Oxygen-permeable ceramic membranes of 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. These materials possessed a purely cubic perovskite structure, with the exception of Ba0.5Sr0.5Co0.8Fe0.1M0.1O3−δ (M = Mn, Zr), in which minor impurities existed. The O permeability across these dense membrane disks was measured under an air/He oxygen partial pressure gradient at 973 to 1123K. The results demonstrated that the O permeation fluxes of the Ba0.5Sr0.5Co0.8Fe0.1M0.1O3−δ (M = Fe, Cr, Mn, Zr) membranes increased in the order: Fe (BSCFO) > Cr > Zr > Mn. The corresponding activation energies for O permeation in Ba0.5Sr0.5Co0.8Fe0.1M0.1O3−δ (M = Fe, Cr, Zr) membranes were calculated to be similar (53kJ/mol), and markedly lower than that (99kJ/mol) for Ba0.5Sr0.5Co0.8Fe0.1M0.1O3−δ (M = Mn) membrane. A good O permeation stability of the Ba0.5Sr0.5Co0.8Fe0.1M0.1O3−δ (M = Cr) membrane was achieved below 1123K. X-ray diffraction and differential thermal analysis experiments showed that the structural stability of BSCFO could be significantly improved when Fe ions in the BSCFO material were partially replaced by Cr, Mn or Zr ions.

Crystal Structure, Oxygen Permeability and Stability of Ba0.5Sr0.5Co0.8Fe0.1M0.1O3−δ (M = Fe, Cr, Mn, Zr) Oxygen-Permeable Membranes. H.Lu, J.Tong, Z.Deng, Y.Cong, W.Yang: Materials Research Bulletin, 2006, 41[4], 683-9