Oxygen permeability and Faradaic efficiency of Ce0.8Gd0.2O2–δ–La0.7Sr0.3MnO3–δ composites

Composite Ce0.8Gd0.2O2−δ (CGO, solid electrolyte) and La0.7Sr0.3MnO3−δ (LSM, electronic conductor) ceramics were tested as dual-phase membranes for oxygen separation. Oxygen permeation through CGO–LSM composite ceramics containing similar percentages of both phases is limited by bulk ionic transport. In contrast to electronic transport, oxygen ion transport in these composites depends strongly on processing conditions, decreasing with interdiffusion of components. Oxygen ions are blocked by low ionic conductivity layers formed by diffusion of cations of LSM to the contacts between CGO grains. Testing of CGO–LSM membranes at high oxygen pressures (1–50 atm) showed that the composite ceramics are stable in these conditions and exhibit Wagner-type permeation fluxes.