EFFECT OF SURFACE STATES ON OXYGEN PERMEABILITY OF PEROVSKITE-TYPE OXIDE DENSE DISK

摘要

In order to collect information about the contribution of the surface reaction and bulk diffusion rates in oxygen permeation through mixed ionic-electronic conductive perovskites, La_(0.1)Sr_(0.9)Co_(0.9)Fe_(0.1)O_(3-δ) dense disks with different surface areas (roughness) and thicknesses were prepared and their oxygen permeability was measured. The oxygen permeation rate through the 1 mm-thick membrane was little dependent on the surface area below 700°C, indicating that oxygen permeation is almost exclusively controlled by the diffusion of oxide ions in the membrane. Above 750°C, on the other hand, the oxygen permeation rate increased with increasing surface area and therefore the rates of both diffusion and surface reactions contributed to the oxygen permeation flux; the contribution of the surface reaction became more significant with increasing temperature. The effect of surface area on the oxygen permeation flux through thinner membrane was more prominent than that through thicker membrane.