Systematic investigation on new SrCo1-yNbyO3-δ ceramic membranes with high oxygen semi-permeability

SrCo1-yNbyO3-delta (y = 0.025-0.4) were synthesized for oxygen separation application. The crystal structure, phase stability, oxygen nonstoichiometry, electrical conductivity, and oxygen permeability of the oxides were systematically investigated. Cubic perovskite, with enhanced phase stability at higher Nb concentration, was obtained at y = 0.025-0.2. However, the further increase in niobium concentration led to the formation of impurity phase. The niobium doping concentration also had a significant effect on electrical conductivity and oxygen permeability of the membranes. SrCo0.9Nb0.1O3-delta exhibited the highest electrical conductivity and oxygen permeability among the others. It reached a permeation flux of similar to 2.80 x 10(-6) mol cm(-2) s(-1) at 900 degrees C for a 1.0-mm membrane under an air/helium oxygen gradient. The further investigation demonstrated the oxygen permeation process was mainly rate-limited by the oxygen bulk diffusion process. (c) 2008 Elsevier B.V. All rights reserved.