materials and preparation methods for miniaturized solid ...µ-solid oxide fuel cell system heat...
TRANSCRIPT
1
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Department MaterialsDepartment MaterialsETH ETH ZurichZurich
SwitzerlandSwitzerland
Materials and Preparation Methods Materials and Preparation Methods for for
Miniaturized Solid Oxide Fuel CellsMiniaturized Solid Oxide Fuel Cells
ETH ETH ZurichZurich
L. J. Gauckler, U. ML. J. Gauckler, U. Müücke, D. Beckel, J. cke, D. Beckel, J. RuppRupp & A. Infortuna& A. Infortuna
2
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Outline
• Motivation
• µ - Fuel Cell Systems
• µ - Solid Oxide Fuel Cell Hot Plate
Pulsed Laser DepositionSpray Pyrolysis
ElectrolyteCathodeAnode & Current Collector
• Acknowledgement
3
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
ONEBAT Project Goals
• Very high energy capacity (at least 3 times more than current batteries)• Immediate charging (using compressed gas as a fuel)• Power network and geographical independence
The goal of the ONEBAT project:
Miniaturized solid oxide fuel cell (SOFC) technology for small portable electronic applications such as cellular phones.
⎟⎟⎠
⎞⎜⎜⎝
⎛=
anodepcathodep
qkTOCV
O
O
2
2ln4
&
4
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Systems Energy Densities
• Values as announced by system developers• µ-PEFC lays very high but metal hydride technology is not down-scalable• All the published energy density values for µ-DMFC are significantly lower than
press releases statements (e.g. “5 times longer run-time than Li-ion“...)
0
200
400
600
800
1000
1200
0 200 400 600 800 1000 1200
Specific Energy (Wh/kg)
Ener
gy D
ensi
ty (W
h/l)
µ -SOFC
µ -DMFC
µ-PEFC
Li-ion
Ni-MH
5
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Outline
• Motivation
• µ - Solid Oxide Fuel Cell System
• µ - Solid Oxide Fuel Cell Hot Plate
Pulsed Laser DepositionSpray Pyrolysis
ElectrolyteCathodeAnode & Current Collector
• Acknowledgement
6
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Scientific and technological objectives
SOFC pack with µ-fuel-cell with:
• 1 W continuous power (5 W peak) within 30 cm3 (incl. 15 cm3 fuel)
• operating directly on liquid gas (e.g. butane)
• reaching an unprecedented battery capacity ( 1000 Wh/litre & 1000 Wh/kg )
• integrating fuel cell on the chip using micro-fabrication technology
7
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
µ-Solid Oxide Fuel Cell System
Heat losses Electric Power
Exhaust Gas
Fuel CellFC
Fuel ReformerRF
Fuel Air
Heat ExchangerHX
Post Combustor PC
Hot Module HM
ThermalManagement
Ambientconditions
~550 °C
The hot module consists of four subsystems: the fuel cell (FC), the fuel reformer (RF), heat exchanger (HX), and the post combustor (PC)
8
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
µ-SOFC test unitcathodecurrent collector
cathode
anodeelectrolyte
substrateanodecurrent
collector
1-5 µm
9
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
SnO2 sensor array on micro-hot plate by MIMIC
10 µm
M. Heule, L. J. GaucklerSensors and Actuators B 93 (2003) 100–106
Test hotplates with 20 two-point contacts.
10
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Heat loss from micro-hotplates.
