Oxygen permeation through short-circuited yttria-stabilized-zirconia membranes

Short-circuited yttria-stabilized-zirconia (YSZ) membranes were used as a model to study oxygen permeation through mixed-ionic-electronic-conductors(MIECs). The complete separation of the electronic and ionic contributions to the net current made it possible to experimentally test existing theories of oxygen permeation. Under all experimental conditions examined, the oxygen flux through dense membranes was found to be lower than values calculated using the Wagner equation, even in the bulk diffusion limited case. This result was attributed to the non-negligible contribution of the surface exchange process, which became the ultimate limiting step at low oxygen pressures and at high temperatures.