Performance of Zinc-doped Perovskite-type Cathodes at Intermediate Temperatures and Under Carbon Dioxide Atmosphere

Zinc-doped (BaSr)FeO3-δ perovskite-type membranes were found to exhibit an excellent long-term stability at high and intermediate temperatures under an oxygen partial pressure gradient. With carbon dioxide as sweep gas, the oxygen permeation diminishes almost completely. By X-ray diffraction a phase mixture of hexagonal, tetragonal and cubic perovskite with a (Ba0.4{plus minus}0.1Sr0.6{plus minus}0.1)CO3 layer and some zinc oxide was found. Transmission electron microscopy showed that the dense perovskite membrane is decomposed into phases with different morphologies accompanied by pore and crack formation in a surface layer of 5 µm. After switching to helium as the sweep gas, a hexagonal perovskite phase is still present, which reduces the oxygen permeation flux. A short heating to 950 {degree sign}C regenerates the oxygen permeation flux. The appearance of the carbonate structure leads to a breakdown of the oxygen permeation ability, but the effect of the carbon dioxide is totally reversal after a short high temperature treatment.