Mechanical stability of asymmetric Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) membrane tubes was improved by adaption of extrusion parameters and sintering conditions. The development of pore network and microstructure was investigated after long-term exposure at 850 degrees C for 25 weeks and compared to microstructure after manufacturing. Co-firing of coated supports was performed applying varying firing temperatures in order to analyze impact of grain size of the separation layer and support structure on oxygen permeation. The results revealed a remarkably improved long-term stability for supports manufactured using novel extrusion parameters and reduced firing temperatures. The oxygen permeation increased with rising grain size in the membrane layer, especially at high temperatures. An increased oxygen permeation at low temperature below 750 degrees C was found for membranes based on supports manufactured at adopted conditions.