PREPARATION OF ZINC-DOPED LANTHANUM STRONTIUM GALLATE SOLID ELECTROLYTE USING A REACTION-SINTERING...
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PREPARATION OF ZINC-DOPED LANTHANUM STRONTIUM GALLATE SOLID ELECTROLYTE USING A REACTION-SINTERING PROCESS Yi-Cheng Liou*, Chung-Che Lan, Song-Ling Yang Yi-Cheng Liou*, Chung-Che Lan, Song-Ling Yang Department of Electronics Engineering, Kun Department of Electronics Engineering, Kun Shan University, Tainan Hsien 71003, Shan University, Tainan Hsien 71003, Taiwan, R.O.C. Taiwan, R.O.C. *Corresponding author. [email protected] *Corresponding author. [email protected] La La 0.8 0.8 Sr Sr 0.2 0.2 Ga Ga 0.8 0.8 Zn Zn 0.2 0.2 O O 2.8 2.8 (LSGZ) ceramics prepared using a reaction-sintering process was investigated (LSGZ) ceramics prepared using a reaction-sintering process was investigated in this study. Without any calcination involved, the mixture of raw materials was pressed and in this study. Without any calcination involved, the mixture of raw materials was pressed and sintered directly. SrLaGa sintered directly. SrLaGa 3 O O 7 is the major phase in 1150 is the major phase in 1150 C sintered pellets and decreased at higher C sintered pellets and decreased at higher sintering temperature 1250 sintering temperature 1250 C. La C. La 0.8 0.8 Sr Sr 0.2 0.2 Ga Ga 0.8 0.8 Zn Zn 0.2 0.2 O O 2.8 2.8 became the major phase in pellets sintered at became the major phase in pellets sintered at 1250 1250 o C/2 h. Density of La C/2 h. Density of La 0.8 0.8 Sr Sr 0.2 0.2 Ga Ga 0.8 0.8 Zn Zn 0.2 0.2 O O 2.8 2.8 ceramics increases with sintering temperature and ceramics increases with sintering temperature and reaches a maximum 6.71 g/cm reaches a maximum 6.71 g/cm 3 at 1230 at 1230 o C for 6 h. C for 6 h. The reaction-sintering process has proven a simple The reaction-sintering process has proven a simple and effective method in preparing and effective method in preparing La La 0.8 0.8 Sr Sr 0.2 0.2 Ga Ga 0.8 0.8 Zn Zn 0.2 0.2 O O 2.8 2.8 ceramics for solid electrolyte applications ceramics for solid electrolyte applications in solid oxide fuel cells. in solid oxide fuel cells. The XRD patterns of LSGZ sintered at 1150 o C and 1250C for 2 h are shown in Fig. 1. It can be seen reflections of SrLaGa 3 O 7 , LSGZ, SrLaGaO 4 and La 4 Ga 2 O 9 were detected. SrLaGa 3 O 7 is the major phase in 1150C sintered pellets and decreased at higher sintering temperature 1250C. LSGZ became the major phase in pellets sintered at 1250 o C/2 h. Therefore, reaction-sintering process can efficiently transform the mixture of raw materials into LSGZ phase. La 4 Ga 2 O 9 phase decreased obviously at 1250 o C. Using a Pechini-type process, Tas et al. reported that SrLaGaO 4 and SrLaGa 3 O 7 phases appeared in the calcined La 0.9 Sr 0.1 GaO 2.95 at 1200 o C and disappeared at 1340 o C/6 h calcination. SrLaGa 3 O 7 phase appeared after 6 h calcined at 700 o C and about 4-5 wt% of a mixture of the undesired SrLaGaO 4 and SrLaGa 3 O 7 phases still remained even after calcined at 1400 o C for 