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93 pooja
93 pooja
93 pooja
93 pooja
93 pooja
93 pooja
93 pooja
93 pooja
93 pooja
93 pooja
93 pooja
93 pooja
93 pooja
93 pooja
93 pooja
93 pooja
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  • 1. Paper ID : 93 Electrical conductivity of Ba-Sr-Co-Fe cathode material for SOFC Pooja Sawant, A N Shirsat, S Varma, B N Wani, S R Bharadwaj 11/12/2013 1
  • 2. overview …  Renewable Energy and Fuel Cells  Solid Oxide Fuel Cells  Cathode for SOFC  Synthesis  Characterization  Electrical Conductivity  Conclusions  Future Work  Acknowledgement 11/12/2013 2
  • 3. Renewables in energy production … Introduction to Fuel Cells … • • • • 11/12/2013 Based on hydrogen technology High efficiency, Low pollutant Sustainable fuel resources Energy-environment issues 3
  • 4.     Leading technology for future power generation Direct conversion of chemical energy into electrical energy Cleaner & Low Environmental Impact Fuels used are Renewable viz. landfill gas, Biomass based fuel, Hydrogen State-of-the-art SOFC Materials Configuration of components in a fuel cell car 11/12/2013 Electrolyte : Electrolyte is for oxygen ion conduction e.g. stabilizes zirconia Zr1-xYxO2x/2 (YSZ) Anode : Hydrogen oxidation happens at anode e.g. Ni-YSZ Cathode : Cathode works for the reduction of O2. e.g. La1-xSrxMnO3 (LSM) 4
  • 5. Requirements for Cathode material… Electron conducting Good porosity Good electrode kinetics Mechanical & chemical compatibility with electrolyte Ba0.5Sr0.5Co1-xFexO3−δ (BSCF) perovskite oxide was first reported as a potential IT-SOFC cathode material in 2004 System Studied… Ba0.5Sr0.5Co1−xFexO3−δ (BSCF) Compositions with respective labels Compound Ba0.5Sr0.5Co0.8Fe0.2O3-δ BSC8F2 Ba0.5Sr0.5Co0.6Fe0.4O3-δ BSC6F4 Ba0.5Sr0.5Co0.4Fe0.6O3-δ BSC4F6 Ba0.5Sr0.5Co0.2Fe0.8O3-δ 11/12/2013 Label BSC2F8 5
  • 6. Gel-combustion (GC) 11/12/2013 6
  • 7. Cation Complexation (CC) Effective ionic radius (IR) for Co and Fe ions with different oxidation states IR (Å) IR (Å) Co4+ Fe4+ 0.58 Co3+ 11/12/2013 0.53 0.61 Fe3+ 0.64 Co2+ 0.74 Fe2+ 0.78 7
  • 8. Cell Parameters and relative density of BSCF compositions Synthesized by gel combustion route Label System Lattice Parameters [Å] a Cell Vol. [Å3] Crystallite size (nm) 63.193 (37) Relative Density (%) 88 BSC8F2 Cubic 3.983 (1) BSC6F4 Cubic 3.972 (1) 62.675 (29) 78 52 BSC4F6 Cubic 3.962 (1) 62.195 (11) 81 129 BSC2F8 Cubic 3.949 (1) 61.584 (16) 79 49 100 Synthesized by Cation complexation route Label Lattice Parameters [Å] a Cell Vol. [Å3] BSC8F2 Cubic 3.981 (1) BSC6F4 Cubic BSC4F6 BSC2F8 11/12/2013 System Crystallite size (nm) 63.110 (24) Relative Density (%) 85 3.973 (0) 62.717 (11) 81 147 Cubic 3.965 (0) 62.340 (20) 82 150 Cubic 3.953 (1) 61.795 (30) 80 152 140 8
  • 9. Voltmeter V h l w A Current Source Ammeter Electric conductivity measurement by four – probe method. Constant current (I) is supplied, voltage across the two points (separated by l ) with change in temperature measured.  Resistance R= V/I Conductivity σ = l / R × w ×h 11/12/2013 9
  • 10. CC GC Specific Conductivity σ, Scm-1 (at 723 K) GC BSC8F2 20.27 38.86 BSC6F4 18.73 33.04 BSC4F6 11/12/2013 CC 37.95 32.82 BSC2F8 25.64 31.91 10
  • 11. Activation energy (eV) (400-700 K) GC BSC8F2 0.37 0.42 BSC6F4 0.33 0.39 BSC4F6 0.30 0.30 BSC2F8 11/12/2013 CC 0.27 0.27 11
  • 12. Thermogravimetry analysis was carried out to relate the effect of Fe substitution in place of Co on conductivity behavior of BSCF series… Temperature dependence weight losses for 1273 K sintered BSCF compositions CC GC Weight loss (%) GC BSC8F2 1.41 1.01 BSC6F4 2.28 0.83 BSC4F6 11/12/2013 CC 2.28 0.95 BSC2F8 2.30 1.63 12
  • 13.     Single phase cubic Ba0.5Sr0.5Co1−xFexO3−δ compositions were synthesized by gel-combustion and cation complexation routes. As Co gets replaced by Fe, cell parameters decreased systematically. Electrical conductivity of BSCF samples initially increased with temperature through a maximum and then decreased with further rise in temperature. This attributed to the loss of lattice oxygen. Fe substitution has very little effect on overall electrical conductivity. But still, there is need to increase overall conductivity of BSCF compositions to get good performance cathode for current state-of-the art IT-SOFCs. 11/12/2013 13
  • 14.  Measurement of thermal expansion coefficient  Study of chemical compatibility with different electrolyte materials  Increase the electronic conductivity  Study composite cathode materials 11/12/2013 14
  • 15. Acknowledgement … Dr. T. Mukherjee Dr. D. Das Dr. S. R. Bharadwaj Dr. B. N. Wani Dr. S. Varma Mr. A. N. Shirsat Mr. Ganesh Mane Mr. Suhas Phaphale All my collaborators, office staff and other people with whom I interacted during these works BARC-Mumbai University Collaboration Scheme, DAE for financial grant & providing a solid platform to carry out my research work 11/12/2013 15
  • 16. 11/12/2013 16

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