Journal of the Korean Electrochemical Society (전기화학회지)

The Korean Electrochemical Society (한국전기화학회)
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Synthesis and Electrochemical Properties of (La0.6Sr0.4)(Co0.2Fe0.8)O3 cathode for SOFC on pH Control Using Modified Oxalate Method

Modified Oxalate Method 의해 합성한 SOFC용(La0.6Sr0.4)(Co0.2Fe0.8)O3 Cathode의 pH 변화에 따른 특성

  • Published : 2007.11.28
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Abstract

The LSCF cathode far Solid Oxide Fuel Cell was investigated to develop high performance unit cell at intermediate temperature by modified oxalate method with different electrolytes and different pH. The LSCF powders employed La, Sr, Co and Fe oxides, oxalic acid, ethanol and $NH_4OH$ solution were synthesized with pH controlled as 2, 6, 7, 8, 9 and 10 at $80^{\circ}C$ Single crystalline phase was obtained from pH $2{\sim}9$. on the other hand, $La_2O_3$ appeared from pH 10. Very fine powder with particle size of 50 nm was obtained at calcination temperature of $800^{\circ}C$ for 4 hours. LSCF cathode synthesized at pH 7 showed the highest electric conductivity in the temperature range of $600^{\circ}C$ to $900^{\circ}C$ its value was 950 S/cm at $900^{\circ}C$ Under same synthesis conditions, polarization resistance of each LSCF cathode was changed with different calcination temperatures. As-prepared powder presented 2.52, 1.54 and $2.58\;{\Omega}$ at $600^{\circ}C$ with ScSZ, 8Y-YSZ and GDC as its electrolyte respectively after calcination at $800^{\circ}C$ for 4 hours.

Modified oxalate method에 의해 합성한 중온형 Solid Oxide Fuel Cell 용 LSCF cathoded의 pH 변화에 따른 분말특성 및 여러 종류의 전해질에 따른 전극특성에 대해 연구하였다. LSCF를 합성하기 위한 출발물질로는 La, Sr, Co 및 Fe의 염화물과 oxalic acid, ethanol 및 $NH_4OH$를 사용하여, $80^{\circ}C$ 에서 pH 2, 6, 7, 8, 9 및 10에서 합성하였다. 합성한 LSCF 분말은 pH $2{\sim}9$까지는 단일상의 LSCF 결정상을 생성하였다. 그러나, PH 10에서는 LSCF결정상 외에 이차상인 $La_2O_3$ 결정상이 나타났으며, 또한 $800^{\circ}C$에서 4시간 하소한 경우 50 nm정도의 작은 크기를 나타내었다. 합성한 LSCF cathode 분말의 전기전도도는 pH 7에서 합성한 LSCF 분말의 경우 $600^{\circ}C$부터 $900^{\circ}C$까지 측정하였을 때 약 950 S/cm의 높은 값을 나타내었다. 또한 분극저항의 경우 같은 합성 조건에서 합성한 LSCF 분말이라도 하소조건에 따라 다른 결과를 나타내었는데, $800^{\circ}C$에서 하소한 분말의 경우 $1200^{\circ}C$에서 하소한 분말 보다 낮은 분극저항을 나타내었다. 특히 $800^{\circ}C$에서 4시간 하소하여 합성한 LSCF 분말은 $600^{\circ}C$에서 Scandia Stabilized Zirconia (ScSZ), yttria (8mol.%)-stabilized zirconia(8Y-YSZ) 및 Gadolinium Doped Ceria(GDC) 전해질을 사용하였을 때, 전극면적이 $0.5\;cm^2$일 때 각각 2.52, 1.54 및 $2.58\;{\Omega}$을 나타내었다.

Keywords

References

  1. H. B. Wang, J. F. Gao, D. K. Peng and G. Y. Meng, 'Plasma deposition of $La_{0.8}Sr_{0.2}MnO_3$ thin films on yttria-stabilized zirconia from aerosol precursor' Mater. Chem. and Phys., 72, 3, 297 (2001) https://doi.org/10.1016/S0254-0584(01)00331-5
  2. E. Bucher, W. Sitte, I. Rom, I. Papst, W. Grogger and F. Hofer, 'Microstructure and ionic conductivity of strontium-substituted lanthanum cobaltites', Solid state ionics, 152, 417 (2002) https://doi.org/10.1016/S0167-2738(02)00354-5
  3. V. V. Kharton, A. V. Kovalevsky, A. P. Viskup, F. M. Figueiredo, A. A. Yaremchenko, E. N. Naumovich and F. M. B. Marques, 'Oxygen permeability and Faradaic efficiency of $Ce_{0.8}Gd_{0.2}O_2-d-La_{0.7}Sr_{0.3}MnO_{3-\delta}$ composites', J. of the Euro. Ceram. Soc., 21, 1763 (2001) https://doi.org/10.1016/S0955-2219(01)00167-4
  4. Tsang-Tse Fang and Horng-Bin Lin, 'Factors Affecting the Preparation of Barium Titanyl Oxalate Terra- hydrate', J. Am. Ceram. Soc., 72, 10, 1988 (1989)
  5. H. Yamamura, A. Watanabe, S. Shirasaki, Y. Moriyoshi and M. Tanada, 'Preperation of Barium Titanat by Oxalate Method in Ethanol Solution', Ceramics International, 11, 1, 17 (1985) https://doi.org/10.1016/S0272-8842(85)90016-1
  6. Liana Marta, Ossi Horovitz and Maria Zaharescu, 'Analytical Study of Oxalates Coprecipitation', Leonardo J. Sci., 2, 72 (2003)
  7. E. Knaepen, M. K. Van Bael, I. Schildermans, R. Nouwen, J. D'Haen, M. D'Olieslaeger, C. Quaeyhaegens, D. Franco, J. Yperman, J.Mullens, L. C. Van Poucke, 'Thermochim. Acta', 318, 143 (2000) https://doi.org/10.1016/S0040-6031(98)00339-6
  8. G. Vanhoylan, R. Nouwen, M. K. Van Bael, J. Yperman, J. Mullens, L. C. Van Poucke, 'Thermochim. Acta', 354, 145 (2000) https://doi.org/10.1016/S0040-6031(00)00469-X
  9. Basma A. A. Balboul, A. M. El-Roudi, Ebthal Samir, A. G. Othman, 'Thermochim. Acta', 387, 109 (2002) https://doi.org/10.1016/S0040-6031(01)00834-6
  10. L. W. Tai, M. M. Nasrallah, H. U. Anderson, D. M. Sparlin, S.R. Sehlin, 'Structure and electrical properties of $La_{1-x}Sr_xCo_{1-y}Fe_yO_3$ . Part 1. The system $La_{0.8}Sr_{0.2}Co_{1-y}Fe_yO_3$', Solid State Ionics, 76, 259 (1995) https://doi.org/10.1016/0167-2738(94)00244-M
  11. L.W. Tai, M.M. Nasrallah, H.U. Anderson, D.M. Sparlin, S.R. Sehlin, 'Structure and electrical properties of $La_{1-x}Sr_xCo_{1-y}Fe_yO_3$ Part 2. The system $La_{1-x}Sr_xCo_{0.2}Fe_{0.8}O_3$' Solid State Ionics, 76, 273 (1995) https://doi.org/10.1016/0167-2738(94)00245-N