6 h. They also found SrLaGa 3 O 7 as a major phase in LSGZ calcined at 1000 o C via aqueous chemical precipitation and almost pure LSGZ at 1200 o C. SEM photographs of as-fired LSGZ ceramics sintered at 1150-1250 o C/2 h are shown in Fig. 2. Porous pellet with fine grains of about 2 μm formed at 1150 o C and 1170 o C. This means 1150-1170 o C sintering is not high enough for grain growth and densification in LSGZ ceramics prepared using the reaction-sintering process. It can be easily observed that pores decreased at 1200oC and grain size increased at temperatures 1200-1250 o C. The amount of pores decreased in LSGZ ceramics sintered for 4 h as shown in Fig. 3. Dense LSGZ could be obtained at sintering temperatures above 1230 o C. Dense structure is needed in electrolyte of SOFC to avoid mixing and reaction between fuel and oxygen gas. Tas et al. reported LSGZ powders consisted of round particles with an average diameter of 0.25 μm after calcined at 1000 o C for 6 h. The non-compacted LSGZ powder body consisted of dense 20 to 30 μm chunks was observed at 1300 o C 6 h calcination. Fig. 4 shows the shrinkage percentage of LSGZ ceramics sintered at various temperatures for 2-6 h. It increases from about 19-22% at 1150 o C to 24-25% at 1250 o C. In our study of La 0.8 Sr 0.2 Ga 0.83 Mg 0.17 O 2.815 ceramics via reaction– sintering process, shrinkage of 17-20% at 1300oC and 26-28% at 1400 o C were found. It implies a lower temperature is needed in Zn-doped than in Mg-doped LaSrGaO 3-δ ceramics prepared via reaction-sintering process. In Fig. 5, density of LSGZ ceramics increases with sintering temperature and reaches a maximum 6.71 g/cm 3 at 1230 o C for 6 h. Fig. 3 SEM photographs of as- fired LSGZ ceramics sintered at (A) 1150 o C, (B) 1170 o C, (C) 1200 o C, (D) 1230 o C, and (E) 1250 o C for 4 h. Fig. 5 Density of LSGZ ceramics sintered at various temperatures for 2-6 h. Fig. 4 Shrinkage percentage of LSGZ ceramics sintered at various temperatures for 2-6 h. Fig. 1 XRD patterns of LSGZ sintered at (A) 1150 o C and (B) 1250 o C for 2 h. (1: LaGaO 3 ICDD PDF # 00-054-0870; 2: SrLaGaO 4 ICDD PDF # 01- 080-1806; 3:SrLaGa 3 O 7 ICDD PDF # 00-045-0637; 4: La4Ga 2 O 9 ICDD PDF # 00-037-1433) Fig. 2 SEM photographs of as- fired LSGZ ceramics sintered at (A) 1150 o C, (B) 1170 o C, (C) 1200 o C, (D) 1230 o C, and (E) 1250 o C for 2 h. Materials and Austceram 2007 Materials and Austceram 2007 July 4 - 6, 2007, Sydney , Australia July 4 - 6, 2007, Sydney , Australia
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Transcript of PREPARATION OF ZINC-DOPED LANTHANUM STRONTIUM GALLATE SOLID ELECTROLYTE USING A REACTION-SINTERING...
PREPARATION OF ZINC-DOPED LANTHANUM STRONTIUM GALLATE SOLID ELECTROLYTE USING A REACTION-SINTERING PROCESS
Yi-Cheng Liou*, Chung-Che Lan, Song-Ling YangYi-Cheng Liou*, Chung-Che Lan, Song-Ling YangDepartment of Electronics Engineering, KunDepartment of Electronics Engineering, Kun Shan University, Tainan Hsien 71003, Taiwan, R.O.C.Shan University, Tainan Hsien 71003, Taiwan, R.O.C.