65 mW are sufficient to heat a 300 x 300 µm2 membrane to 500 °Cτ = 10-20 ms
M. Heule, L. J. Gauckler, Adv. Mater. 13, No. 23, 1790-93, 2001
heating cooling
300 µm
11
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Outline
• Motivation
• µ - Solid Oxide Fuel Cell System
• µ - Solid Oxide Fuel Cell Hot Plate
Pulsed Laser DepositionSpray Pyrolysis
ElectrolyteCathodeAnode & Current Collector
• Acknowledgement
12
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Focusing LensWindow
Deposition Chamber
Target
Plume
Laser Beam
Substrate
Substrate Heater
Target Rotator
Pulsed Laser Deposition
•KrF Excimer Laser: λ = 248 nm
• Energy: ~2 J/cm2
•Frequency: 5-10 Hz
PLD-Experimental
Typical PLD Synthesis Method• Targets synthesized by solid state techniques• Films deposited
•at room temperature•In high vacuum (~10-3 mTorr) or •50-100 mTorr O2 (dynamic)
13
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
RT, 20 m Torr 600°C, 20 m Torr 600°C, 200 m Torr400°C, 50 m Torr
PLD of CGO and YSZ Films: Influence of pressure
14
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
1E-3 0.01 0.10
100
200
300
400
500
600
CeO2 by PLD CGO20 by PLD
subs
trate
tem
pera
ture
(°C
)
pressure (mbar)
epitaxial
polycrystalline
amorphous10nm 20nm 50nm
particlesno coherent filmcracks
crack free(100) oriented
20nm no cracks
CGO prepared by PLDA. Infortuna, L. J. Gauckler, Thin Solid Films, in press, 2005andTrtik, V., et al. Appl Phys A, 1999. 69: p. S815-S818.Norton, D.P., et al. Appl, Phys Lett, 1999. 74(15): p. 2134.
15
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
PLD preparation of 8-YSZ films
A. Infortuna, L. J. Gauckler, Thin Solid Films, in press, 2005andTrtik, V., et al. Appl Phys A, 1999. 69: p. S815-S818.Norton, D.P., et al. Appl, Phys Lett, 1999. 74(15): p. 2134.
16
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Outline
• Motivation
• µ - Solid Oxide Fuel Cell System
• µ - Solid Oxide Fuel Cell Hot Plate
Pulsed Laser DepositionSpray Pyrolysis
ElectrolyteCathodeAnode & Current Collector
• Acknowledgement
17
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Electrostatic Spray Deposition
ElectrostaticTaylor cone & multi cone mode
~1000 V/cm
stable situation
with E field: Instabilitymulti-coneTaylor-cone
IR Pyrometer
High Voltage
Needle
Solution
Substrate and YSZ Film
Spray
Heating Plate
Pump
A.M. Ganan-Calvo et al., Journal of Aerosol Science, 28, 249 (1997).
C.H. Chen et al., Journal of Materials Chemistry, 6, 765 (1996).D. Perednis et.al.; Thin Solid Films; 474 ; 84-95; 2005
0.10.1Concentration [mol/l]
Zr(C6H7O2)4YCl3·6H2O
Zr(C6H7O2)4YCl3·6H2OSalts
50% C2H5OH50% C8H18O3
50% C2H5OH50% C8H18O3
Solvent [vol.%]
Air blast
Air
SolutionAir blast
Air
Solution
18
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Film Formation
500 µm 5 µm10 µm500 µm
T1 < T2 < T3 < T4
19
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
ANODENi-YSZ
ELECTROLYTEYSZ
CATHODELa0.6Sr0.4Co0.2Fe0.8
O3
Cross-section of the fuel cell
Dense electrolyte with thickness of 500 nm on porous anode support substrateGrain size 30-50 nm
Perednis, D.; Wilhelm, O.; Pratsinis, S.E.; Gauckler, L. J.;Thin Solid Films (474) ; 84-95 ; 2005
anode support
cathode screen printedelectrolyte YSZ
20
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Tape cast electrolyte:Ce0.8Sm0.2O1.9 - x (240 µm)
Thick Ceria Tape: M.Gödickemeier and L.J.Gauckler, J. Electrochem. Soc., 145, 414 (1998).
