.5Sr0.5Co0.8Fe0.2O3-δ Thin-Film Cathodes

Nanoscaled Ba0.5Sr0.5Co0.8Fe0.2O3-δ thin-film cathodes deposited by spin-coating followed by pyrolysis of the metal organic precursors (the metal organic deposition [MOD] process) with a film thickness below 100 nm on Ce0.9Gd0.1O1.95 electrolyte pellets were investigated with a focus on the cathode reaction processes. Electrochemical impedance spectroscopy was carried out under systematic variation of the temperature (T = 500-625 °C) and oxygen partial pressure (pO2 = 0.01-0.5 atm). The impedance data were then analyzed by calculating the distribution of relaxation times (DRT) and performing complex nonlinear least squares (CNLS) fitting. Five processes were identified in the cathode reaction. Area specific polarization resistances as low as ASRpol = 39 mΩ cm2 at 600 °C were found.