Processing of high conductive Bi2O3/8YSZ composites as SOFC electrolyte

Dual-phasic composites consisted of continuous Bi2O3 matrix and 8 mol% yttria stabilized zirconia particulates were prepared by solid-state-sintering or liquid-phase-sintering, and investigated over the temperature range between 250-650 degrees C to reveal good electrical conductivity and matched thermal expansion to the components used for intermediate-temperature solid oxide fuel cell (SOFC). Interface reactions occurred during sintering either at 750 degrees C or 900 degrees C could enhance the diffusion of Zr, Y and Bi ions, to form effective diffusion zone for stabilizing delta-Bi2O3 matrix. The results showed a dual-structure of 66 mol% 8YSZ-34 m% Bi2O3 with up to 76% delta-phase content was stabilized by solid-state sintering, surpassing a bulk conductivity of 10(-2) Scm(-1) at 500 degrees C. The coefficient of thermal expansion value exhibited by the composite between 25 degrees C and 650 degrees C was found to be 10-12.2 ppm*K-1, which was in good agreement with that of CeO2-based electrolyte. Thus, it was confirmed that the addition of ZrO2 could stabilize the Bi2O3, by improving its capability as a solid electrolyte for intermediate temperature SOFC.