Sprayed composite electrolyte:Ce0.8Y0.2O1.9 – x (0.25 µm)
YSZ (0.25 µm)
Ce0.8Y0.2O1.9 – x (0.25 µm)
0 200 400 600 800 10000
100
200
300
400
500
600
Pow
er [m
W/c
m2 ]
Cell Current [mA/cm2]
Thick Ceria Tape
Thin Ceria Film
Improved power output due to multilayer electrolyte of Ce0.8Y0.2O1.9/Zr0.85Y0.15O1.925/Ce0.8Y0.2O1.9
Cell with CeO2ss / YSZ / CeO2ss composite electrolyte
700°C
Perednis, D.; Wilhelm, O.; Pratsinis, S.E.; Gauckler, L. J.;Thin Solid Films (474) ; 84-95 ; 2005
21
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Outline
• Motivation
• µ - Solid Oxide Fuel Cell System
• µ - Solid Oxide Fuel Cell Hot Plate
Pulsed Laser DepositionSpray Pyrolysis
ElectrolyteCathodeAnode & Current Collector
• Acknowledgement
22
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
200 nm 200 nm
Spraypyrolysisfilms
Ce0.8Gd0.2O1.9-x films CeO2 film
Ce0.8Gd0.2O1.9-x CeO2
Spray pyrolysis and PLD thin filmsCeO2 and CGO
A. Infortuna, L. J. Gauckler, Thin Solid Films, in press, 2005
PLD film
200 nm
Ce0.8Gd0.2O1.9-x
Substrate sapphire.
23
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
XRD patterns of YSZ film deposited on Inconel 600 at 275°C, annealing time 15 minutes
As deposited films are amorphous
Amorphous→crystalline transition onset at ∼ 450°C
20 25 30 35 40
0
100
200
300
400
700600
500450
400350
300250
2θ [°]Tem
perat
ure [°
C]C
ount
s/s111
200
Crystallization of SP films by thermal treatment
450°CI. Kosacki et al, Solid State Ionics, 136-137, 1225 (2000)
325°CC. Laberty-Robert et al, Materials Research Bulletin, 36, 2083 (2001)
CrystallineT. Nguyen et al, Solid State Ionics, 138, 191 (2001)
Perednis, D.; Wilhelm, O.; Pratsinis, S.E.; Gauckler, L. J.;Thin Solid Films (474) ; 84-95 ; 2005
24
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
0.5 1/Å
50 nm
TEM Diffraction Pattern TEM Dark Field Image
YSZ film on Inconel 600 after annealing at 700°C for 2 hrs
⇒ Grain Size ∼10 nm⇒ Crystalline
Nano-crystalline microstructure
Perednis, D.; Wilhelm, O.; Pratsinis, S.E.; Gauckler, L. J.;Thin Solid Films (474) ; 84-95 ; 2005
25
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Model of limiting grain size holds for grains below 120 nmParabolic grain growth law holds for µm grains
Thermal stability of Ce0.8Gd0.2O1.9-x
J. Rupp, Nonmetallic Materials ETH Zurich, Acta Mat, in press, 2005
self limittinggrain growth
Ostwald ripeningparabolic grain growth
0 10 20 300
20406080
100120140160180200220240260280
dwell time (h)
grai
n si
ze (n
m)
600°C700°C800°C900°C
1000°C
1100°C
1200°C
0 0( )n nD D k t t− = −
0
0 0( ) ( ) 1 expt t
LD t D D D τ−
−⎛ ⎞− = − −⎜ ⎟
⎝ ⎠
26
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
• Microstrain and grain growth cease within first 10hrs of isothermal dwell.• Both properties follow exponential laws with a characteristic relaxation time τ
D0 = start grain size, D = grain size, DL = limiting grain size.
-5 0 5 10 15 20 25 30 35-10
0
10
20
30
40
50
60
70
80
Mic
rost
rain
* 1
0 3
Dwell time [h]
600° C 700° C 900° C
Microstrain of Ce0.8Gd0.2O1.9-x
0 expt
LD τε ε−
= +
spray pyrolysis films
-5 0 5 10 15 20 25 30 350
10
20
30
40
50
60
Ave
rage
gra
in s
ize
[nm
]
Dwell time [h]
600° C 700° C 800° C 900° C
Grain growth of Ce0.8Gd0.2O1.9-x
0
0 0( ) ( ) 1 expt t
LD t D D D τ−
−⎛ ⎞− = − −⎜ ⎟
⎝ ⎠
spray pyrolysis films
Microstrain and Grain Growth of nano- Ce0.8Gd0.2O1.9-x
J. Rupp, Nonmetallic Materials ETH Zurich, Acta Mat, in press, 2005
27
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
• Increasing T (600-900°C) results in faster grain growth + faster microstrain relaxation
Self limitting grain growth. Metastable nanosized microstructures establishes.
