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  • 1. Effect of Ca2+ substitution on the structural, thermal and electrical properties of BiYO 3 for SOFC applications Presented by Samita Thakur, O. P. Pandey, K. Singh School of Physics & Materials Science At IV th International Conference on Advances in Energy Research Indian Institute of Technology Bombay, Mumbai Copyright 2013-2014 Thapar University, Patiala
  • 2. Copyright 2013-2014
  • 3. Conventional Energy sources We use energy every day. Energy is needed to operate machines, to heat and cool our homes and schools, to cook, to provide light and to take people from place to place. Coal Petroleum Copyright 2013-2014 Natural Gas Nuclear power plants THAPAR UNIVERSITY, PATIALA 3 Wednesday, December 11,
  • 4. Copyright 2013-2014
  • 5. Copyright 2013-2014 Green House Emission
  • 6. Copyright 2013-2014 Solutions to Energy Problem
  • 7. Copyright 2013-2014 Non-conventional energy sources
  • 8. A fuel cell is a device that converts chemical energy into electrical energy, water, and heat through electrochemical reactions. The voltage generated by a single cell is typically rather small (< 1 volt), so many cells are connected in series to create a useful voltage. Copyright 2013-2014 Fuel Cells
  • 9. Fuel cells operation dc current Heat Oxygen Hydrogen Water Catalyst (Pt) Anode (-) H2 2H 2e Catalyst (Pt) Cathode (+) Copyright 2013-2014 Membrane (Nafion)
  • 10. Copyright 2013-2014 Types of Fuel Cells
  • 11. Copyright 2013-2014 Electric power for household supply Practical Applications of Fuel Cells THAPAR UNIVERSITY, PATIALA 11 Wednesday, December 11,
  • 12. Copyright 2013-2014 THAPAR UNIVERSITY, PATIALA 12 Wednesday, December 11,
  • 13. Merits of SOFc Solid oxide fuel cells (SOFCs) are attracting attention due to following reasons:  Higher efficiency  Negligible environmental pollution  No liquid electrolyte  Least material corrosion Copyright 2013-2014  Offers good fuel flexibility  Internal reformation of hydrocarbons fuels THAPAR UNIVERSITY, PATIALA 13 Wednesday, December 11,
  • 14. Copyright 2013-2014 Components of SOFC THAPAR UNIVERSITY, PATIALA 14 Wednesday, December 11,
  • 15. Copyright 2013-2014 Working Principle of SOFC THAPAR UNIVERSITY, PATIALA 15 Wednesday, December 11,
  • 16. Limitations of SOFC The high temperature limits applications of SOFC units and they tend to be rather large Assembling Maintenance Design Cost & choice of material THAPAR UNIVERSITY, PATIALA 16 Wednesday, December 11, Copyright 2013-2014 High operating temperature also enhance the degradation rate of materials
  • 17. Remedies for the problems (1) Increase the choices for materials selection (3) Lower the degradation of materials, cost and increase the durability Lowering of operating temperature will also increase the resistance of the cell and reduces the overall output. So, there is need to develop new material s . THAPAR UNIVERSITY, PATIALA 17 Wednesday, December 11, Copyright 2013-2014 Lowering of operating temperature (2)
  • 18. Motivation of the present work  The best known solid electrolytes for SOFC are ceramics with fluorite type structure, materials based on zirconia and ceria. But its conductivity falls down drastically below 800 C. The major drawback associated with ceria based electrolytes is the conversion of Ce4+ to Ce3+ under SOFC anodic conditions (reducing atmosphere). This results in high electronic conduction and chemical expansion  One class of materials that exhibits high oxide ion conductivity is based upon the perovskite structure. Sr2+ doped LaInO3, LaYO3, LaGaO3 have been exploited as S/cm.  Depending upon the above stated facts we have chosen Bi1-xCaxYO3 (x=0, 0.1) to study its structural, thermal and electrical properties as electrolyte for SOFC applications. THAPAR UNIVERSITY, PATIALA 18 Wednesday, December 11, Copyright 2013-2014 electrolytes for their oxide ion conductivity with conductivity in the range of 10-3
  • 19. Synthesis of Bi1-xCaxYO3 (x=0, 0.1) Bi2O3 CaO Y2O3 Homogeneous mixture Calcination at 750 0C Copyright 2013-2014 Pelletization and sintering at 800 0C THAPAR UNIVERSITY, PATIALA 19 Wednesday, December 11,
  • 20. X-ray Diffraction (b) Intensity (counts/s) 4000 2000 0 (a) 4000 2000 0 30 40 50 60 70 80 Copyright 2013-2014 20 2 (degree) Figure 1: X-ray diffraction pattern of (a) BiYO3 (b) Bi0.9Ca0.1YO3. THAPAR UNIVERSITY, PATIALA 20 Wednesday, December 11,
  • 21. Differential scanning calorimetry/Thermogravimetric analysis 0.3 (a) (b) 100.0 100.0 98.8 100 200 300 400 500 600 700 800 0.1 0.0 99.2 -0.1 100 Temperature ( C) 99.6 200 300 400 500 600 700 800 Temperature ( C) Copyright 2013-2014 -0.3 0.2 Weight (%) 99.2 0.0 Microvolt (endo-down) 99.6 0.3 Weight (%) Microvolt (endo-down) 0.6 Figure 2: DSC/TGA curve of (a) BiYO3 (b) Bi0.9Ca0.1YO3 THAPAR UNIVERSITY, PATIALA 21 Wednesday, December 11,
  • 22. Thermal expansion coefficient 0.008 0.008 12 (b) (a) 9 0.006 9 0.006 0.002 6 0.002 ( 10-6 C-1) 3 0.004 L/L0 0.004 ( 10-6 C-1) L/L0 6 3 0 0.000 0.000 -3 100 200 300 400 500 600 700 100 800 200 300 400 500 600 700 0 800 Temperature ( C) Copyright 2013-2014 Temperature ( C) THAPAR UNIVERSITY, PATIALA 22 Wednesday, December 11,
  • 23. Ac impedance spectroscopy 2 (b) (a) 470 C (a) (b) 0 12000 Ln ( T) 8000 Z'' ( ) -2 -4 -6 4000 -8 0 -10 0.8 0 4000 8000 12000 16000 1.0 1.2 1.4 1.6 1.8 1000/T (K-1) Z' ( ) Cole –Cole plot of (a) BiYO3 (b) Bi1-xCaxYO3. Copyright 2013-2014 Arrhenius curves of (a) BiYO3 (b) Bi1-xCaxYO3. THAPAR UNIVERSITY, PATIALA 23 Wednesday, December 11,
  • 24. ConclusionS  Rietveld refinement confirms that samples are single phase and exhibit pm-3m symmetry.  The thermogravimetric analysis shows that samples exhibit weight loss at high temperatures due to the creation of oxygen vacancies and bismuth vitalization.  The TEC and conductivity shows two different slopes one be due to the increase in oxygen vacancy concentration and hence increase in mobility of defects at high temperatures. THAPAR UNIVERSITY, PATIALA 24 Wednesday, December 11, Copyright 2013-2014 below 550 C and other above that. This change in slope can
  • 25. Copyright 2013-2014 In today’s world, solving environmental and energy problems is an investment, not an expense THAPAR UNIVERSITY, PATIALA 25 Wednesday, December 11,