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Barium Doped Bismuth Vanadate Structural and Thermal Properties for SOFC

Application 

Sakshi Gupta and K. Singh* 

School of Physics & Materials Science, Thapar University, Patiala

*E-mail: kusingh@thapar.edu

Paper Code: 099

IV th International Conference on Advances in Energy Research

Indian Institute of Technology Bombay, Mumbai

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Introduction

Deficiency of conventional energy sources.

Release of green house gases with combustion of conventional energy sources.

Need to develop an energy efficient non conventional eco- friendly source.

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Fuel Cell

Fuel cell is an electrochemical energy conversion device.

It produces electricity from external supplies of fuel (anode

side) and oxidant (cathode side).

In fuel cell and battery, electrochemical reactions are used to

create electric current.

Fuel cells are different from batteries as they consume reactant,

which can be replenished, while batteries store electrical energy

chemically in a closed system.

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Types of Fuel Cells

4

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Alkali Fuel Cell (AFC)

Compressed hydrogen and oxygen fuel

potassium hydroxide (KOH) electrolyte

~70% efficiency

150˚C - 200˚C operating temp.

300W to 5kW output

Requires pure hydrogen fuel and platinum catalyst Liquid filled container → corrosive leaks

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Molten Carbonate Fuel Cell (MCFC)

Carbonate salt electrolyte

60 – 80% efficiency

~650˚C operating temp.

cheap nickel electrode catalyst

up to 2 MW constructed, up to 100 MW designs exist

Corrosive electrolyte

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Phosphoric Acid Fuel Cell(PAFC)

Phosphoric acid electrolyte

37-42% efficiency

150˚C - 200˚C operating temp

11 MW units have been tested

The electrolyte is very corrosive

Platinum catalyst is very expensive

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Polymer electrolyte Membrane(PEM)

Thin permeable polymer sheet electrolyte

40 – 50% efficiency

50 – 250 kW

80˚C operating temperature

Electrolyte will not leak or crack

Temperature good for home or vehicle use

Platinum catalyst on both sides of membrane

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Solid Oxide Fuel Cell (SOFC)

Hard ceramic oxide electrolyte

~80% efficient

~1000˚C operating temperature

cells output up to 100 kW

High temp / catalyst can extract the hydrogen from the fuel at the electrode

High temp allows for power generation using the heat, but limits use

SOFC units are very large

Solid electrolyte have no leakage problem

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Continued.....

Out of the fuel cells discussed above Solid Oxide

Fuel Cells (SOFCs) can be considered as a possible

solution. SOFCs provide high total efficiency in

addition to clean energy production. As well as water

is the only emission along with energy along with

energy when hydrogen is used as fuel in SOFCs

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The benefits of SOFCs Include:

Energy security: reduce oil consumption, cut oil imports, and increase the amount of the country’s available electricity supply.

Reliability: achieve operating times in excess of 90% and power available 99.99% of the time.

Low operating and maintenance cost: the efficiency of the SOFC system will drastically reduce the energy bill (mass production) and have lower maintenance costs than their alternatives.

Constant power production: generate power continuously.

Choice of fuel: allow fuel selection: hydrogen may be extracted from natural gas, propane, butane, methanol or diesel fuel.

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desirable characteristics of SOFC components:

Good stability. High conductivity. Chemical compatibility with other components of the cell. Similar thermal expansion coefficient to avoid cracking during the cell operation. Dense electrolyte to prevent gas mixing. Porous anode and cathode to allow gas transport to the reaction sites. High strength and toughness Compatibility at higher temperatures. Low cost.

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Characteristics of Solid Electrolyte

Availability of large number of free ions

Large number of vacancies for hopping

Free of porosity

Thermal expansion match

Chemically stable (at high temperatures as well as in

reducing and oxidizing environments)

The ionic conductivity of the electrolyte should be high

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METHODOLOGY

Bi2O3 + V2O5 + BaO

Grinding of required composition in agate mortar pestle

Splat quenching of the melted sample

Melting at 1250 �C

Characterizations

XRD Dilatometery SEM

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X-RAY DIFFRACTION ANALYSIS

Reitveld refined XRD patterns of Bi4V2-xBaxO11-δ (a) as quenched x = 0.0, (b) as quenched x = 0.05, (c) sintered x= 0 and (d) sintered x = 0.05.

