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
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2. overview …
 Renewable Energy and Fuel Cells
 Solid Oxide Fuel Cells
 Cathode for SOFC
 Synthesis
 Characterization
 Electrical Conductivity
 Conclusions
 Future Work
 Acknowledgement
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3. Renewables in energy production …
Introduction to Fuel Cells …
•
•
•
•
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Based on hydrogen technology
High efficiency, Low pollutant
Sustainable fuel resources
Energy-environment issues
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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
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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)
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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
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Label
BSC2F8
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6. Gel-combustion (GC)
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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+
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0.53
0.61
Fe3+
0.64
Co2+
0.74
Fe2+
0.78
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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
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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
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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
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10. CC
GC
Specific Conductivity σ, Scm-1 (at 723 K)
GC
BSC8F2
20.27
38.86
BSC6F4
18.73
33.04
BSC4F6
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CC
37.95
32.82
BSC2F8
25.64
31.91
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11. Activation energy (eV) (400-700 K)
GC
BSC8F2
0.37
0.42
BSC6F4
0.33
0.39
BSC4F6
0.30
0.30
BSC2F8
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CC
0.27
0.27
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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
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CC
2.28
0.95
BSC2F8
2.30
1.63
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13. 
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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.
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14.  Measurement of thermal expansion coefficient
 Study of chemical compatibility with different electrolyte materials
 Increase the electronic conductivity
 Study composite cathode materials
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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
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