Synthesis, characterization and evaluation of cation-ordered LnBaCo2O5+δ as materials of oxygen permeation membranes and cathodes of SOFCs

LnBaCo(2)O(5+delta) (Ln = La, Pr, Nd, Sm. Gd. and Y) was synthesized via an EDTA-citrate complexing process. The particular Ln(3+) dopant had a significant effect oil the oxide's phase structure/stability. oxygen content. electrical conductivity. oxygen permeability, and cathode performance. Stable, cation-ordered oxides with layered lattice structures were obtained with medium-sized Ln(3+) ions over a wide range of oxygen partial pressures, a property essential for applications as oxygen separation membranes and solid oxide fuel cell (SOFC) cathodes. PrBao(2)O(5+delta) demonstrated the highest oxygen flux (similar to 5.09 x 10(-7) mol cm(-2) s(-1) at 900 degrees C), but this value was still significantly lower than that of Ba(0.5)Sr(0.5)Co(0.8)Fe0.2O(3-delta) perovskite (similar to 3.1 X 10(-6) mol cm(-2) s(-1) at 900 degrees C. The observed difference was attributed to the Much longer diffusion distance through a polycrystalline inernbrane with a layered lattice structure than through Cubic perovskite because bulk diffusion was the rate-hiniting step of permeation. An area-specific resistance of similar to 0.213 Omega cm(2) was achieved at 600 degrees C with a PrBaCo2O5+delta cathode, SLIQOeStinO that the layer-structured oxides,vere promising alternatives to ceramic mernbranes for SOFC cathodes. (c) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.