The oxygen transport through supported membranes made of Ba0.5Sr0.5Co0.8Fe0.2O3-delta is investigated. For this, disc shaped membranes were manufactured by means of tape casting, consisting of a gastight layer with varying thickness (0.9 mm-20 mu m) and a porous support with varying porosity (34%/41%). The sample's microstructure was analyzed using SEM and X-ray computer tomography and by this means characteristic values (i.e., porosity, tortuosity, and specific surface area) were determined. A modeling concept was developed based on literature approaches, extending the Wagner equation for bulk transfer with a geometrical factor beta for the characteristic thickness accounting active supports and different surface microstructures. The results were compared with permeation measurements of samples under varying operation conditions (i.e., sweep flow rate, and feed gas). As a result, good agreement between model and measurement in case of a constant porosity is found for characteristic thicknesses L-c as reported in literature. However, calculations with varying porosity show indistinguishable results, indicating an underestimate of the geometric factor versus the influence of the characteristic thickness L-c Also, significant limitations of the oxygen permeation due to surface exchange and concentration polarization in the support is shown. (C) 2013 Elsevier B.V. All rights reserved.