The electronic conductivity of Ce0.8PrxTb0.2−xO2−δ (x = 0, 0.05, 0.10, 0.15, 0.20) was determined in the oxygen activity range aO2 ≈ 103 – 10−17 at 700–900°C by Hebb-Wagner polarization. The electronic conductivity of all the Ce0.8PrxTb0.2−xO2−δ compositions was significantly enhanced as compared to that of Ce0.9Gd0.1O1.95−δ, and was found to increase with increasing Pr/Tb ratio. The oxide ion mobility in Ce0.8PrxTb0.2−xO2−δ is similar to that in Ce1−2δGd2δO2−δ at the same oxygen vacancy concentration. Based on the measured ionic and electronic conductivities, fluxes through thin film Ce0.8PrxTb0.2−xO2−δ membranes were calculated. Calculated fluxes exceed 10 Nml min−1 cm−2 under oxyfuel relevant conditions (T = 800°C, aO2,permeate side = 10−3). Hence, in terms of transport properties, these materials are promising for this application. Interference between the ionic and electronic flows has a significant positive effect on the deliverable oxygen flux, as evaluated for Ce0.8Pr0.2O2−δ.1. © 2012 The Electrochemical Society. All rights reserved.