DETERMINATION OF OXYGEN PERMEATION KINETICS IN A CERAMIC MEMBRANE-BASED ON THE COMPOSITION SRFECO0.5O3.25-DELTA

The oxygen permeation through an oxide ceramic membrane with bulk comp osition SrFeCo0.5O3.25-delta has been measured as a function of both t emperature and the oxygen pressure gradient across the membrane. The f orm of the pressure gradient dependence of the permeation indicates th at the oxygen transport in the membrane is dependent primarily on the bulk diffusion rate. Although the permeation experiments were carried out at temperatures within, or very close to, the range where SrFeCo0. 5O3.25-delta is stable as a pure single phase in air, the membrane was found to consist of SrFe1.5-xCoxO3.25-delta (x = similar to 0.42) tog ether with fractions of Sr(Co1-xFex)O2.5-delta perovskite and Co-Fe ox ide. Phase stability experiments indicate these phases formed as a sta ble assemblage when the membrane was densified at high temperature (10 90 degrees C) during final processing. The assemblage persists at the lower temperatures of the permeation experiments most likely because o f slow re-equilibration kinetics. (C) 1998 Elsevier Science B.V. All r ights reserved.