The CO2 permeation of composite membranes obtained by impregnation of molten alkaline carbonates into a Gd-doped curia ceramic skeleton was tested using several gas mixtures with up to 50 vol% CO2 as feed gas and Ar in the membrane permeate side. Experiments performed in the 550-850 degrees C temperature range showed high permeation rates reaching 06 cm(-3) min(-1) cm(-2) at 850 degrees C for the higher CO2 content. These values exceed those often reported for similar membranes and conditions. Furthermore, the characterization of the ceramic skeletons and composite membranes by impedance spectroscopy (in an at low temperature) could be used to estimate the temperature where dual oxide and carbonate ionic transport are balanced (around 800 degrees C). The inherent shift in the CO2 permeation activation energy is shown to match closely this prediction. (C) 2014 Elsevier B.V. All rights reserved.