Korea-America nano forum
Effect of Starting Materials on the Characteristics
of (La1-xSrx) Mn1+yO3-δ Powder Synthesized by GNP
2007. 04. 26
MI-Jai Lee
orea
nstitute of
eramic
ngineering &
echnology
Principle
What is SOFC ?
Solid oxide fuel cell is energy
conversion device that produces
electricity by electrochemical.
It operate at high temperature
over 600℃ with pollution-free
technology.
Anode : H2+O-2 = H2O + 2eCathode : 1/2O2 + 2e- = O-2
Total : H2 +1/2O2 = H2O
Electronic Materials Team
Principle
Advantage & Disadvantage
Advantage
z Highest energy conversion efficiency
z No need to use noble metal catalyst
(600~1000℃ operation)
Disadvantage
z Not reliable to thermal cycle
z Low physiochemical stability
z LNG, coal gas can be used
z No problems of electrolyte loss
z High quality byproduct heat
z Modular construction
z Potential for cogeneration
z Much lower production of pollutants.
Electronic Materials Team
Principle
Key Research Material Areas ?
General Materials
• Nano-scale materials, and synthesis
- Nano-powders
- Composites
• New cathode materials
- Higher conductivity
- Lower polarization
• Fuel flexible anode materials
- Sulfur tolerance
- Various fuels
Materials Processing
• Thin films
- lower temperatures
- new processes
• Chemical synthesis routes for
development of mixed conductors
• Investigation of complex perovskitetype oxides
• MEA fabrication and characterization
(solid acids, proton conducting
oxides)
Electronic Materials Team
Experimental Procedure
La
Sr
Mn
(1mole or 1.4mole)
Nitrate, Oxide
solution
HNO3
Chemical Reaction of
Glycine-Nitrate Process
(a) Carboxylic Acid Group
Mixing
H2N - CH2 - C
Addition
(Glycine)
- Sr2+
O
(b) Amine Group
Complexation
H
H
O
N - CH2 - C
Combustion
OH
(H2O)5La2+
Calcination
(400~1200℃ )
(La0.8Sr0.2)MnO3 Powder
O
2+
O
XRD
BET
Thermal
conductivity detctor
Sr H2N - CH2 - C
OH
(H2O)6-x
x
Initial stage of glycine-metal
complexation in an queous solution.
Electronic Materials Team
Result
DT-DSC curve of synthesized La0.8Sr0.2MnO3 powder
(Stoichiometric)
Combustion of residual glycine
0.4
100
211.8℃
0.2
70
-0.6
919.4℃
-0.8
-16.75 J/g
60
590.9℃
-148.1 J/g
50
400
600
Temperature (℃)
(a) Nitrate solution
-0.4
70
-0.6
580.9℃
-55.32 J/g
-1.0
-1.2
1000
-0.2
80
60
Organic
disappearance
800
TG (%)
-0.4
Dehydration
1200
0.2
18.48%
0.0
-0.2
DSC (mW/mg)
TG (%)
80
0.0
206.6℃
←Exo DSC (mW/mg)
NO3- or CO3 21.79%
disappearance
0.4
90
←Exo
90
200
100
-0.8
905.1℃
-9.196 J/g
-1.0
50
-1.2
200
400
600
800
Temperature (℃)
1000
1200
(b) Oxide solution
Electronic Materials Team
Result
La0.8Sr0.2MnO3
XRD patterns of (La0.8Sr0.2)MnO3 powder
(Stoichiometric)
Sr2MnO4
La2O3
Sr(NO3)2
1000℃
800℃
400℃
As-synthesized
20
30
40
50
2Θ (degree)
60
70
10
80
20
30
40
50
60
70
80
2Θ (degree)
(a) Nitrate solution
(b) Oxide solution
100
COO
+
NH3
80
Mol %
10
-
60
Under pH < 1, Amine
group are only existing.
40
20
0
0
2
4
6
8
pH
10
12
14
Electronic Materials Team
Result
XRD patterns of (La1-xSrx)Mn1.40O3 powders
(Non-Stoichiometric, Nitrate Solution)
(LaSr)MnO3
Secondary
phase
)
t
i
n
u
.
b
r
a
(
y
t
i
s
n
e
t
n
I
calcined at 1200℃
calcined at 1000℃
as-synthesized
20
30
40
50
60
70
80
2Θ (degree)
It has single phase after calcination at 1200℃ for 4hrs.
(La0.8Sr0.2)Mn1.4O3
Electronic Materials Team
Result
Electrical conductivity of (La0.8Sr0.2)Mn1-xO3 powders
2.5
2.8
Nitrate
Oxide
Nitrate
Oxide
2.4
2.0
log(σ · S/cm)
log(σ /S· cm)
2.4
1.6
1.2
2.3
2.2
0.8
2.1
0.4
0.0
2.0
0.9
1.0
1.1
1.2
1.3
1.4
1.5
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1000/T K-1
1000/T K -1
(a) Stoichiometric (Mn = 1mole)
(b) Non-Stoichiometric (Mn = 1.4mole)
Nitrate solution : 4.87 S/cm at 700℃
Oxide solution : 35.7 S/cm at 700℃
Nitrate solution : 210.3 S/cm at 700℃
Oxide solution : 152.7 S/cm at 700℃
Temp.(℃)
σ (S/cm)
Refs.
800
180
Solid State Ionics 110(1998)61
900
155
J. Mater. Chem. 1997, 7(13)
Electronic Materials Team
Result
Temperature programmed reduction (Non-Stoichiometric)
H2 uptake amount (A.U. unit)
(a)
(b)
100
200
300
400
500
600
700
o
T em perature( C )
Temperature programmed reduction of La0.8Sr0.2Mn1-xO3 powder
after calcination 1000℃ for 4hrs with different starting Materials.
(a) nitrate and (b) Oxide
Electronic Materials Team
Conclusion
Effect of Starting Materials on the Characteristics of
(La1-xSrx)Mn1+yO3-δ Powder Synthesized by GNP
• Case1 : Nitrate solution (La:Mn=1:1)
- LSM powders show secondary phases after calcination at 1000℃ (La 2O3, Sr2MnO4)
- Average particle size is 0.90 ㎛ and BET is 26.5 m2/g
- The particles show porous structure
- Electrical conductivity shows 4.87 S/cm at 700℃ after sintered at 1200℃
• Case2 : Oxide solution (La:Mn=1:1)
- Average particle size is 9.04㎛ and BET is 16.8 m2/g
- LSM powders show a secondary phase Sr2MnO4 after calcination 1000℃ for 4hrs.
- Electrical conductivity shows 35.7 S/cm at 700℃ after sintered at 1200℃ for 4hrs.
• Case3 : Mn excess (La:Mn=1:1.4, nitrate solution)
- Average particle size is 2.46 ㎛
- The powders have good sinterability
- Deoxidization peak of the synthesized (La,Sr)MnO3+δ powders using nitrate solution appeared
at lower temperature than the synthesis powders using oxide solution, at 450℃(β-peak)
- Electrical conductivity shows 210.3 S/cm at 700℃ after sintered at 1200℃ for 4hrs.
Electronic Materials Team