STRUCTURE, CONDUCTIVITY, AND CELL PERFORMANCE OF CODOPED CERIA BASED ELECTROLYTES Ce<sub>1-x-y</sub>Gd<sub>x</sub>Ln<sub>y</sub>O<sub>2-?</sub> (Ln=Dy, Er, atau Nd dan x,y=0,05 atau 0,1)
Solid Oxide Fuel Cell (SOFC), just like a battery, is an electrochemical device that convert chemical energy from fuel into electrical energy. Up to now, the development of SOFC is focusing on lowering the operating temperature to intermediate range (500-700 °C), called Intermediate Temperature SOFC...
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Kimia fisik Hardian, Arie STRUCTURE, CONDUCTIVITY, AND CELL PERFORMANCE OF CODOPED CERIA BASED ELECTROLYTES Ce<sub>1-x-y</sub>Gd<sub>x</sub>Ln<sub>y</sub>O<sub>2-?</sub> (Ln=Dy, Er, atau Nd dan x,y=0,05 atau 0,1) |
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Solid Oxide Fuel Cell (SOFC), just like a battery, is an electrochemical device that convert chemical energy from fuel into electrical energy. Up to now, the development of SOFC is focusing on lowering the operating temperature to intermediate range (500-700 °C), called Intermediate Temperature SOFC (IT-SOFC). Lowering the operating temperature give some benefit such as lowering the fabrication cost due to the probabilty of using cheaper interconnect material (metal based) and increase the durability of SOFC performance. However, lowering the temperature increase the electrolyte resistance which lead to the low cell performace. The challenge of IT-SOFC development is to find alternative electrolyte which has high conductivity at IT range.
Ceria (CeO2) based electrolytes become one of the best candidate for IT-SOFC electrolyte due to their higher ionic conductivity than a commercial electrolyte Yttria Stabilized Zirconia (YSZ) at IT range. The conductivity of ceria will be increase many times after it has been doped by lower valence cation (M3+ or M2+) such as Gd3+, Nd3+, Ca2+, etc. The researchs on ceria based electrolyte are focusing on finding an ideal dopant and its ideal composition in order to achieve higher conductivity which is higher than 10-2 S cm-1 and lower activation energy below 1 eV at 600 °C. Codoped and multidoped strategy have been also used in order to reach those targets.
The aims of this research was to find the effect of codoping composition, the effect of synthesis method on ionic conductivity. Gd3+ dopan had been choosen as the first dopant and Nd3+, Dy3+, or Er3+ dopants had been choosen as the second dopant. The composition of first and second dopants was 5%5%, 5%10%, 10%5%, and 10%10% (in mol%), respectively. These variation produced twelve types of codoped ceria. Abbreviation was used to facilitate the writing of sample compositions, for example GNDC510 means 5%Gadolinia 10%Neodimia Doped Ceria or Ce0.85Gd0.05Nd0.1O1.925.
Based on conductivity analysis using electrical impedance spectroscopy, all codoped ceria have conductivity value which is higher than 10-2 S cm-1 and the activation energy were below 1 eV at 600 °C. The best composition was GNDC510 which has 1.05x10-2 S cm-1 conductivity and 0.8 eV activation energy at 600 °C. GNDC sets have higher conductivity than GDDC and GEDC sets due to the crystallographic effective index (Ieff) of GNDC sets were closer to unity and the average of atomic number of dopants were closer to the atomic number of Pm (Promethium) which is 61. However, the assumption about critical radius seems could not explain the trend of the conductivity data.
The conductivity increase for material with 10% to 15% of total dopants concentration and then decrease at 20% of total dopants concentration. The decrease of conductity at higher total dopant concentration was due to the increasing of pair defect concentration ([?????????????-??????????]). An extra vibration Raman mode was found in both GDDC and GNDC set which is in the range of 540-600 cm-1. These vibration mode is believed related to the defect pair vibration mode. Its intensity was also increase by increasing the total dopant concentration. The Raman spectra of GEDC sets showed different profile probably due to the fluorescence effect of erbium dopant.
The relative density of GNDC510 increase as large as 23% with addition of 0.5% w/w CuO as sintering aid, even the sintering temperature was 15% lower then the previous solid state sample. There is no CuO pattern was detected in XRD pattern of CuO added GNDC510 which is probably due to the intensity of CuO pattern was too small or the CuO solved in GNDC510 structure. However, the conductivity of GNDC510+0.5% CuO was lower than GNDC510 especially at grain boundary conductivity. This probably due to the aggregation of CuO at grain boundary and become a resistive phase.
