La 0.6Sr 0.4Fe 0.8CO 0.2O 3-δ - Gd doped Ceria (LSCF-GDC) symmetric cathode cells were electrochemically tested at 600°C, after aging at various times and temperatures ranging from 650-850°C. The observed increases in polarization resistance were fit using a combined surface resistance and power-law coarsening kinetics model. Best fits were obtained for a t 0.25 power law applicable to coarsening of isolated particles on a surface, with a surface diffusion activation energy range of 2.52 to 2.86 eV. The model predicts that the resistance would increase from 0.2 to 0.28-0.35 Ωcm 2 (by 39-74%) over 40,000 h at 600°C, due to coarsening. Additionally, evolution of the infiltrated LSCF particles was seen in SEM images of the same location before and after aging treatment. La 1-xSr xMnO 3-δ (LSM) coarsening was also observed for infiltrated LSM- yttria-stabilized-zirconia (YSZ) cathodes, with a corresponding increase in polarization resistance.