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 ℃ 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 ℃ or 900 ℃ could enhance the diffusion of Zr, Y and Bi ions, to form effective diffusion zone for stabilizing δ-Bi₂O₃ matrix. The results showed a dual-structure of 66 mol% 8YSZ-34 m% Bi₂O₃ with up to 76% δ-phase content was stabilized by solid-state sintering, surpassing a bulk conductivity of 10^-2 Scm^-1 at 500 ℃. The coefficient of thermal expansion value exhibited by the composite between 25 ℃ and 650 ℃ 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.

Keywords: Bismuth oxide; zirconia; composite; interface; ionic conductivity