SrZr0.2Ce0.8-xEuxO3-delta (x = 0.1 and 0.15) membranes were investigated for their hydrogen permeation properties as a function of membrane thickness, from 17 to 50 mu m. Membrane permeation flux was proportional to [P-H2](1/4) matching Norby and Larring's model when protons and electrons are the dominating defects. The observed inverse linear dependence of flux with membrane thickness indicates bulk diffusion is the rate-limiting factor for hydrogen permeation. After correcting for water formation, higher Eu doping in the membrane was confirmed to result in greater hydrogen flux, consistent with our previous conductivity studies. A H-2 flux of 0.35 cc/min cm(2) was achieved for 17 mu m thickness SrZr0.2Ce0.7Eu0.1O3-delta membrane at 900 degrees C and 100% H-2 in the feed gas. However, taking observed water vapor formation into consideration, a maximum H-2 flux of 0.50 cc/min cm(2) was achieved under the same conditions. (C) 2009 Elsevier B.V. All rights reserved.