Effect of Bi doping on the performance of dual-phase oxygen-permeable membranes

Doping of cations is an effective method to adjust the properties of oxygen permeable membrane materials. Eight dual-phase oxygen-permeable membrane materials 75 wt% Ce0.8Sm0.2-xBixO2-delta-25 wt% Sm0.6Sr0.4Al0.3Fe0.7O3-delta (CSBx-SSAF, x = 0, 0.05, 0.1, 0.15) and 75 wt% Ce0.8Sm0.2-xBixO2-delta-25 wt% Sm0.6Sr0.4Cu0.2Fe0.8O3-delta (CSBx-SSCF, x = 0, 0.05, 0.1, 0.15) prepared by solid state reaction method were investigated to explore the effect of Bi doping. Properties of the membrane materials, including sintering temperature, crystal structure, microstructure, thermal expansion coefficient, total conductivity and oxygen permeation flux, were explored. Study results show that Bi doping increases the thermal expansion coefficients and decreases the sintering temperatures and total conductivities of the dual-phase membranes as well as the oxygen permeation fluxes for the CSBx-SSAF series of membranes. However, the incorporation of Cu is beneficial to the membrane performance improving with the increase of Bi doping amount. EDS map analysis illustrates that the doped Bi elements partially enter the perovskite phase, partially form compound rich in Sr and Bi, and a few enter the fluorite phase