Microstructural Control of LSM/YSZ Composite Cathode for Lower Temperature Operation of SOFC

La_0.8Sr_0.3MnO₃(LSM)/Y₂O₃ stabilized ZrO₂(YSZ) composite powders were mechanically prepared. By changing the mechanical device or processing time, three composite powders with different size distributions were obtained. Then the powders were formed into cathodes of solid oxide fuel cells (SOFCs). The microstructures of the cathodes were carefully characterized by scanning electron microscope (SEM). Losses by internal resistance (IR) and by polarization between the electrolyte and cathode were measured with the current interruption technique. The cathode fabricated by using the powder with the narrowest particle size distribution showed fine grains, uniform porous structure and good contact with the electrolyte layer, thereby resulting in low IR and polarization losses. In contrast, the cathode fabricated from the powder with the broadest particle size distribution contained a large mass of coarse particles and had less uniform structure in the grains and pores, thereby resulting in relatively high IR and polarization losses.