Effect of CuO additive on the sintering and performance of niobium-doped strontium cobaltite as oxygen separation membranes

In this work, the effects of CuO addition on sintering behavior, crystal structure and the oxygen permeation of SrCo0.9Nb0.1O3-delta (SCN) membranes have been investigated. XRD characterization demonstrated that copper could incorporate into the perovskite lattices with certain solubility dependent on temperature. Small amount of CuO (5 wt.%) successfully reduced the sintering temperature of the SCN membrane by 180 degrees C. A relative density of 95.4% was reached for the membrane with 5 wt.% CuO additive after sintering at 1000 degrees C. The promoting effect on sintering is likely associated with liquid assisted sintering. The incorporation of copper into the SCN lattice has minimal effect on the membrane sintering but a significant effect on the membrane integrity. As compared to the single-phase SCN membranes, the introduction of CuO as a sintering aid does not affect the electronic conductivity of the membrane between 700 and 900 degrees C, but the oxygen permeability is slightly reduced. Permeation study of the membranes of 0.9 mm thickness demonstrated oxygen fluxes of 1.5, 1.4, 1.3 and 1.2 ml cm(-2) min(-1) [STP] at 800 degrees C for the membranes containing 0 (pure SCN), 1,3 and 5 wt.% CuO, respectively. The results suggest that the introduction of CuO as a sintering aid had a more significant effect on the oxygen surface exchange kinetics than on the oxygen bulk diffusion rate. (C) 2010 Elsevier B.V. All rights reserved.