Influence of Lithium on the Sintering Behavior and Electrical Properties of Ce0.8Gd0.2O1.9 for Intermediate-Temperature Solid Oxide Fuel Cells

The main purpose of this work is to verify the influence of the addition of lithium on the densification and electrical conductivity of a gadolinium-doped ceria electrolyte. The lithium dopant was added directly during the sol-gel synthesis without a grinding step or the use of a dispersant solution. Electrolytes were prepared from powders and sintered at 1250 and 1500 degrees C. The characterization techniques used were XRD, FTIR spectroscopy, SEM, BET analysis, and electrochemical impedance spectroscopy for ionic conductivity. The densification achieved was >97 and >99% of the theoretical density at sintering temperatures of 1250 and 1500 degrees C, respectively, by adding 2mol% of lithium. The densification of gadolinium-doped ceria is caused by lithium deposition in the grain boundaries, which reduces structural imperfections. The ionic conductivity of lithium-doped pellets sintered at 1250 degrees C is the same as that of pure ones sintered at 1500 degrees C with a maximum value of 5.2x10(-2)Scm(-1) at 800 degrees C. Lithium addition is an effective strategy to reduce the sintering temperature and retain high conductivity values.