Yi-Cheng Liou * , Yuh-Lin Huang

1. Materials and Austceram 2007 July 4 - 6, 2007, Sydney , Australia La0.8Sr0.2FeO3 CATHODE CERAMICS OF SOLID OXIDE FUEL CELLS PREPARED USING REACTION-SINTERING PROCESS Yi-Cheng Liou*, Yuh-Lin Huang Department of Electronics Engineering, KunShan University, Tainan Hsien 71003, Taiwan, R.O.C. *Corresponding author. ycliou@mail.ksu.edu.tw La0.8Sr0.2FeO3 (LSFO) cathode ceramics of solid oxide fuel cells prepared using a reaction-sintering process were investigated. Without any calcination involved, the mixture of La2O3, SrCO3, and Fe2O3 was pressed and sintered directly. LSFO ceramics were obtained after 2-6 h sintering at 1200-1270oC. Density increased with sintering temperature and reaches a maximum value 6.13 g/cm3 at 1270oC/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 La0.8Sr0.2FeO3 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 # 00-035-1480 standard pattern of La0.8Sr0.2FeO3. 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 BaTi4O9, Ba5Nb4O15, Sr5Nb4O15, CaNb2O6, ZnNb2O6 and Pb-based complex perovskite ceramics but also effective in preparing LSFO ceramics. Shrinkage percentage of LSFO increased from 8-13% at 1200oC to 16-23% at 1270oC 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/cm3 at 1270oC/6 h sintering. Hung et al. reported La0.8Sr0.2FeO3-δ with a density 5.931 g/cm3 (95.5% of theoretical value 6.211 g/cm3) after 1000oC/2 h calcination and 1320oC/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 usingreaction-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 1230oC and 1250oC 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 asLa content in LaxSr1-xFeO3 increased. Grains of 6.95 μm for x=0.2 and 3.37 μm for x=0.4 were observed in LaxSr1-xFeO3 sintered at 1250oC/4 h via the reaction-sintering process. It is expected that grains in La0.8Sr0.2FeO3 is smaller than grains in La0.4Sr0.6FeO3. Fig. 3 Density of LSFO ceramics sintered at varioustemperatures and soak time. Fig. 2 Shrinkage percentage of LSFO ceramics sintered atvarious temperatures and soak time. Fig. 4 SEM photographs of as-fired LSFO ceramics sintered for 2 h at 1230oC (A) and 1250oC(B);4 h at 1230oC (C) and 1250oC(D);6 h at 1230oC (E) and 1250oC(F). Fig. 1 XRD patterns of LSFO ceramics sintered at 1200oC and1230oC for 2 h. (La0.8Sr0.2FeO3: ICDD PDF # 00-035-1480)