Effect of Fe content on properties of Ba₀.₅Sr₀.₅Co_xFe _1-xO_3-δ mixed conducting membranes

Mixed oxygen-ionic and electronic conducting Ba₀.₅Sr₀.₅Co_xFe _1-xO_3-δ (BSCFO) oxide powders were synthesized by using a combined EDTA-citrate complexing method. The effect of Fe content on the properties of the material, such as phase structure, phase stability, thermochemical stability and oxygen permeability, were investigated with combined XRD, O₂-TPD, H₂-TPR techniques and oxygen permeation measurement. For the material under investigation (cursive Greek chi = 0.2∼0.8), they all demonstrate the pure phase of cubic perovskite structure at high temperature and within the oxygen partial pressure of 2.13 × 10⁴∼0.1 Pa. The increase in Fe content is beneficial to the phase stability of BSCFO at lower temperature. However, the oxygen permeability of the material decreases with the increase of Fe content, being likely due to the increase in surface exchange kinetics of the membrane in the rate determination of the oxygen permeation process with the increase of Fe content.