Sains Malaysiana 41(1)(2012): 95–102

Pencirian Fizikal dan Terma Komposit Seramik Elektrolit SDC-(Li/Na)₂CO₃

(Physical and Thermal Characterisations of SDC-(Li/Na)₂CO₃ Electrolyte Ceramic Composites)

Jarot Raharjo, Andanastuti Muchtar*, Wan Ramli Wan Daud, Norhamidi Muhamad

& Edy Herianto Majlan

Institut Sel Fuel, Universiti Kebangsaan Malaysia, 43600UKM Bangi,

Selangor D.E. Malaysia

Jarot Raharjo

Pusat Teknologi Material, Badan Pengkajian dan Penerapan Teknologi

Jl. MH. Thamrin no. 8, Jakarta Pusat, 10340, Indonesia

Received: 10 May 2010 / Accepted:  22 December 2010

ABSTRACT

This paper presents the physical and thermal properties of composite electrolytes based on samarium-doped cerium (Ce0.8Sm0.2O1.9, SDC) and carbonates (67 mol% Li2CO3/ 33mol% Na2CO3). SDC–(Li/Na)2CO3 composite is an excellent ionic conductor that is potentially viable for use as an electrolyte material for low temperature solid oxide fuel cells (LT-SOFC). Characterisation of the composite electrolyte includes the morphology, surface area, thermal analysis and porosity of the electrolyte pellets. The fabrication of the SDC–(Li/Na)2CO3 electrolyte composites were achieved in two steps: (1) preparation of the samarium-doped cerium powders by sol-gel and (2) mixing of the samarium-doped cerium with carbonates in various compositions by solid state reaction. The electrolyte pellets were compacted at different pressures (25, 50, 150 and 200 MPa) and sintered at 500, 600, 700 and 800oC. The XRD results demonstrated that the introduction of carbonates did not change the SDC phase structure. FESEM images showed that the carbonate component was amorphous and well distributed in the SDC matrix. The greater the carbonate content in the composite, the smaller the surface area. Thermal analysis indicated that the melting point of the carbonate phase decreased with a reduction of the fraction of carbonate content. The optimum porosity most suitable for LT-SOFC electrolytes, 3.38% and 4.85%, were achieved for samples with carbonate content of 20% (SDC8020) and 30% (SDC7030), respectively. These were for samples sintered at 600oC and cold pressed at 200 MPa.

Keywords: Electrolyte composites; physical and thermal characterisations; pressureless sintering; SDC-(Li/Na)2CO3; solid oxide fuel cells

ABSTRAK

Dalam kertas ini dibentangkan hasil kajian sifat fizikal dan terma komposit elektrolit berasaskan samarium terdop seria (Ce0.8Sm0.2O1.9, SDC) dan karbonat (67%mol Li2CO3/ 33%mol Na2CO3). Komposit SDC-(Li/Na)2CO3 adalah pengalir berion yang berpotensi digunakan sebagai bahan elektrolit sel fuel oksida pepejal bersuhu rendah (LT-SOFC). Pencirian komposit elektrolit ini meliputi morfologi, luas permukaan bahan, analisis terma dan keliangan pelet elektrolit. Komposit elektrolit SDC-(Li/Na)2CO3 disediakan dalam dua langkah: (1) penyediaan serbuk samarium terdop seria melalui kaedah sol-gel dan (2) pencampuran samarium terdop seria dan karbonat dalam pelbagai komposisi yang berbeza melalui kaedah tindak balas keadaan pepejal. Pelet elektrolit dihasilkan dengan tekanan mampatan 25, 50, 150 and 200 MPa pada suhu pensinteran 500, 600, 700 dan 800oC. Keputusan XRD menunjukkan bahawa penambahan karbonat tidak mengubah struktur fasa SDC. Keputusan FESEM menunjukkan bahawa sebatian karbonat adalah amorfus dan tersebar dengan baik dalam matriks SDC. Semakin tinggi kandungan karbonat dalam komposit, luas permukaan serbuk komposit didapati semakin kecil. Keputusan analisis terma menunjukkan bahawa takat lebur fasa karbonat berkurang dengan berkurangnya kandungan karbonat. Keliangan optimum yang sesuai bagi elektrolit LT-SOFC iaitu 3.38% dan 4.85% telah dicapai masing-masing untuk sampel dengan kandungan karbonat 20% (SDC8020) dan 30% (SDC7030) dengan suhu pensinteran 600oC dan tekanan mampatan 200 MPa.

