1. 電子陶瓷研究室 Materials and Austceram 2007 July 4 - 6, 2007, Sydney, Australia. La 0.9 Sr 0.1 Ga 0.57 Mn 0.43 O 3 ANODE CERAMICS OF SOLID OXIDE FUEL CELLS PRODUCED USING REACTION-SINTERING PROCESS Yi-Cheng Liou*, Pei-Hung Yeh, Ming-Jih Lin Yi-Cheng Liou*, Pei-Hung Yeh, Ming-Jih Lin Department of Electronics Engineering, Kun Shan University, Tainan Hsien 71003, Taiwan, R.O.C. *Corresponding author. ycliou@mail.ksu.edu.tw La 0.9 Sr 0.1 Ga 0.57 Mn 0.43 O 3 (LSGM) anode ceramics of solid oxide fuel cells produced using a reaction-sintering process were investigated. Without any calcination involved, the mixture of La 2 O 3, SrCO 3, Ga 2 O 3 and MnO 2 was pressed and sintered directly. Porous LSGM ceramics could be obtained at 1230-1270 o C for 2 and 4 hours sintering. Temperatures higher than 1270 o C are too high to obtain useful porous LSGM ceramics for 6 h soak time. A lower sintering temperature is needed in preparing LSGM ceramics using a reaction-sintering process than using the conventional solid oxide method. Reaction-sintering process has proven a simple and effective method in preparing LSGM ceramics for applications in solid oxide fuel cell anode. The XRD patterns of LSGM ceramics are shown in figure 1. All the diffraction peaks match with peaks of ICDD PDF # 01-070-8683 (La0.73Sr0.27Ga0.1Mn0.9O3) and no second phases were found. Therefore, the reaction-sintering process is proven effective in preparing LSGM ceramics. This simple process is effective not only in preparing BaTi 4 O 9, Ba 5 Nb 4 O 15, Sr 5 Nb 4 O 15, CaNb 2 O 6, NiNb 2 O 6 and Pb-based complex perovskite ceramics but also effective in preparing LSGM ceramics. In Fig. 2, the SEM photographs of LSGM ceramics sintered at 1230 o C to 1300 o C for 2 h are shown. Porous pellets with fine grains were formed at 1230-1270oC/2 h sintering. Grains >10μm can be easily found in 1300oC/2 h sintering pellets. Pores are needed in anodes of SOFCs for the transformation of fuel gas. The SEM photographs of LSGM ceramics sintered at 1230 o C to 1300 o C for 4 h are illustrated in figure 3. Porous pellets with fine grains were still found at 1230-1250 o C sintering. Grain growth increased clearly in pellets sintered at 1270oC. In our investigation of La 0.8 Sr 0.2 Ga 0.83 Mg 0.17 O 2.815, grains of size less than 4μm were formed in pellets sintered at 1300 o C for 2-6 h. This indicates larger grains formed in Mn substituted than in Mg substituted LaSrGaO 3 ceramics. Figure 4 shows the SEM photographs of LSGM ceramics sintered at 1230 o C to 1300 o C for 6 h. Porous pellets with fine grains were found again at 1230-1250 o C/6 h sintering. Grains larger than 10μm can be easily found in 1270 o C and 1300 o C sintering pellets. Anodes of SOFCs must be porous to allow gas transport to the reaction sites. Amount of pores could be easily controlled by adjusting the sintering temperature or soak time in LSGM ceramics prepared using reaction-sintering process. This method is proven a simple and effective method to obtain useful LSGM anode material for SOFC. The shrinkage percentage of LSGM ceramics sintered at different temperatures and soak times are shown in Fig. 5. It increased from 10-14% at 1230 o C to 20-25% at 1300 o C and reached a maximum value 24.12% at 1300 o C/6 h. The density of LSGM ceramics increased with the sintering temperature and reached a maximum value 6.4 g/cm3 at 1300 o C/6 h as shown in Fig. 6. From the discussion above, porous LSGM ceramics could be obtained at 1230-1270 o C for 2 and 4 hours sintering. Temperatures higher than 1270 o C are too high to obtain useful porous LSGM ceramics for 6 h soak time. In LSGM prepared via conventional solid oxide method, Hsu et al. found the open porosity of LSGM dropped sharply from 30 to 5% at 1350°C/4 h sintering.13 It implies a lower sintering temperature is needed in preparing LSGM ceramics using a reaction-sintering process. Fig. 1 XRD patterns of LSGM ceramics sintered at 1230 o C and 1250 o C for 2 h. (Standard pattern of La 0.73 Sr 0.27 Ga 0.1 Mn 0.9 O 3 : ICDD PDF # 01-070- 8683 is used for comparison.) Fig. 2 SEM photographs of LSGM ceramics sintered at (A) 1230 o C, (B) 1250 o C, (C) 1270 o C, and (D) 1300 o C for 2 h. Fig. 3 SEM photographs of LSGM ceramics sintered at (A) 1230 o C, (B) 1250 o C, (C) 1270 o C, and (D) 1300 o C for 4 h. Fig. 4 SEM photographs of LSGM ceramics sintered at (A) 1230 o C, (B) 1250 o C, (C) 1270 o C, and (D) 1300 o C for 6 h. Fig. 5 Shrinkage of LSGM ceramics sintered at various temperatures and soak times. Fig. 6 Density of LSGM ceramics sintered at various temperatures and soak times.