Oxygen permeation properties of Bi-doped La0.8Sr0.2FeO3-5 planar ceramic membranes at intermediate temperature

Ceramic oxygen permeable membranes (COPMs) have attracted attention as a "next generation" technology for oxygen separation. However, developing new oxygen permeable membrane materials with high oxygen permeability at an intermediate operating temperature is still challengeable. In this work, a series of perovskite La0.8-xBixSr0.2FeO3-5 (LBSF, x = 0.0, 0.2, 0.3 and 0.4) oxides were synthesized and used as the oxygen permeation membrane materials. The phase structure, electrical conductivity, chemical compatibility with 3 mol% yttria-stabilized zirconia (3YSZ), O2 temperature programmed desorption (O2-TPD) have been evaluated. An asym-metric three-layer structure with "porous-transition-dense" was developed by tape casting, hot-pressing and co-sintering technology. The membrane consists of a porous 3YSZ support layer, a 3YSZ-LBSF transition layer and a dense LBSF functional layer. The oxygen permeability was tested by a new designed electrochemical device based on the limit current method. The best oxygen permeability was found in the composition of La0.4Bi0.4Sr0.2FeO3-5 measured at an intermediate temperature of 800 degrees C with 20% oxygen partial pressure, which could reach 1.13 mL min-1 cm-2. No obvious degradation was observed on the three-layers La0.4Bi0.4Sr0.2FeO3-5 membrane after a stability test at 800 degrees C for 150 h under 1.6 V and subsequent 11 times thermal cycling between 700 degrees C and 800 degrees C. The membrane exhibited excellent long-term stability and thermal cycling stability.