The Ba0.5Sr0.5Co0.8Fe0.2O3−δ exhibited high oxygen permeability, and is thus considered for gas separation (oxygen transport membrane) in zero-emission power plants. An investigate was made here of the influence of membrane processing upon microstructure and oxygen permeation. Pure-phase Ba0.5Sr0.5Co0.8Fe0.2O3−δ powder was synthesized using a modified Pechini method. For comparison, commercially available powder was also used, synthesized by a solid-state reaction. Disk-shaped membranes of various microstructures, i.e. closed porosities and grain sizes, were prepared by uniaxial pressing and sintering of the powders processed in different ways. The powders and membranes were characterized by methods including BET, SEM, XRD, and DSC. The microstructures obtained by different sintering conditions were investigated by SEM and TEM. Sintering at 1150C led to incongruent melting of BSCF indicated by DSC. The liquid phase appeared at three-phase boundaries grain–grain–air and consisted of nearly pure cobalt oxide with small impurities of barium and strontium detected by TEM/EDX analysis. Oxygen permeation of the membranes was measured in an air/Ar gradient depending on temperature and membrane microstructure. The closed porosity of different processed membranes was varied between 2 and 15% with uniform grain sizes in the range of approx. 10 μm. The average grain size was increased from 10 to 45 μm by increasing the sintering temperature. Neither porosity nor the grain size significantly influenced the oxygen permeation rate of 1-mm-thick disks in the investigated parameter range.

Influence of Sintering Conditions on Microstructure and Oxygen Permeation of Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) Oxygen Transport Membranes. S.Baumann, F.Schulze-Küppers, S.Roitsch, M.Betz, M.Zwick, E.M.Pfaff, W.A.Meulenberg, J.Mayer, D.Stöver: Journal of Membrane Science, 2010, 359[1-2], 102-9