Fabrication and characterization of solid oxide fuel cell cathodes made from nano-structured LSCF–SDC composite feedstock

Composite La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) and Ce0.8Sm0.2O1.9 (SDC) cathodes for solid oxide fuel cells (SOFCs) were fabricated by axial-injection plasma spraying. Fine mixing of the ceramic phases was achieved by using a nano-structured feedstock that contained both phases agglomerated together in larger particles. Preliminary investigations explored the effects of varying the process parameters, and cathodes were characterized by XRD and SEM. Metal-supported symmetrical cells were made with several promising sets of process parameters, and the polarization resistance was measured from 550 °C to 750 °C. The cathode with the highest electrochemical performance was incorporated into a fuel cell with a yttria-stabilized zirconia (YSZ) electrolyte and a nickel–YSZ anode. A fuel cell with a coarsely-mixed composite cathode was also fabricated, and the effect of the cathode microstructure on cell impedance was studied using the analysis of differential impedance spectra. •A plasma spray process was developed for a nano-structured LSCF-SDC feedstock.•The effect of the cathode microstructure on the cell impedance was investigated.•At higher temperatures, diffusion dominates the impedance of finely-mixed cathodes.•Charge transfer kinetics affects the impedance of coarsely-mixed cathodes.•At lower temperatures, impedances are more strongly affected by the TPB density.