Cerium/gadolinium oxide (CGO)-based ceramic ion conductive membranes (CICMs) have potential uses in catalytic membrane reactors (CMRs) and solid oxide fuel cells (SOFCs). A supercritical CO2 aided sol-gel process allowed the synthesis of CGO materials with the composition Ce0.9Gd0.1O1.95. The produced nanophase powders were non-agglomerated, with a controlled morphology, a high purity and a high specific surface area (> 100 m(2)/g). The CGO cubic crystalline phase has been obtained at temperatures < 300 degrees C, lower than those of conventional solid state chemistry routes. With respect to ionic oxygen transport, a high conductivity at intermediate temperature (2 x 10(-2) S cm(-1) at 600 degrees C), almost equivalent in dense and porous samples, has been obtained on sintered materials prepared from these powders. In relation to their porosity characteristics, a modelling approach successfully explained the high ionic oxygen transport of some specific porous samples. Future directions for preparing porous conductive ceramics well adapted to CMR or SOFC applications can be anticipated from this model. (c) 2005 Elsevier B.V. All rights reserved.