Effects of co-doped barium cerate additive on morphology, conductivity and electrochemical properties of samarium doped ceria electrolyte for intermediate temperature solid oxide fuel cells

The composite of samarium doped ceria (Sm0.2Ce0.8O2-delta, SDC) and co-doped barium cerate (BaZr0.1Ce0.7Y0.1Yb0.1O3-delta, BZCYYb) is prepared by mechanical mixing and investigated as electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs). Coexistence of SDC and BZCYYb are observed for composite electrolyte by X-ray diffraction after sintering at 1500 degrees C for 5 h, while the slight deviation of the diffraction peak indicating the element diffusion between two phases. The scanning electron microscope and electron probe microanalyzer results demonstrate that small BZCYYb grains disperse uniformly around the grains of SDC, limiting the growth of SDC grains and decreasing the average grain size of composite electrolyte. Impedance spectroscopy measurement reveals that the grain boundary resistance can be significantly reduced by about an order of magnitude through adding 15-30 wt. % BZCYYb to SDC. Single cells based on the composite electrolyte are fabricated using nickel cermet (Ni-SDC) anode and perovskite (La0.6Sr0.4Co0.2Fe0.8O3-delta, LSCF) cathode.