LnBaCo2O5+δ (Ln = La, Pr, Nd, Sm, Gd, and Y) was synthesized via an EDTA–

citrate complexing process. The particular Ln3+ dopant had a significant effect on

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 Ln3+ ions over a wide

range of oxygen partial pressures, a property essential for applications as oxygen separation membranes and solid oxide fuel cell cathodes. PrBaCo2O5+δ exhibited

the highest oxygen flux (about 5.09 x 10−7mol/cm2s at 900C), but this value was

still significantly lower than that of Ba0.5Sr0.5Co0.8Fe0.2O3−δ perovskite (about 3.1 x

10−6mol/cm2s at 900C). The observed difference was attributed to the much longer

diffusion distance through a polycrystalline membrane with a layered lattice

structure than through cubic perovskite because bulk diffusion was the rate-limiting

step of permeation. An area-specific resistance of about 0.213Ωcm2 was achieved

at 600C with a PrBaCo2O5+δ cathode, suggesting that the layer-structured oxides

were promising alternatives to ceramic membranes for SOFC cathodes.

Synthesis, Characterization and Evaluation of Cation-Ordered LnBaCo2O5+δ as

Materials of Oxygen Permeation Membranes and Cathodes of SOFCs. K.Zhang,

L.Ge, R.Ran, Z.Shao, S.Liu: Acta Materialia, 2008, 56[17], 4876-89