20 30 40 50 60 70 80

(b)

degrees (2)

Inte

nsity

(arb

. uni

ts)

(a)

20 30 40 50 60 70 80

(d)

Inte

nsity

(arb

. uni

ts)

degrees (2)

(c)

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Reitveld refined lattice parameters of Bi4V2-xBaxO11-δ

(x = 0.0 and 0.05)

Composition

As quenched samples Sintered samples

a (Å) b (Å) c (Å) β (degrees) a (Å) b (Å) c (Å) β (degrees)

Bi4V2O11-δ

5.58

15.35 16.59 89.98 5.59 15.33 16.59 89.97

Bi4V1.95Ba0.05O11-δ

 5.57 15.39 16.65 90.08 5.59 15.35 16.61 89.95

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MICROSTRUCTURE ANALYSIS

0.0 0.055

10

15

20

25

30

35

Range (m

)

x

Grain size range of sintered samples with x = 0.0 and 0.05.

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SEM Micrographs

(a) (b)

(c) (d)

Scanning electron micrographs of Bi4V2-xBaxO11-δ (a) as quenched x = 0.0, (b) as quenched x = 0.05, (c) sintered x= 0.0 and (d) sintered x = 0.05.

20 μm 20 μm

10 μm10 μm

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DILATOMETRIC ANALYSIS

Thermal expansion curves Bi4V2-xBaxO11-δ (a) as quenched x = 0.0, (b) as

quenched x = 0.05, (c) sintered x= 0.0 and (d) sintered x = 0.05.

0 100 200 300 400 500 600 700

0.0

1.0x10-3

2.0x10-3

3.0x10-3

4.0x10-3

5.0x10-3

6.0x10-3

Temperature(C)

L/Lo

-2.0x10-6

0.0

2.0x10-6

4.0x10-6

6.0x10-6

8.0x10-6

1.0x10-5

(C

TE /C

)

(b)

0 100 200 300 400 500 600 700 800-1.0x10-3

0.0

1.0x10-3

2.0x10-3

3.0x10-3

4.0x10-3

5.0x10-3

6.0x10-3

7.0x10-3

Temperature (C)

L/Lo

(a)

-4.0x10-6

-2.0x10-6

0.0

2.0x10-6

4.0x10-6

6.0x10-6

8.0x10-6

1.0x10-5

(CTE / C

)

0 100 200 300 400 500 600 700 800

0.0

1.0x10-3

2.0x10-3

3.0x10-3

4.0x10-3

5.0x10-3

6.0x10-3

Temperature (C)

L/Lo

-2.0x10-6

0.0

2.0x10-6

4.0x10-6

6.0x10-6

8.0x10-6

1.0x10-5

(C

TE /C

)

(c)

0 100 200 300 400 500 600 700 800

0.0

1.0x10-3

2.0x10-3

3.0x10-3

4.0x10-3

5.0x10-3

6.0x10-3

(d)

Temperature (C)

L/Lo

-2.0x10-6

0.0

2.0x10-6

4.0x10-6

6.0x10-6

8.0x10-6

1.0x10-5

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Thermal expansion coefficients and different transitiontemperatures of Bi4V2-xBaxO11-δ (x = 0.0 and 0.05)

Composition  

As quenched samplesTEC  (10-6 /⁰C)

Sintered samplesTEC (10-6

/⁰C)

Remarks

As quenched samples Sintered samples

Bi4V2O11-δ 8.83 8.98 α→β and β→γtransitions take place at 405 ⁰C and within the range 447-595 ⁰C respectively.

β→γ transition take place at533 ⁰C 

Bi4V1.95Ba0.05O11-δ 9.21 8.62 α→β and β→γtransitions take place within the range at 301-398 ⁰C and 414- 509 ⁰C resp.

α→β and β→γ transitions takeplace within the range at330-392 ⁰C and 477- 595 ⁰C resp.

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Conclusions

• All the samples synthesized are found to be single phase.

• All the samples are found to be stabilized in α phase with

C2/m space group which is confirmed with Reitveld

refinement.

• The grain size of the samples is decreasing with doping.

• The thermal expansion coefficient found to be in the range of

the components which are used in SOFC.

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Acknowledgement

• I would like thank Department of Science and Technology

(DST) for the financial support.

• I would like to thank my Supervisor Dr. Kulvir Singh

(Professor and Head) School of Physics and Materials Science,

Thapar University, Patiala for his Guidance.

• I would like to thank Dr. P.C. Ghosh (Organizer ICAER 2013)

for providing me an opportunity to present my work here.

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