*Corresponding author. [email protected]*Corresponding author. [email protected]
LaLa0.80.8SrSr0.20.2GaGa0.80.8ZnZn0.20.2OO2.82.8 (LSGZ) ceramics prepared using a reaction-sintering process was investigated in this study. Without any calcination (LSGZ) ceramics prepared using a reaction-sintering process was investigated in this study. Without any calcination
involved, the mixture of raw materials was pressed and sintered directly. SrLaGainvolved, the mixture of raw materials was pressed and sintered directly. SrLaGa33OO77 is the major phase in 1150 is the major phase in 1150C sintered pellets and decreased C sintered pellets and decreased
at higher sintering temperature 1250at higher sintering temperature 1250C. LaC. La0.80.8SrSr0.20.2GaGa0.80.8ZnZn0.20.2OO2.82.8 became the major phase in pellets sintered at 1250 became the major phase in pellets sintered at 1250ooC/2 h. Density of C/2 h. Density of
LaLa0.80.8SrSr0.20.2GaGa0.80.8ZnZn0.20.2OO2.82.8 ceramics increases with sintering temperature and reaches a maximum 6.71 g/cm ceramics increases with sintering temperature and reaches a maximum 6.71 g/cm33 at 1230 at 1230ooC for 6 h. C for 6 h. The reaction-sintering The reaction-sintering
process has proven a simple and effective method in preparing process has proven a simple and effective method in preparing LaLa0.80.8SrSr0.20.2GaGa0.80.8ZnZn0.20.2OO2.82.8 ceramics for solid electrolyte applications in solid oxide fuel ceramics for solid electrolyte applications in solid oxide fuel
cells. cells. The XRD patterns of LSGZ sintered at 1150oC and 1250C for 2 h are shown in Fig. 1. It can be seen reflections of SrLaGa3O7, LSGZ, SrLaGaO4 and La4Ga2O9 were detected. SrLaGa3O7 is the major phase in 1150C sintered pellets and decreased at higher sintering temperature 1250C. LSGZ became the major phase in pellets sintered at 1250oC/2 h. Therefore, reaction-sintering process can efficiently transform the mixture of raw materials into LSGZ phase. La4Ga2O9 phase decreased obviously at 1250oC. Using a Pechini-type process, Tas et al. reported that SrLaGaO4 and SrLaGa3O7 phases appeared in the calcined La0.9Sr0.1GaO2.95 at 1200oC and disappeared at 1340oC/6 h calcination. SrLaGa3O7 phase appeared after 6 h calcined at 700oC and about 4-5 wt% of a mixture of the undesired SrLaGaO4 and SrLaGa3O7 phases still remained even after calcined at 1400oC for 6 h. They also found SrLaGa3O7 as a major phase in LSGZ calcined at 1000oC via aqueous chemical precipitation and almost pure LSGZ at 1200oC.
SEM photographs of as-fired LSGZ ceramics sintered at 1150-1250oC/2 h are shown in Fig. 2. Porous pellet with fine grains of about 2 μm formed at 1150oC and 1170oC. This means 1150-1170oC sintering is not high enough for grain growth and densification in LSGZ ceramics prepared using the reaction-sintering process. It can be easily observed that pores decreased at 1200oC and grain size increased at temperatures 1200-1250oC. The amount of pores decreased in LSGZ ceramics sintered for 4 h as shown in Fig. 3. Dense LSGZ could be obtained at sintering temperatures above 1230oC. Dense structure is needed in electrolyte of SOFC to avoid mixing and reaction between fuel and oxygen gas. Tas et al. reported LSGZ powders consisted of round particles with an average diameter of 0.25 μm after calcined at 1000oC for 6 h. The non-compacted LSGZ powder body consisted of dense 20 to 30 μm chunks was observed at 1300oC 6 h calcination.
Fig. 4 shows the shrinkage percentage of LSGZ ceramics sintered at various temperatures for 2-6 h. It increases from about 19-22% at 1150oC to 24-25% at 1250oC. In our study of La0.8Sr0.2Ga0.83Mg0.17O2.815 ceramics via reaction–sintering process, shrinkage of 17-20% at 1300oC and 26-28% at 1400oC were found. It implies a lower temperature is needed in Zn-doped than in Mg-doped LaSrGaO3-δ ceramics prepared via reaction-sintering process. In Fig. 5, density of LSGZ ceramics increases with sintering temperature and reaches a maximum 6.71 g/cm3 at 1230oC for 6 h.
Fig. 3 SEM photographs of as-fired LSGZ ceramics sintered at (A) 1150oC, (B) 1170oC, (C) 1200oC, (D) 1230oC, and (E) 1250oC for 4 h.
Fig. 5 Density of LSGZ ceramics sintered at various temperatures for 2-6 h.
Fig. 4 Shrinkage percentage of LSGZ ceramics sintered at various temperatures for 2-6 h.
Fig. 1 XRD patterns of LSGZ sintered at (A) 1150oC and (B) 1250oC for 2 h. (1: LaGaO3 ICDD PDF # 00-054-0870; 2: SrLaGaO4 ICDD PDF # 01- 080-1806; 3:SrLaGa3O7 ICDD PDF # 00-045-0637; 4: La4Ga2O9 ICDD PDF # 00-037-1433)
Fig. 2 SEM photographs of as-fired LSGZ ceramics sintered at (A) 1150oC, (B) 1170oC, (C) 1200oC, (D) 1230oC, and (E) 1250oC for 2 h.
Materials and Austceram 2007Materials and Austceram 2007July 4 - 6, 2007, Sydney , AustraliaJuly 4 - 6, 2007, Sydney , Australia
