A surface modified La0.6Sr0.4Co0.2Fe0.8O3-delta sandwich ceramic membrane with ultrathin dense layer, 4 mu m, has been developed for highly efficient oxygen separation. Compared with conventional dense disks, the new structure significantly increases oxygen permeation flux by a magnitude. This impregnated sandwich structure offers the highest performance of oxygen separation up to now due to the reduced thin dense layer and enhanced surface exchange kinetics. (C) 2014 Elsevier B.V. All rights reserved.