The hydrogen permeability of SrCe0.95EU0.05O3-delta was studied as a function of temperature, hydrogen partial pressure (P-H2) gradient, and water vapor partial pressure (P-H2O) gradient. The effect of the microstructure on hydrogen permeability through a 1.72 mm thick membrane was investigated. The ambipolar conductivity calculated from hydrogen permeation fluxes showed the same P-O2 and P-H2 dependence as the electronic conductivity, for the experimental conditions. The small grained membrane showed higher hydrogen permeability when compared with the larger grained membrane over the entire temperature range investigated. (c) 2005 Springer Science + Business Media, Inc.