Structure,Electrical Conducting and Thermal Expansion Properties of Ln_(0.6)Sr_(0.4)Co_(0.8)Fe_(0.2)

• 作 者: 徐庆
• 机 构: School of Materials Science and Engineering Wuhan University of Technology,,Wuhan 430070,China
• 出 处: Journal of Wuhan University of Technology(Materials Science
• 发表日期: 2008年03期
• 关键词: conducting lanthanide ceramics perovskite ceria nitrate glycine declined cubic e

Ln 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3 (Ln=La,Pr,Nd,Sm)perovskite-type complex oxides were synthesized using a glycine-nitrate process,and the structure,electrical conducting and thermal expansion properties of the resulting ceramics were examined with regard to the nature of the lanthanide cations.The results indicated that the La,Pr and Nd specimens had a rhombohedral symmetry,while an orthorhombic structure was determined for the Sm specimen.The pseudo-cubic lattice constant decreased with smaller lanthanide cations.It was found that the electrical conducting properties declined with decreasing lanthanide cation size.Fortunately, all the compositions remained rather high electrical conductivities exceeding 650Ω-1·cm-1 in the intermediate temperature range(600-800℃).An appreciable thermal expansion increase at high temperatures was detected for all the compositions.Decreasing the size of the lanthanide cations resulted in an increase of thermal expansion.With respect to the high electrical conductivities,the Ln 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3 oxides are considered to be acceptable as mixed conducting component in composite cathode designs together with doped ceria electrolytes.

Ln 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3 (Ln = La, Pr, Nd, Sm) perovskite-type complex oxides were synthesized using a glycine-nitrate process, and the structure, electrical conducting and thermal expansion properties of the resulting ceramics were examined with regard to the nature of the lanthanide cations. The results indicated that the La, Pr and Nd specimens had a rhombohedral symmetry, while an orthorhombic structure was determined for the Sm specimen. pseudo-cubic lattice constant decreased with smaller lanthanide cations. It was found that the electrical conducting properties declined with increasing lanthanide cation size. Fortunately, all the compositions are rather high electrical conductivities exceeding 650Ω-1 · cm-1 in the intermediate temperature range (600-800 ° C). An appreciable thermal expansion at high temperatures was detected for all the compositions. Decreasing the size of the lanthanide cations resulted in an increase of thermal expansion .With respect to the high electri cal conductivities, the Ln 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3 oxides are considered to be acceptable as a mixed conducting component in composite cathode designs together with doped ceria electrolytes.