Effect of iron substitution content on structure, thermal expansion behavior and electrochemical properties of La sub(0.5)Ba sub(0.5)Co sub(1-y)Fe sub(y)O sub(3- delta )

• Published in: International journal of hydrogen energy Vol. 36; no. 21; pp. 13850 - 13857
• Main Authors: Li, Xiangnan, Jiang, Xuening, Pang, Shengli, Wang, Qian, Su, Zhixian, Zhang, Qingyu
• Format: Journal Article
• Language: English
• Published: 01.10.2011
• Subjects: Cathodes; Conductivity; Defects; Ionic diffusion; Iron; Oxides; Oxygen content; Thermal expansion
• ISSN: 0360-3199
• DOI: 10.1016/j.ijhydene.2011.07.083

Cubic perovskite oxides La sub(0.5)Ba sub(0.5)Co sub(1-y)Fe sub(y)O sub(3- delta ) (LBCF-y) with Fe content y = 0.1-0.7 were synthesized by sol-gel method and were studied with respect to their oxygen content, defect chemistry, thermal expansion behavior, and electrical and electrochemical properties. LBCF-y had increased oxygen content and cell volumes with higher Fe content. The chemical defects at B-sites of LBCF-y are Fe super(4+), Co super(4+) and Co super(3+) ions for y = 0.1-0.3, and Fe super(4+), Fe super(3+) and Co super(3+) ions for y = 0.5 respectively. Thermal expansion coefficients of LBCF-y oxides firstly increased to a maximum at y = 0.3 then decreased gradually with bigger y. Conductivities of LBCF-y decreased with higher Fe content, and the maximum conductivity was 800 S cm super(-1) at 500 K for LBCF-0.1 sample. Fe substitutions for Co in LBCF-y cathodes increase the high-frequency resistance associated with oxygen ionic diffusion process while hardly influence the low-frequency gas diffusion process. Very low area-specific resistances, 0.1 [omega] cm super(2) at 923 K, were obtained for LBCF-y (y = 0.1-0.7) oxides, demonstrating their potential applications as cathode materials for intermediate-temperature solid oxide fuel cells.