The used of citrate complexation method increase the relative density and the conductivity of GNDC510. The relative density of GNDC510 was 22% higher than the previous solid state sample even at 1350 °C of sintering temperature. The increasing of relative density was probably due to the smaller size of particle. The conductivity either grain or grain boundary of citrate sample were also increase due to the dopant distribution with higher homogenity and the smaller size of grain which is produced by this method.
The single cell of electrolyte supported SOFC has been successfully fabricated using screen printing technique. Platinum mesh has been used as the current collector, Ni-GDC15 has been used as the anode, and LSCF6428 has been used as the cathode. The OCV of the cell was 0.971 V and the maximum power density (MPD) was 30 mW cm-2 at 600 °C using humidified hydrogen fuel (97%/3%) and air as oxidant. The low of OCV due to the fuel crossover through the electrolyte pores. The low of MPD due to the high of area spesific resistance (ASR) of the cell which is 4.1 ???? cm2. |
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Dissertations |
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Hardian, Arie |
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Hardian, Arie |
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Hardian, Arie |
title |
STRUCTURE, CONDUCTIVITY, AND CELL PERFORMANCE OF CODOPED CERIA BASED ELECTROLYTES Ce<sub>1-x-y</sub>Gd<sub>x</sub>Ln<sub>y</sub>O<sub>2-?</sub> (Ln=Dy, Er, atau Nd dan x,y=0,05 atau 0,1) |
title_short |
STRUCTURE, CONDUCTIVITY, AND CELL PERFORMANCE OF CODOPED CERIA BASED ELECTROLYTES Ce<sub>1-x-y</sub>Gd<sub>x</sub>Ln<sub>y</sub>O<sub>2-?</sub> (Ln=Dy, Er, atau Nd dan x,y=0,05 atau 0,1) |
title_full |
STRUCTURE, CONDUCTIVITY, AND CELL PERFORMANCE OF CODOPED CERIA BASED ELECTROLYTES Ce<sub>1-x-y</sub>Gd<sub>x</sub>Ln<sub>y</sub>O<sub>2-?</sub> (Ln=Dy, Er, atau Nd dan x,y=0,05 atau 0,1) |
title_fullStr |
STRUCTURE, CONDUCTIVITY, AND CELL PERFORMANCE OF CODOPED CERIA BASED ELECTROLYTES Ce<sub>1-x-y</sub>Gd<sub>x</sub>Ln<sub>y</sub>O<sub>2-?</sub> (Ln=Dy, Er, atau Nd dan x,y=0,05 atau 0,1) |
title_full_unstemmed |
STRUCTURE, CONDUCTIVITY, AND CELL PERFORMANCE OF CODOPED CERIA BASED ELECTROLYTES Ce<sub>1-x-y</sub>Gd<sub>x</sub>Ln<sub>y</sub>O<sub>2-?</sub> (Ln=Dy, Er, atau Nd dan x,y=0,05 atau 0,1) |
title_sort |
structure, conductivity, and cell performance of codoped ceria based electrolytes ce<sub>1-x-y</sub>gd<sub>x</sub>ln<sub>y</sub>o<sub>2-?</sub> (ln=dy, er, atau nd dan x,y=0,05 atau 0,1) |
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https://digilib.itb.ac.id/gdl/view/32171 |
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id-itb.:321712018-12-04T09:56:13ZSTRUCTURE, CONDUCTIVITY, AND CELL PERFORMANCE OF CODOPED CERIA BASED ELECTROLYTES Ce<sub>1-x-y</sub>Gd<sub>x</sub>Ln<sub>y</sub>O<sub>2-?</sub> (Ln=Dy, Er, atau Nd dan x,y=0,05 atau 0,1) Hardian, Arie Kimia fisik Indonesia Dissertations Ceria, Codoped, Electrolyte, Intermediate Temperature, Single Cell, SOFC INSTITUT TEKNOLOGI BANDUNG https://digilib.itb.ac.id/gdl/view/32171 Solid Oxide Fuel Cell (SOFC), just like a battery, is an electrochemical device that convert chemical energy from fuel into electrical energy. Up to now, the development of SOFC is focusing on lowering the operating temperature to intermediate range (500-700 °C), called Intermediate Temperature SOFC (IT-SOFC). Lowering the operating temperature give some benefit such as lowering the fabrication cost due to the probabilty of using cheaper interconnect material (metal based) and increase the durability of SOFC performance. However, lowering the temperature increase the electrolyte resistance which lead to the low cell performace. The challenge of IT-SOFC development is to find alternative electrolyte which has high conductivity at IT range. Ceria (CeO2) based electrolytes become one of the best candidate for IT-SOFC electrolyte due to their higher ionic conductivity than a commercial electrolyte Yttria Stabilized