Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-delta) (BSCF) hollow fibres are very attractive to deliver high oxygen fluxes at low manufacturing costs. These membranes efficiently separate oxygen from air via ionic diffusion, and have been exclusively prepared with sulphur containing binders, a vital ingredient to aggregate ceramic particles to shape hollow fibre geometries. Here we show that the choice of binder influences the stoichiometry of the crystal structure with the formation of non-ionic conduction domains, ultimately affecting oxygen ionic diffusion. Our synthesis method used sulphur free binders for the preparation of BSCF hollow fibres, resulting in an oxygen flux increase of 105% to 9.5 ml min(-1) cm(-2) at 950 degrees C. In addition, catalytic surface modification of the BSCF hollow fibres further increased oxygen fluxes to 14.5 ml min(-1) cm(-2). More importantly, oxygen fluxes significantly increased by a factor of 10 below 700 degrees C. thus reducing operating temperature requirements by 250 degrees C. (C) 2010 Elsevier By. All rights reserved.