Electrical properties and thermal expansion of cobalt doped apatite-type lanthanum silicates based electrolytes for IT-SOFC

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• 作者：Qingle Shi ; Lihua Lu ; Hongjian Jin ; Hua Zhang ; ^{huazhang@njut.edu.cn} ; ^{llh0727@163.com} ; ^{shiqingle1219@163.com} ; Yanwei Zeng
• 关键词：A. Oxides ; B. Sol&ndash ; gel chemistry ; C. Impedance spectroscopy ; D. Ionic conductivity ; D. Thermal expansion
• 刊名：Materials Research Bulletin
• 出版年：2012
• 期刊代码：60_00255408
• 类别：ms
• 出版时间：March, 2012
• 卷：47
• 期：3
• 页码：719-723
• 文件大小：755 K

摘要

The thermal expansion and conductivities have been investigated for Co³⁺ doped lanthanum silicates. The apatite-type lanthanum silicates with formula La₁₀Si_6鈭?em>xCo_xO_27鈭?em>x/2 (x = 0.2, 0.4, 0.6, 0.8, 1.0, 1.5) were synthesized by sol-gel process. The thermal expansion coefficient (TEC) of La₁₀Si_6鈭?em>xCo_xO_27鈭?em>x/2 was improved with increasing cobalt content because of the lower valence and larger radius of Co³⁺ ion compared to Si⁴⁺. Analysis of AC impedance spectroscopy showed that conductivity increased first and then decreased with increasing cobalt content. There is an optimum doping amount of cobalt and La₁₀Si_5.2Co_0.8O_26.6 exhibits the highest conductivity of 3.33 脳 10^鈭? S/cm at 800 掳C. When x 鈮?#xA0;0.8, the local distortion caused by doping with Co³⁺ can significantly affect the oxygen channels and assist the migration of the interstitial oxide ions, resulting in the improvement of ionic conductivity. However, excess Co³⁺ dopant (0.8 < x 鈮?#xA0;1.5) reduced the number of interstitial oxide ions and decreased the conductivity.