Degradation behaviours of Fe-doped La_0.8Sr_0.2CoO_3-δ by thermal stress

Abstract

The improvement in durability by Fe doping to La 0.8 Sr 0.2 CoO 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 0.8 Sr 0.2 Co 0.8 Fe 0.2 O 3-δ (LSCF) was increased from 0.269 to 0.328 Ωcm 2 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.