Dense BaCo0.7Fe0.2Ta0.1O3-delta (BCFT) perovskite membranes were successfully synthesized by a simple solid state reaction. In situ high-temperature X-ray diffraction indicated the good structure stability and phase reversibility of BCFT at high temperatures. The thermal expansion coefficient (TEC) of BCFT was determined to amount 1.02 x 10(-5) K-1, which is smaller than those of Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) (1.15 x 10(-5) K-1), SrCo0.8Fe0.2O3-delta (SCF) (1.79 x 10(-5) K-1), and BaCo0.4Fe0.4Zr0.2O3-delta (BCFZ) (1.03 x 10(-5) K-1). It can be seen that the introduction of Ta ions into the perovskite framework could effectively lower the TEC. Thickness dependence studies of oxygen permeation through the BCFT membrane indicated that the oxygen permeation process was controlled by bulk diffusion. A membrane reactor made from BCFT was successfully operated for the partial oxidation of methane to syngas at 900 degrees C for 400 h without failure and with the relatively high, stable oxygen permeation flux of about 16.8 ml/min cm(2). (C) 2009 American Institute of Chemical Engineers AIChE J, 56: 604-610, 2010