OXIDE-ION CONDUCTING SOLID ELECTROLYTES BASED ON BI2O3

The high oxide ion conductivity of solid solutions of bismuth oxide wa s initially discovered by Takahashi and coworkers. The bismuth oxide b ased compounds are much better solid electrolytes than the well-known stabilized zirconia. The only difficulty which has prevented their use in high temperature fuel cells and gas sensors up to now is their ins tability against reduction at low oxygen partial pressures. In this ar ticle, we review the structural properties, thermal expansion, electri cal conductivity, thermodynamic stability, and surface properties of b ismuth oxide and solid solutions of bismuth oxide with face centred cu bic, rhombohedral, tetragonal or layer structures.