Kata kunci: Komposit elektrolit; SDC-(Li/Na)2CO3; pencirian fizikal dan terma; pensinteran tanpa tekanan; sel fuel oksida pepejal

REFERENCES

Boden, A., Di, J., Lagergren, C., Lindbergh, G. & Wang., C.Y. 2007. Conductivity of SDC and (Li/Na)2CO3 composite electrolytes in reducing and oxidising atmospheres. Journal of Power Sources 172: 520-529.

Center for Research in Computational Thermochemistry. 2009. Compound and solution data bases (atas talian). http://www.crct.polymtl.ca/fact/Documentation/FTsalt [28 April 2009].

Huang, J., Gao, Z. & Mao, Z. 2010. Effect of salt composition on the electrical properties of samaria-doped seria/ carbonate composite electrolytes for low-temperature SOFCs. International Journal of Hydrogen Energy 35: 4270-4275.

Huang, J., Zongqiang, M., Zhixiang, L. & Cheng, W. 2008. Performance of fuel cells with proton-conducting ceria-based composite electrolyte and nickel-based electrodes. Journal of Power Sources 175: 238-243.

Li, H., Xia, C., Zhu, M., Zhou, Z. & Meng, G. 2006. Reactive Ce0.8Sm0.2O1.9 powder synthesized by carbonate coprecipitation : Sintering and electrical characteristics. Acta Materialia 54: 721-727.

Li, S., Wang, X. & Zhu, B. 2007. Novel ceramic fuel cell using non-ceria-based composites as electrolyte. Electrochemistry Communications 9 (12): 2863-2866.

Ma, Y., Wang, X., Raza, R., Muhammed, M. & Zhu, B. 2010. Thermal stability study of SDC/Na2CO3 nanocomposite electrolyte for low-temperature SOFCs. International Journal of Hydrogen Energy 35: 2580-2585

Raza, R., Wang, X., Mac, Y., Liua, X. & Zhu, B. 2010. Improved ceria–carbonate composite electrolytes. International Journal of Hydrogen Energy 35: 2684-2688.

Steele, B.C.H. 2001. Material science and engineering: the enabling technology for the commercialisation of fuel cell systems. Journal of Material 36: 1053-1068.

Wang, X., Ma, Y., Raza, R., Muhammed, M. & Zhu, B. 2008. Novel core-shell SDC/amorphous Na2CO3 nanocomposite electrolyte for low-temperature SOFCs. Electrochemistry Communications 10(10): 1617-1620.

Xia, C., Li, Y. Tian, Y., Liu, Q., Wang, Z., Jia, L., Zhao, Y. & Li, Y. 2010. Intermediate temperature fuel cell with a doped ceria–carbonate composite electrolyte. Journal of Power Sources 195: 3149-3154.

Yokokawa, H., Tu, H., Iwanschitz, B. & Mai, Andreas. 2008. Fundamental mechanisms limiting solid oxide fuel cell durability. Journal of Power Sources 182: 400-412.

Zhu, B. 2006. Next generation fuel cell R&D. International Journal of Energy Research 30: 895-903.

Zhu, B., Liu X., Sun, M., Ji, S. & Sun, J. 2003. Calcium doped ceria-based materials for cost-effective intermediate temperature solid oxide fuel cells. Solid State Sciences 5: 1127-1134.

Zhu, B., Albinsson, I., Andersson, C., Borsand, K., Nilsson, M. & Mellander, B.E. 2006. Electrolysis studies based on ceria-based composites. Journal Electrochemistry Communications 8: 495-498.

Zhu, B., Li, S. & Mellander, B.-E. 2008. Theoretical approach on ceria-based two-phase electrolytes for low temperature (300-600oC) solid oxide fuel cells. Electrochemistry Communications 10: 302-305.

Zhu, B. & Mat, M.D. 2006. Studies on Dual Phase Ceria-based Composites in Electrochemistry. International Journal of Electrochemical Science 1: 383-402.

*Corresponding author; email: muchtar@vlsi.eng.ukm.my