• At higher T ( > 1100° C) fast microstrain relaxation and Ostwald ripening of grains.
Parabolic grain growth ; not limited anymore.
spray pyrolysis films
Characteristic times for grain growth and strain relaxation of of nano- Ce0.8Gd0.2O1.9-x prepared by spray pyrolysis
Ostwaldripening
strain relaxation Energy
amorphous
nano-crystallinesingle crystal
500 600 700 800 900 1000 1100 1200 1300
0
2
4
6
8
10
12R
elax
atio
n tim
e τ
[h]
Dwell temperature [° C]
Strain Grain growth
J. Rupp, Nonmetallic Materials ETH Zurich, Acta Mat, in press, 2005
28
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Influence of tripple junction mobility (γtj) on GG kinetics can not be neglected for very smallgrains like in nano-materials.
3πθ = 2
2cos 1tj
gb
Dγ θαγ θ
= =−
1, 0
1,3
α θ
πα θ
<< →
>> →Normal parabolic gg:
Small grains, small γtj:
Straight grain boundariesGG ceases !
*Gottstein G. and Shvindlerman L.S., Acta materialia. 50, 703, 2002*Weygand D., Brechet Y., Lepinoux J., Acta materialia. 46, 6559, 1998*Gottstein G., Ma Y., Shvindlerman L.S., Acta materialia. 2005, in press
Neumann relation holds.
αn =
num
bero
f gra
insi
des
t
d
dL
Limiting Grain Growth due to Grain Size
t
d
29
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
6 7 8 9 10 11 12
e-46
e-45
e-44
e-43
e-42
e-41
e-40
1200 1000 800 600
Temperature [° C]
1E-46
1E-45
1E-44
1E-43
1E-42
1E-41
10000 / Temperature [K]
xrd sem
1E-40
Gra
in b
ound
ary
mob
ility
[m3 /N
s] 01exp Qk k M
R T⎛ ⎞= − ∝⎜ ⎟⎝ ⎠
activation energy
d=grain sizen=grain growth exponentt=timeR=gas constant T=temperatureγ=grain boundary energy=0.3J/m2 (*)
Activation energy ~1.13 eV for nm grain sized CGOgrain boundary diffusion
Grain boundary mobilityThermal stability of Ce0.8Gd0.2O1.9-x
J. Rupp, Nonmetallic Materials ETH ZurichActa Mat, in press, 2005
30
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
200 nm
200 nm
200 nm
200 nm
1000° C
1100° C
Undoped CeO2 Ce0.8Gd0.2O1.9-x
Fast grain growth in CeO2 filmsSlow grain growth in Ce0.8Gd0.2O1.9-x due to solute drag.
Spray pyrolysis thin films.
Influence of doping on Grain GrowthJ. Rupp, Nonmetallic Materials ETH Zurich
31
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
0 5 10 15 20 2512
14
16
18
20
22
24
26
28
30
Aver
age
grai
n si
ze [n
m]
Dwell time [h]
CeO2 CGO
Spray pyrolysis thin films.
Stable microstructures after first 10 h of isothermal dwell.
700° C
Influence of doping on Grain GrowthJ. Rupp, Nonmetallic Materials ETH Zurich
32
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
amorphous crystalline grain growth
• nucleation and growth• free volume change & shrinkage
dens films
•normal grain growth•self limitting grain growth
∆V
log Dlog D
1/T
log Dlog D
1/T
volumediffusion
gbdiffusion
surface diffusiont
d
dL T1=const.
T2=const.
shrinkage due togb diffusion
nucleation and growth,shrinkage due togb & volume diffusion
•self limiting grain growth
0 0( )n nd d k t t− = −
•parabolic grain growth
Microstructural evolution:CGO thin films
0
0 0( ) ( ) 1 expt t
LD t D D D τ−
−⎛ ⎞− = − −⎜ ⎟
⎝ ⎠
J. Rupp, Nonmetallic Materials ETH ZurichActa Mat, 2005
strain relaxation
33
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
8 10 12 14 16 18 20 22 24 261E-9
1E-8
1E-7
1E-6
1E-5
1E-4
1E-3
0.01
0.1
1
10
1000 800 600 400 200
bulk (this work)pld, 60 nm (this work)spray, 80nm (this work)sputtered, 30 nm (Bieberle et al.)
