The mixed conduction solid solution, Bi2O3-0.25Tb4O7, was studied by using impedance techniques and ionically blocking electrodes. These measurements confirmed the p-type electronic conductivity which had been suggested for this material. In air, at temperatures of between 600 and 900K, the ionic transference number ranged from 0.28 to 0.70. The total conductivity at 833K in air was 0.93S/m. The activation enthalpy for electronic conductivity varied from 77kJ/mol, in pure O2, to 83kJ/mol in an ambient with an O partial pressure of 0.0002atm. The electronic conductivity seemed to be a function of the sample geometry, and increased with decreasing cross-section to height ratio. The activation enthalpy for ionic conductivity was 110kJ/mol and was independent of the O partial pressure and of the sample geometry.

I.C.Vinke, B.A.Boukamp, K.J.De Vries, A.J.Burggraaf: Solid State Ionics, 1992, 57[1-2], 91-8