Effect of infiltrate solution additives on samarium strontium cobaltite-cerium gadolinium oxide nano-composite SOFC cathodes

Nano-composite SSC (Sm_0.5Sr_0.5CoO_3-x)-GDC (Ce_0.9Gd_0.1O_1.95) Solid Oxide Fuel Cell cathodes were produced by infiltrating SSC nitrate solutions with/without additives into GDC scaffolds. X-ray diffraction indicated that fired precursor solutions containing the surfactant Triton X-100 had less secondary phases than similarly processed pure nitrate solutions. Further, precursor solutions containing citric acid, a chelating agent, produced nearly phase-pure SSC after 1 hour at 800°C These solution additives did not have a large effect on the cathode polarization resistance. In contrast, alterations of the infiltration procedure influenced the SSC nano-particle size and hence the polarization resistance. Polarization resistances of 0.1 Ω·cm² at 600°C were achieved with a single infiltration of concentrated solution. Polarization resistance predictions made using microstructural observations and a modified Tanner, Fung, Virkar model were found to be within 40% (without fitting parameters) of the experimentally measured values, regardless of the testing temperature, cathode thickness, solution additives, and cathode synthesis conditions.