Zirconia (YSZ) at IT range. The conductivity of ceria will be increase many times after it has been doped by lower valence cation (M3+ or M2+) such as Gd3+, Nd3+, Ca2+, etc. The researchs on ceria based electrolyte are focusing on finding an ideal dopant and its ideal composition in order to achieve higher conductivity which is higher than 10-2 S cm-1 and lower activation energy below 1 eV at 600 °C. Codoped and multidoped strategy have been also used in order to reach those targets. The aims of this research was to find the effect of codoping composition, the effect of synthesis method on ionic conductivity. Gd3+ dopan had been choosen as the first dopant and Nd3+, Dy3+, or Er3+ dopants had been choosen as the second dopant. The composition of first and second dopants was 5%5%, 5%10%, 10%5%, and 10%10% (in mol%), respectively. These variation produced twelve types of codoped ceria. Abbreviation was used to facilitate the writing of sample compositions, for example GNDC510 means 5%Gadolinia 10%Neodimia Doped Ceria or Ce0.85Gd0.05Nd0.1O1.925. Based on conductivity analysis using electrical impedance spectroscopy, all codoped ceria have conductivity value which is higher than 10-2 S cm-1 and the activation energy were below 1 eV at 600 °C. The best composition was GNDC510 which has 1.05x10-2 S cm-1 conductivity and 0.8 eV activation energy at 600 °C. GNDC sets have higher conductivity than GDDC and GEDC sets due to the crystallographic effective index (Ieff) of GNDC sets were closer to unity and the average of atomic number of dopants were closer to the atomic number of Pm (Promethium) which is 61. However, the assumption about critical radius seems could not explain the trend of the conductivity data. The conductivity increase for material with 10% to 15% of total dopants concentration and then decrease at 20% of total dopants concentration. The decrease of conductity at higher total dopant concentration was due to the increasing of pair defect concentration ([?????????????-??????????]). An extra vibration Raman mode was found in both GDDC and GNDC set which is in the range of 540-600 cm-1. These vibration mode is believed related to the defect pair vibration mode. Its intensity was also increase by increasing the total dopant concentration. The Raman spectra of GEDC sets showed different profile probably due to the fluorescence effect of erbium dopant. The relative density of GNDC510 increase as large as 23% with addition of 0.5% w/w CuO as sintering aid, even the sintering temperature was 15% lower then the previous solid state sample. There is no CuO pattern was detected in XRD pattern of CuO added GNDC510 which is probably due to the intensity of CuO pattern was too small or the CuO solved in GNDC510 structure. However, the conductivity of GNDC510+0.5% CuO was lower than GNDC510 especially at grain boundary conductivity. This probably due to the aggregation of CuO at grain boundary and become a resistive phase. The used of citrate complexation method increase the relative density and the conductivity of GNDC510. The relative density of GNDC510 was 22% higher than the previous solid state sample even at 1350 °C of sintering temperature. The increasing of relative density was probably due to the smaller size of particle. The conductivity either grain or grain boundary of citrate sample were also increase due to the dopant distribution with higher homogenity and the smaller size of grain which is produced by this method. The single cell of electrolyte supported SOFC has been successfully fabricated using screen printing technique. Platinum mesh has been used as the current collector, Ni-GDC15 has been used as the anode, and LSCF6428 has been used as the cathode. The OCV of the cell was 0.971 V and the maximum power density (MPD) was 30 mW cm-2 at 600 °C using humidified hydrogen fuel (97%/3%) and air as oxidant. The low of OCV due to the fuel crossover through the electrolyte pores. The low of MPD due to the high of area spesific resistance (ASR) of the cell which is 4.1 ???? cm2. text |