The performance of nanoscaled Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) thin-film cathodes was investigated by electrochemical impedance spectroscopy (EIS). Thin-film cathodes derived by metal-organic deposition on Ce0.9Gd0.1O1.95 electrolyte pellets exhibited a film thickness of <100 nm. Performance evaluations of the nanoscaled BSCF thin-film cathodes were systematically conducted on symmetrical cells by EIS with varying temperatures and oxygen partial pressures in the range of 500-625 degrees C and 0.01-0.5 atm, respectively. The impedance data were then analyzed by calculating the distribution of relaxation times (DRT) and by complex nonlinear least squares fitting. Five independent processes associated with the cathode reaction were identified. Area-specific polarization resistances as low as 39 m Omega cm(2) were measured at 600 degrees C. (C) 2014 The Electrochemical Society. All rights reserved.