Solid oxide fuel cell cathodes by infiltration of La_0.6Sr_0.4Co_0.2Fe_0.8O_{3 - δ} into Gd-Doped Ceria

This paper describes the structure and electrochemical properties of solid oxide fuel cell cathodes prepared by infiltration of La_0.6Sr_0.4Co_0.2Fe_0.8O_{3 - δ} (LSCF) into porous Gd-Doped Ceria (GDC). The GDC scaffolds were prepared by partial sintering of GDC compacts on dense GDC electrolytes. LSCF was introduced into these structures by multiple infiltrations of aqueous nitrate solutions followed by firing. The cathode polarization resistance, measured using electrochemical impedance spectroscopy on symmetrical cells, showed a pronounced minimum as a function of GDC firing temperature at 1100-1200 °C, where the microstructure was well-necked but porous with ~ 300-nm-sized particles. Increasing the infiltrated LSCF loading decreased the polarization resistance up to the highest loading tested, 12.5 vol.%. Decreasing the LSCF firing temperature decreased the polarization resistance due to a decrease in the LSCF feature size from ~ 1 μm at 1200 °C to ~ 50 nm at 800 °C. Thus, the infiltration method allowed separate control over the microstructures of the GDC and LSCF phases. The lowest polarization resistance measured at 600 °C was 0.24 Ω cm².