Ionic and electronic conduction of oxygen ion conductors in the Bi2O3−Y2O3 system

The ionic conduction of sintered samples of Bi₂O₃?Y₂O₃ containing 20–30 mol% Y₂O₃ has been investigated by means of ac conductivity experiments and EMF measurement of an oxygen concentration cell using the specimen tablet as electrolyte. Ac conductivity was measured at a frequency of 10 kHz under oxygen partial pressures ranging from 1 to 10^-21 atm. The results show that these materials possess high ionic conduction. The conductivities for samples containing 22.5–30 mol% Y₂O₃ are many times higher than those of stabilized zirconia-based solid electrolyte at corresponding temperatures. The ratio of E_meas./E_calc. of an oxygen concentration cell Pt∣O₂(air)∣Bi₂O₃?Y₂O₃∣O₂(pure oxygen)∣Pt is close to 1 which shows that the materials containing 22.5 to 30 mol% Y₂O₃ are nearly pure ionic conductors. The p-type conductivity is negligible at higher P_O2 values. The n-type conduction for a sample containing 27.5 mol% Y₂O₃ was investigated using the Coulomb titration technique in which the following cell was used: Pt Rh∣O₂(air)∣Bi₂O₃?Y₂O₃∣[O]_sn∣W.log P_é=-767000/T+665. P_é is equal to 2.6×10^-61 atm at 800°C. The n-type conductivity is also very small. Thus these materials are good oxygen ionic conductors.