Composite of Ce0.8Gd0.2O2 − δ and GdBaCo2O5 + δ as oxygen separation membranes

A novel oxygen separation membrane using oxygen ions and a mixed oxygen ion-electron conducting CGO-GBCO (Ce0.8Gd0.2O2 − δ–GdBaCo2O5 + δ) dual phase composite has been proposed. The transport and surface exchange properties of the CGO-GBCO composite membrane are investigated as a function of oxygen partial pressure (OPP) over the OPP range of 10− 4 ≤ pO2/atm ≤ 0.21 at 1073 ≤ T/K ≤ 1323 using DC conductivity relaxation experiments. The surface exchange coefficient and the oxygen chemical diffusion coefficient of the composite are similar to those of the CGO-based composite membrane under oxidizing conditions. The characteristic thickness of the specimen, calculated from the oxygen chemical diffusion coefficient and surface exchange coefficient, LC = D̃/κ, is 0.25 mm at 1223 K. The thermally activated oxygen permeation flux monotonically increased with increasing oxygen chemical potential gradient, yielding a maximum of 0.28 cc/min·cm2 at air/He condition for the 0.62 mm-thick CGO-GBCO specimen at 1223 K. This value is an order of magnitude higher than that of GBCO at the same condition.