Processing and Characterization of Bi_2O_3 and Sm_2O_3 Codoped CeO_2 Electrolyte for Intermediate-Temperature Solid Oxide Fuel Cell

摘要

A series of ceria-based solid solution electrolyte, Bi_2O_3 and Sm_2O_3 codoped CeO_2 (Sm_(0.2-x)Bi_xCe_(0.8)O_(1.9) x = 0, 0.05, 0.10, 0.15, 0.20), were synthesized via a Pechini-type gel route. The phase composition was analyzed by the X-ray diffraction. Present study shows that Sm_(0.2-x)Bi_xCe_(0.8)O_(1.9) is exceedingly stable as a cubic phase in all temperature range. Starting from the Sm_(0.2-x)Bi_xCe_(0.8)O_(1.9) powder with specific surface area of 23.057 m~2/g and using bismuth oxide as sintering aid, the sintering behavior investigation demonstrates that the Sm_(0.2-x)Bi_xCe_(0.8)O_(1.9) green compacts can be densified to nearly theoretical density at 1300℃ for 3 h. The very low sintering temperature prevents excessive grain growth during the heating, which is crucial for obtaining microcrystalline ceramics. In the temperature range of 500°-800℃, AC impedance spectra indicate that the Sm_(0.2-x)Bi_xCe_(0.8)O_(1.9) has much higher ionic conductivity than SDC (Sm_(0.2-x)Ce_(0.8)O_(1.9), and that the highest conductivity value is 3.982 S/m at 750℃. The increased conductivity implies that the effect of cell volume and polarization, associated with Bi~(3+), played an important role in the anion transport of the materials.