Electrical properties and thermal expansion of cobalt doped apatite-type lanthanum silicates based electrolytes for IT-SOFC |
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| Authors: | Qingle Shi Lihua Lu Hongjian Jin Hua Zhang Yanwei Zeng |
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| Affiliation: | 1. Institute of High-Temperature Electrochemistry, 20 Academicheskaya St., 620137 Ekaterinburg, Russia;2. Ural Federal University, 19 Mira St., 620002 Ekaterinburg, Russia;1. Department of Applied Chemistry, Graduate School of Engineering, University of Hyogo, Himeji, Hyogo 671-2201, Japan;2. Graduate School of Material Science, University of Hyogo, 3-2-1, Kouto, Kamigori, Ako, Hyogo 678-1297, Japan;3. Synchrotron Radiation Nanotechnology Center, University of Hyogo, 1-490-2, Kouto, Shingu, Tatsuno, Hyogo 679-5165, Japan;4. Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1, Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan;5. SPring-8 Service Co., Ltd., 1-20-5, Kouto, Shingu, Tatsuno, Hyogo 679-5165, Japan |
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| Abstract: | The thermal expansion and conductivities have been investigated for Co3+ doped lanthanum silicates. The apatite-type lanthanum silicates with formula La10Si6?xCoxO27?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 La10Si6?xCoxO27?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 La10Si5.2Co0.8O26.6 exhibits the highest conductivity of 3.33 × 10?2 S/cm at 800 °C. When x ≤ 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 ≤ 1.5) reduced the number of interstitial oxide ions and decreased the conductivity. |
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