Stabilization of a Complex Perovskite Superstructure under Ambient Conditions: Influence of Cation Composition and Ordering, and Evaluation as an SOFC Cathode

详细信息    查看全文

• 作者：A. Demont ; M. S. Dyer ; R. Sayers ; M. F. Thomas ; M. Tsiamtsouri ; H. N. Niu ; G. R. Darling ; A. Daoud-Aladine ; J. B. Claridge ; M. J. Rosseinsky
• 刊名：Chemistry of Materials
• 出版年：2010
• 出版时间：December 28, 2010
• 年：2010
• 卷：22
• 期：24
• 页码：6598-6615
• 全文大小：1704K
• 年卷期：v.22,no.24(December 28, 2010)
• ISSN：1520-5002

文摘

Ba_1.6Ca_2.3Y_1.1Fe₅O₁₃ is an Fe³⁺ oxide adopting a complex perovskite superstructure, which is an ordered intergrowth between the Ca₂Fe₂O₅ and YBa₂Fe₃O₈ structures featuring octahedral, square pyramidal, and tetrahedral B sites and three distinct A site environments. The distribution of A site cations was evaluated by combined neutron and X-ray powder diffraction. Consistent with the Fe³⁺ charge state, the material is an antiferromagnetic insulator with a Nel temperature of 480−485 °C and has a relatively low d.c. conductivity of 2.06 S cm⁻¹ at 700 °C. The observed area specific resistance in symmetrical cell cathodes with the samarium-doped ceria electrolyte is 0.87 Ω cm² at 700 °C, consistent with the square pyramidal Fe³⁺ layer favoring oxide ion formation and mobility in the oxygen reduction reaction. Density functional theory calculations reveal factors favoring the observed cation ordering and its influence on the electronic structure, in particular the frontier occupied and unoccupied electronic states.