Crystal structure, oxygen permeability and stability of Ba0.5Sr0.5Co0.8Fe0.1M0.1O3−δ (M = Fe, Cr, Mn, Zr) oxygen-permeable membranes

Oxygen-permeable ceramic membrane materials of the Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCFO) and partially Fe-substituted Ba0.5Sr0.5Co0.8Fe0.1M0.1O3−δ (M = Cr, Mn, Zr) were synthesized by solid-state reaction method. These materials possess purely cubic perovskite structure with the exception of Ba0.5Sr0.5Co0.8Fe0.1M0.1O3−δ (M = Mn, Zr), in which minor impurities exist. Oxygen permeability across these dense membrane disks were measured under an air/He oxygen partial pressure gradient in the temperature range of 973–1123 K. The results demonstrated that the oxygen permeation fluxes of the Ba0.5Sr0.5Co0.8Fe0.1M0.1O3−δ (M = Fe, Cr, Mn, Zr) membranes increased in the following order: Fe (BSCFO) > Cr > Zr > Mn. The corresponding activation energies for oxygen permeation of Ba0.5Sr0.5Co0.8Fe0.1M0.1O3−δ (M = Fe, Cr, Zr) membranes were calculated to be similar (53 ± 4 kJ/mol), which was remarkably lower than that (99 ± 3 kJ/mol) of Ba0.5Sr0.5Co0.8Fe0.1M0.1O3−δ (M = Mn) membrane. In addition, good oxygen permeation stability of the Ba0.5Sr0.5Co0.8Fe0.1M0.1O3−δ (M = Cr) membrane was achieved at the temperature lower than 1123 K. The X-ray diffraction (XRD) and differential thermal analysis (DTA) experiments showed that the structural stability of BSCFO could be significantly improved when Fe ions in the BSCFO material were partially substituted by Cr, Mn or Zr ions.