Effect of polarization on and implications for characterization of LSM-YSZ composite cathodes

Identical strontium-doped LaMnO3 and yttria-doped zirconia (LSM-YSZ) composite electrodes were characterized in three separate cell configurations, in air at 973 K using impedance spectroscopy. These configurations included a single-cell solid oxide fuel cell (SOFC), a symmetric cell (cathode/YSZ/cathode), and a thick pellet half-cell. Large discrepancies were observed in the measurements, with the electrode showing a current-independent area-specific resistance (ASR) of similar to0.2 Omega cm(2) as an SOFC cathode, while nearly identical electrodes in the other two configurations exhibited nonlinear behavior, with ASR as large as 12 Omega cm(2). The discrepancies are partly explained by electrode polarization effects. This has important implications for cathode characterization in SOFC. (C) 2004 The Electrochemical Society.