1.01 eV
0.90 eV
0.78 eV
0.98 eV
T [°C]
Con
duct
ivity
[S/m
]
10000 / T [K]
0.97 eV
• Nanocrystalline Ce0.8Gd0.2O1.9-x thin films show lower ionic conductivity comparedto microcrystalline bulk samples due to large amount of GB.
measured inair
Electrical properties of Ce0.8Gd0.2O1.9-x
J. Rupp, Nonmetallic Materials ETH Zurich; Acta Mat,in press, 2005
34
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
-35 -30 -25 -20 -15 -10 -5 00.01
0.1
1
10
100
log
σ [S
/m]
log pO2 [atm]
810°C 701°C 608°C 500°C
~60 nm
1/6
1/6
¼
¼
-35 -30 -25 -20 -15 -10 -5 00.1
1
10
100
1000
log
σ [S
/m]
log pO2 [atm]
900°C 800°C 700°C 600°C
~80 nm
¼
¼
¼
¼
-35 -30 -25 -20 -15 -10 -5 00.1
1
10
100
800° C700° C600° C500° C
log
σ [S
/m]
log pO2 [atm]
~5 µm
¼
¼¼
1/6
PLD Spray pyrolysis Bulk
• Thin film and bulk Ce0.8Gd0.2O1.9-x are predominantly ionic conductors for T < 600°C, with high enough ionicconductivity to operate as electrolytes in a SOFC system.
• Thin film microstructures are very stable after pre-annealinglow electrical conductivity degradation.
Electrical properties of Ce0.8Gd0.2O1.9-x Films & BulkJ. Rupp, Nonmetallic Materials ETH ZurichActa Mat, 2005
J. Rupp, Nonmetallic Materials ETH Zurich; Acta Mat, in press, 2005
35
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
• Ce0.8Gd0.2O1.9-x and CeO2 gets more easily reduced with decreasing grain size below ~400 nm
CeO2
100 1000 100001E-21
1E-20
1E-19
1E-18
1E-17
1E-16
1E-15
1E-14
1E-13
Spin coated film, Suzuki (2002) PLD film, this work Spray pyrolysis film, this work Bulk, Kleinlogel (2000) Bulk, Gödickemeir (1996) Bulk, this work
EDB
700°
C (
atm
)
Average grain size [nm]
-5.5
Ce0.8Gd0.2O1.9-x
Electrolytic Domain Boundary of Ce0.8Gd0.2O1.9-x and CeO2 Thin Films
J. Rupp, Nonmetallic Materials ETH ZurichActa Mat, in press, 2005
36
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Outline
Motivation: µ - Solid Oxide Fuel Cell & One-Bat Project
µ - Solid Oxide Fuel Cell System
µ - Solid Oxide Fuel Cell Hot Plate
Pulsed Laser DepositionSpray Pyrolysis
ElectrolyteCathodeAnode & current collector
Acknowledgement
37
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Cathode Materials
• PLD La0.6Sr0.4Co0.2Fe0.8O3 Thin Films
• Spray Pyrolysis La0.6Sr0.4Co0.2Fe0.8O3 Thin Films
D. Beckel; Nonmetallic Materials ETH Zurich
38
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
La0.6Sr0.4Co0.2Fe0.8O3 by PLD
saphire substrate
200 nm
200 nm
A. Infortuna; Nonmetallic Materials ETH Zurich
39
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Ratio of Substrate Temperature to Solvent Boiling Point forSP La0.6Sr0.4Co0.2Fe0.8O3
Crack free continuous film
Cracks in film
Powdersno continuous film
20 µm
20 µm
20 µmLSCF deposited at
Deposition parameters:30 ml / h, 0.02 mol / l,
60 min, 1 bar.Films annealed
int
1.15 (in K) Deposition
SolventBoilingPo
TT
=
TDep = 255 °C, TSBP = 180 °C
TDep = 190 °C, TSBP = 130 °C
TDep = 225 °C, TSBP = 155 °C
Ratio of deposition temperature to solvent boiling point most important.
