(Digital Presentation) New Magnetron Sputtering Fabrication Process for Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3- δ Miec Thin Film Membranes on Porous Support for Oxygen Permeation Applications

Mixed ionic electronic conductor (MIEC) membranes provide a great route for introducing oxygen to combustion and reforming processes of new fuels such as green ammonia. Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3- δ (BSCF) is known to be one of the most widely utilized perovskite material applied as oxygen transport membrane, as it possesses elevated oxygen permeability up to 7 ml(STP)·min -1 ·cm -2 at a temperature range of 850-900°C. Application of thin MIEC films of thicknesses of around 500 nm – 5 µm allow for reduction of Ohmic resistance for transport processes and sufficient oxygen permeation at lower temperatures as compared to bulk membranes, which is of great advantage with regard to materials stability and quality of sealing. However, fabrication techniques of thin MIEC membranes staunchly influence their phase purity. Crystallinity, microstructure and correlated oxygen diffusion properties as well as stability of membrane-substrate interfaces. Physical vapour deposition (PVD) such as magnetron sputtering (MS) is successfully applied to produce a dense and pinhole-free membrane with thicknesses ranging from 100 nm nanometer to a few micrometers. Challenges due to large size porosity of the ceramic substrate were addressed by tuning of the substrate porosity, ensuring formation of a continues layer and stability of the thin membranes. In this work, we report on the influence of the MS process parameters, as well as subsequent annealing techniques of both thermal annealing (TA) and line beam Laser annealing (LA) on the microstructure of a fabricated asymmetric membrane (AsM) consisting of BSCF thin membrane on a BSCF support wit tunable pore sizes. Oxygen permeability of the AsM was investigated at high temperatures (850-900 °C). For a substrate pore size of around 3 µm, BSCF membrane thicknesses of 1 to 5 µm could be applied for fabrication of AsM, resulting in a 2-fold increase of oxygen permeability ~5 ml.min -1 .cm -2 at a temperature of 900 °C as compared to a bulk BSCF support of ~2 mm thickness, whereas comparable oxygen permeation is already reached at a temperature of 700°C by the thin membrane. Contrariwise, the one with high porosity (~10 µm) required the deposition of thicker layers, which obstruct the oxygen diffusion and inhibited the permeation. The results have optimised sputtering process parameters, supports porosity and TA&/SLA parameters, are key factors for producing thin film membrane exhibiting high oxygen flux and good stability.