Self-standing, planar dual-phase oxygen transport membranes consisting of 70 vol% (ZrO2)(.89)(Y2O3)(.01)(Sc2O3)(.10) (10Sc1YSZ) and 30 vol% LaCr.85Cu.10Ni.05O3-delta (LCCN) were successfully developed and tested. The stability of the composite membrane was studied in simulated oxy-fuel power plant flue-gas conditions (CO2, SO2, H2O). The analyses of the exposed composites by X-ray diffraction (XRD), X-ray fluorescence (XRF), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and Raman spectroscopy revealed an excellent stability. Oxygen permeation fluxes were measured across 1000 mu m thick and 110 mu m thick self-supported 10Sc1YSZ-LCCN (70-30 vol%) membranes from 700 degrees C to 950 degrees C using air as the feed gas and N-2 or CO2 as the sweep gas. The 110 mu m thick membrane, prepared by tape-casting and lamination processes, showed oxygen fluxes up to 1.02 mL(N) cm(-2) min(-1) (950 degrees C, air/N-2). Both membranes demonstrated stable performances over long-term stability tests (250-300 h) performed at 850 degrees C using pure CO2 as the sweep gas.