0
50
100
150
200
250
300
350
400
450
0 50 100 150 200 250 300
Solvent boiling point / °C
Dep
ositi
on te
mpe
ratu
re /
°C
D. Beckel; Nonmetallic Materials ETH Zurich
40
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
SP La0.6Sr0.4Co0.2Fe0.8O3 films: microstructures after annealing
600 °C 700 °C
800 °C 900 °C
LSCF after 3hannealing with
varying annealingtemperature on Si.
Deposition parameters:255 °C, 1 bar, 30 ml / h,
0.04 mol / l, 30 min.Heating rate 2 °C / min.
1
500 nm 500 nm
500 nm 500 nm
Pores form and coalesce depending on annealing temperature.
30%20%
6 %
D. Beckel; Nonmetallic Materials ETH Zurich
41
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Sintering and pore coalescence during annealing of SP deposited films
grain growth and pore formation & growthno shrinkage , no densification
grain growth and shrinkage
∆V
La0.6Sr0.4Co0.2Fe0.8O3 films
CGO films
interfacial energy γ LSCF/sobstrate =large„de-wetting“
interfacial energy γ CGO/substrate =small„wetting“
1/T
log D
surface diffusion
grain boundary diffusion
volume diffusion
1/T
log D
surface diffusion
grain boundary diffusion
volume diffusion
log D
surface diffusion
grain boundary diffusion
volume diffusion
D. Beckel; Nonmetallic Materials ETH Zurich
42
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Consequences of Pore Coalescence I (grain size ~ film thickness)La0.6Sr0.4Co0.2Fe0.8O3
• Pore coalescence → islands with low connectivity.• Isolated islands do not contribute to conductivity.• Electric conductivity should decrease upon pore coalescence for larger grain
sizes.
top view
substrate
side view
D. Beckel; Nonmetallic Materials ETH Zurich
43
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Electric conductivity of La0.6Sr0.4Co0.2Fe0.8O3 films on sapphire annealed at different temperatures
Higher annealing temperatures lead to more pore coalescence and island with low connectivity, thus to lower conductivity
and at T> 950 °C to second phase!
D. Beckel; Nonmetallic Materials ETH Zurich
44
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Outline
Motivation: µ - Solid Oxide Fuel Cell & One-Bat Project
µ - Solid Oxide Fuel Cell System
µ - Solid Oxide Fuel Cell Hot Plate
Pulsed Laser DepositionSpray Pyrolysis
ElectrolyteCathodeAnode & current collector
Acknowledgement
45
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
cathodecurrent collector
cathode
anodeelectrolyte
substrateanodecurrent
collector
The µ-SOFC
1-5 µm
Ni-CGO anode thin film and a Ni current collector operating at 550°C.
U. Mücke; Nonmetallic Materials ETH Zurich
46
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Deposition of pure NiO Filmssubstrate500 µm tape casted YSZ
200 µm 400 nm 400 nm
2 µm
reduced @ 700°C for 1 hr
as deposited annealed at 800 °C for 10 hrs annealed at 1000 °C for 10 hrs
400 nm
1/T
log D
surface diffusion
grain boundary diffusion
volume diffusion
1/T
log D
surface diffusion
grain boundary diffusion
volume diffusion
log D
surface diffusion
grain boundary diffusion
volume diffusion
precursor0.1 mol/l NiNO3 x 6H2O
U. Mücke; Nonmetallic Materials ETH Zurich
47
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
CGO and Ni growth model: Two step annealing
NiO-CGO Ni-CGO
air H2
T,t
time
grai
nsi
ze
T3
T2T1
time
grai
nsi
ze
T3
T2T1
coarsening of NiO and CGO coarsening of Ni only
U. Mücke; Nonmetallic Materials ETH Zurich
timegr
ain
size
Ni
CGO
grai
nsi
ze
Ni
CGO
48
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Conductivity Data of 60/40 Ni/CGO Anode Layers
• σ=f(t) in a mixture of dry H2:N2
• sample remains conductive after 1 cycle => metallic conductivity
0 10 20 30 40 50 60 70 8010-4
10-3
10-2
10-1
100
101
102
103
104
105
106
conductivity [S/m] temp [°C]
time [h]
cond
uctiv
ity [S
/m]
13470 S/m
0
100
200
300
400
500
600
700
temp [°C
]
Pratihar et al. 1993for µ-sized Ni
U. Mücke; Nonmetallic Materials ETH Zurich
49
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH ZurichFIB preparation thin films for TEM
M. Holzer, EMPA and U. Mücke; Nonmetallic Materials ETH Zurich
50
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH ZurichFIB preparation of TEM specimens
e-beamTEM
M. Holzer, EMPA and U. Mücke; Nonmetallic Materials ETH Zurich
51
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Ni-CGO anode
substrate
Ni-CGO-porosity
Me-support layer
300 nm
M. Holzer, EMPA and U. Mücke; Nonmetallic Materials ETH Zurich
52
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Ni support
300 nm
NiCGO porosity
substrate
M. H
olzer, EMPA and U
. Mücke; N
onmetallicM
aterials ETH Zurich
53
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Elec
tron
Bea
mEl
ectr
on B
eam
Ion BeamIon Beam
y
z
x
5252ºº St
age T
ilt
Stag
e Tilt
~ 2 µm
AutomationAutofocusDriftcompensation (z-dir.)
