This study examines membrane synthesis, structural stability, permeation properties, and long-term permeation stability of a new dense dual-phase membrane of composition La0.85Ce0.1Ga0.3Fe0.65Al0.05O3-delta (LCGFA)-carbonate for high temperature CO2 separation. Porous ceramic supports made by sintering pressed powder at a temperature below its densification temperature resulted in a desired support with an open porosity ranging between 40 and 50%. The dual-phase membranes was prepared by direct infiltration of the ceramic supports in molten carbonate at 600 degrees C, resulting in a four order of magnitude decrease in permeance when compared to the support. LCGFA-carbonate membranes are stable when exposed to gases ranging from gas mixtures containing N-2 and various concentrations of CO2 to simulated syngas, and exhibit a stable long term CO2 permeation flux of 0.025 mL.min(-1).cm(-2) for more than 275 h at 900 degrees C. The CO2 permeation results show exponential dependence to increasing system temperature as well as a linear dependence to logarithmic change in CO2 partial pressure gradients across the membrane in the CO2 pressure range studied. (C) 2014 Elsevier B.V. All rights reserved.