Yttrium doped BSCF membranes for oxygen separation

► Yttrium substitution for iron of 2.5 mol% in BSCF improved oxygen fluxes by as much as 160%. ► Excess doping formed a non-perovskite which was not oxygen-permeable. ► Increased oxygen fluxes due to yttrium substitution were correlated oxygen vacancy and the mobility of oxygen ions. ► Yttrium substitution resulting in increased oxygen vacancies and crystal lattice.