La 0.8 Sr 0.2 FeO 3 CATHODE CERAMICS OF SOLID OXIDE FUEL CELLS PREPARED USING REACTION-SINTERING PROCESS Yi-Cheng Liou*, Yuh-Lin Huang Department of Electronics Engineering, Kun Shan University, Tainan Hsien 71003, Taiwan, R.O.C. *Corresponding author. La 0.8 Sr 0.2 FeO 3 (LSFO) cathode ceramics of solid oxide fuel cells prepared using a reaction-sintering process were investigated. Without any calcination involved, the mixture of La 2 O 3, SrCO 3, and Fe 2 O 3 was pressed and sintered directly. LSFO ceramics were obtained after 2-6 h sintering at o C. Density increased with sintering temperature and reaches a maximum value 6.13 g/cm 3 at 1270 o C/6 h. Porous pellets with fine grains about 1 μm were formed in LSFO ceramics. Pores decreased as sintering temperature and soak time increased. Reaction-sintering process has proven a simple and effective method in preparing La 0.8 Sr 0.2 FeO3 ceramics for applications in solid oxide fuel cell cathode. Fig. 1 shows XRD profiles of LSFO ceramics prepared using the reaction-sintering process. All peaks match well with the ICDD PDF # standard pattern of La 0.8 Sr 0.2 FeO 3. LSFO ceramics could be obtained successfully via a simple process even with the calcining stage bypassed. Therefore, the reaction-sintering process is proven effective in preparing LSFO 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, ZnNb 2 O 6 and Pb-based complex perovskite ceramics but also effective in preparing LSFO ceramics. Shrinkage percentage of LSFO increased from 8-13% at 1200 o C to 16-23% at 1270 o C as shown in Fig. 2. The density values of LSFO sintered at various temperatures are shown in Fig. 3. It increases with sintering temperature at a same trend as shrinkage value and reaches a maximum value 6.13 g/cm 3 at 1270 o C/6 h sintering. Hung et al. reported La 0.8 Sr 0.2 FeO 3-δ with a density g/cm 3 (95.5% of theoretical value g/cm 3 ) after 1000 o C/2 h calcination and 1320 o C/2 h sintering. Porous cathode is needed in SOFC to allow gas transport to the reaction sites. Amount of pores could be easily controlled by adjusting the sintering temperature or soak time in LSFO ceramics prepared using reaction-sintering process. This method is proven a simple and effective method to obtain useful LSFO cathode material for SOFC. SEM photographs of as-fired LSFO ceramics sintered at 1230 o C and 1250 o C for 2-6 h are shown in Fig. 4. Porous pellets with fine grains about 1 μm were formed in these LSFO ceramics. It can be easily observed that pores decreased as sintering temperature and soak time increased. In our previous study, grain size decreased as La content in La x Sr 1-x FeO 3 increased. Grains of 6.95 μm for x=0.2 and 3.37 μm for x=0.4 were observed in La x Sr 1-x FeO 3 sintered at 1250 o C/4 h via the reaction-sintering process. It is expected that grains in La 0.8 Sr 0.2 FeO 3 is smaller than grains in La 0.4 Sr 0.6 FeO 3. Fig. 1 XRD patterns of LSFO ceramics sintered at 1200 o C and 1230 o C for 2 h. (La 0.8 Sr 0.2 FeO 3 : ICDD PDF # ) Fig. 4 SEM photographs of as-fired LSFO ceramics sintered for 2 h at 1230 o C (A) and 1250 o C (B); 4 h at 1230 o C (C) and 1250 o C (D); 6 h at 1230 o C (E) and 1250 o C (F). Fig. 2 Shrinkage percentage of LSFO ceramics sintered at various temperatures and soak time. Fig. 3 Density of LSFO ceramics sintered at various temperatures and soak time. Materials and Austceram 2007 July 4 - 6, 2007, Sydney, Australia