Effects of iron content on the structural evolution, electrical properties and thermochemical stability of BaCo 0.9Lx Fe x Nb 0.1 O 3Ld ceramic membrane Ji Zhang a , Hailei Zhao a,c, *, Yuan Li a , Nansheng Xu a , Weizhong Ding b , Xionggang Lu b , Fushen Li a,c a Department of Inorganic Nonmetallic Materials, University of Science and Technology Beijing, Beijing 100083, China b School of Materials Science and Engineering, Shanghai University, Shanghai 200072, China c Beijing Key Lab. of New Energy Material and Technology, Beijing 100083, China article info Article history: Received 27 July 2009 Received in revised form 15 October 2009 Accepted 28 October 2009 Available online 14 November 2009 Keywords: Oxygen permeation material Perovskite Fe-doping Structure stability abstract Cubic perovskite oxygen permeation materials BaCo 0.9x Fe x Nb 0.1 O 3d (BCFN, x ¼ 0.1–0.7) are prepared by the conventional solid state reaction process. The crystal structure develop- ment, structural stability, electrical conductivity and oxygen permeation flux are investigated. The introduction of iron makes the formation of cubic perovskite structure for BCFN materials much easier. BCFN exhibits a p-type semiconductor and obeys the thermally activated small polarons hopping mechanism. The electrical conductivity of BCFN increases with increasing temperature and decreases with the Fe-doping concen- tration. The incorporation of Fe decreases slightly the oxygen permeability of BCFN membranes, but enhances significantly the structure stability of the oxygen permeation membrane in reducing atmosphere. A high oxygen permeation flux of 1.7 ml cm 2 min 1 at 900  C through 1 mm densified membrane under air/helium condition is obtained for the composition of BaCo 0.6 Fe 0.3 Nb 0.1 O 3d . ª 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved. 1. Introduction Hydrogen is thought to be the future energy carrier in the 21st century, and hydrogen can be produced from various materials such as water, fossil fuels, biomass and some industrial chemical by-products [1–4]. Among them, partial oxidation of methane (POM) by using mixed ionic and electronic conducting (MIEC) membrane is regarded as an efficient and low cost way to produce hydrogen [5]. In the whole hydrogen producing process, the performance of MIEC membrane is the key point. A suitable membrane for practical use should possess not only considerably high permeability, but also sustainable structural stability to withstand the harsh working conditions (syngas, carbon oxide, water vapor, etc.) [6]. It was found that mixed conductors with high oxygen permeability usually have perovskite structure and contain cobalt, such as SrCoO 3d and BaCoO 3d based perovskites. However cobalt-containing oxides always exhibited limited chemical and structural stability in reducing environment. For example, Pei et al. [7] found that because of the lattice expansion mismatch of reducing side and oxidizing side of the membrane, the failure of the SrCo 0.8 Fe 0.2 O 3d membrane occurred shortly after the initiation of the partial oxidation of * Corresponding author. Department of Inorganic Nonmetallic Materials, University of Science and Technology Beijing, Beijing 100083, China. Tel./fax: þ86 10 82376837. E-mail address: hlzhao@mater.ustb.edu.cn (H. Zhao). Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he 0360-3199/$ – see front matter ª 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijhydene.2009.10.101 international journal of hydrogen energy 35 (2010) 814–820