Performance of functional perovskite membranes for oxygen production

In this paper, the influence of composition, thickness, porous activation layers, and measurement conditions on the oxygen permeation rates of mixed ion electron conducting membranes is discussed. To this end, functional membranes, rather than pressed pellets, with an effective surface area of ∼18 cm2 and a thickness of ∼200 μm with the compositions SrCo0.8Fe0.2O3−δ, Sr0.5Ba0.5Co0.8Fe0.2O3−δ, Sr0.8La0.2Co0.8Fe0.2O3−δ, Ba0.8La0.2Co0.8Fe0.2O3−δ, and Sr0.4La0.6Co0.2Fe0.8O3−δ, have been prepared and tested. The highest oxygen fluxes measured for the former two compounds under non-reducing conditions were ∼13 N ml cm−2 min−1. The coefficient of thermal expansion (CTE) was shown to be strongly dependent on the atmosphere. In a helium atmosphere, SrCo0.8Fe0.2O3−δ and Sr0.8La0.2Co0.8Fe0.2O3−δ show a negative CTE over a limited temperature range due to the phase transition from a brownmillerite to a perovskite phase. Membrane degradation due to kinetic demixing is an important issue in the long-term stability of Sr0.5Ba0.5Co0.8Fe0.2O3−δ.