Oxygen permeation measurements were performed on planar membranes of (La0.8Sr0.2)(0.95)Cr0.5Fe0.5O3 - (delta) (LSCrF)-SC0.198Ce0.012Zr0.789O1.90 (10Sc1CeSZ) with various exchange layers and membrane thicknesses. Addition of a fuel side exchange layer capable of nickel exsolution provided approximately twice the performance compared with no exsolved catalyst for a 300 pm thick membrane at 900 degrees C. Use of a 20 Earl thick membrane with a porous support structure produced a further 7 fold improvement in oxygen flux at 900 degrees C to yield 3.54 ml cm(-2) min(-1). (C) 2016 The Authors. Published by Elsevier B.V.