Effects of Nb and Sn co-doping on the structure and properties of SrCoO3-δ oxygen transport membranes

Abstract

The structure and oxygen permeability of SrCo0.9-xNb0.1SnxO3–δ (x = 0, 0.03, and 0.05) perovskite membranes were systematically investigated by co-doping the B-site of SrCoO3–δ oxide with Nb and Sn. Combined X-ray and neutron diffraction experiments showed that all materials crystallized in the tetragonal P4/mmm space group and that the crystal structures approached the ideal cubic perovskite structure with increasing Sn concentration. In addition, X-ray photoelectron spectra confirmed that Sn-doping increases the (Co, Nb, Sn)-O bond strengths. The impact of Sn-doping on the oxygen transport of dense SrCo0.9-xNb0.1SnxO3–δ membranes was also investigated, under air/He gradient, as a function of both temperature and membrane thickness. The results showed that the oxygen transport of SrCo0.9Nb0.1O3–δ is governed by oxygen ion diffusion, while the oxygen surface exchange reaction is the limiting process for the Sn-doped membranes, SrCo0.87Nb0.1Sn0.03O3–δ and SrCo0.85Nb0.1Sn0.05O3–δ.