Oxygen permeation characteristics of sol-gel derived barium-substituted strontium ferrite membranes

The pervoskite-type oxides have received attention due to their potential applications in catalysis, solid oxide fuel cells, gas sensors, and gas separable membranes. In view of their importance in oxygen separation from air, BaxSr1-xFeO3- (0x1.0) samples have been synthesized by sol-gel process and investigated with regard to phase(s), oxygen permeation, and electrical conductivity. These compounds possess at room temperature, a perovskite-type cubic, mixture of rhombohedral and hexagonal, and hexagonal phase(s) depending upon the composition 0x0.94, x=0.96-0.98, and x=1.0, respectively. The barium incorporation causes initially enhancement but decrease in electrical conductivity above x=0.94. Above 800 degrees C, all the compositions exhibit a stable cubic phase. The compacts made in the form of discs serve as stable oxygen permeable membranes displaying flux density (JO2) of similar to 2.45-3.58mL/cm(2).min at 1000 degrees C. A good correlation has been demonstrated between the oxygen permeation and the electrical conductivity data. The maximum values of JO2 and conductivity correspond to BaxSr1-xFeO3- (x=0.94) with a perovskite-type cubic structure. Hence, this membrane is quite suitable for oxygen separation technology.