Degradation behaviours of Fe-doped La 0.8 Sr 0.2 CoO 3- δ by thermal stress

Abstract

The improvement in durability by Fe doping to La_0.8Sr_0.2CoO_3-δ (LSC) and its degradation mechanism were investigated in terms of structural and morphological analyses. Polarisation resistance of LSC was increased approximately by 65.7% after exposure to thermal stress at 900°C for 100 h because the oxygen reduction reaction was declined by particle coarsening and aggregation of LSC powders. The polarisation resistance of La_0.8Sr_0.2Co_0.8Fe_0.2O_3-δ (LSCF) was increased from 0.269 to 0.328 Ωcm² after the heat treatment. Increasing rate of polarisation resistance of LSCF was 21.9%, which was three times lower than that of LSC due to reduced particle coarsening and aggregation by Fe doping. Particle size of LSCF powders was maintained about 0.5–3 μm, and morphologies were also similar before and after the heat treatment. Chemical reaction between the LSCF and Sm-doped Ceria electrolyte powders did not occur despite the thermal stress, indicating the interface between the cathode and electrolyte is chemically stable.