FIB – Nanotomography / FEI Strata DB235
54
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Z-spacing10-30nm
z
z
z
FIB
y
SEM
xy
x50-100 nm!
x
Image processingfor 3D reconstruction
M. Holzer, EMPA Zurich
55
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH ZurichQuantitative Analysis:Skeletonization Network analysis Topology
1.6
µm
M. Holzer, EMPA Zurich
56
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
10 nm
Ni grain size distribution from 3D-data M. Holzer, EMPA Zurich
1.6 µm
Skeletonization + Distance maps
1.6 µm
Skeletonization + Distance maps
57
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Conductivity Data of 60/40 Ni/CGO Anode Layers
σ=f(T, Xi) and σ= f (Ni-grain size& distribution)U. Mücke; Nonmetallic Materials ETH Zurich
0 10 20 30 40 50 60 70 8010 -4
10 -3
10 -2
10 -1
100
101
102
10 3
10 4
10 5
10 6
conductivity [S/m]
temp [°C]
time [h]
cond
uctiv
ity [S
/m]
13470 S/m
0
100
200
300
400
500
600
700
temp [°C
]
Pratihar et al. 1993
for µ -sized Ni
0 10 20 30 40 50 60 70 8010 -4
10 -3
10 -2
10 -1
100
101
102
10 3
10 4
10 5
10 6
conductivity [S/m]
temp [°C]
time [h]
cond
uctiv
ity [S
/m]
13470 S/m
0
100
200
300
400
500
600
700
temp [°C
]
Pratihar et al. 1993
for µ -sized Ni
ρ/ρ0
1 10 100 103 104 nm
10
8
6
4
2
e- free path λ ≈ 100 to 200 nmρ/ρ0
1 10 100 103 104 nm
10
8
6
4
2
ρ/ρ0
1 10 100 103 104 nm
10
8
6
4
2
58
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Ni + Ni/CGO Composite Layer
• porous Ni as current collector on Ni-CGO layer?
• annealed @ 600 °C for 1 hrs with 1°C up, then 1 hr in 5% H2 in N2 and 2°C down
400 nm800 nm
top view cross section
YSZ substrate
NiO-CGO
NiO
YSZ
Ni-CGO
Ni
U. Mücke; Nonmetallic Materials ETH Zurich
59
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH ZurichElectrochemical Characterization:Cathode/Electrolyte/Anode Tri-Layer
0.8 1.0 1.2 1.4
-8-7-6-5-4-3-2-101234567
800 600 400
T [°C]
EA = 1.12 eV
EA = 1.61 eV
EA = 1.56 eV
ln R
p [Ωcm
2 ]
1000/T [1/K]
anode cathode electrolyte total resistance
EA = 1.03 eV
Measurement Techniques:
• 4 point conductivity
• impedance spectroscopy
@ T = 550°C:
Rp electrolyte = 0.05 Ωcm2
Rp anode = 1.5 Ωcm2
Rp cathode = 8.4 Ωcm2
predicted performance
(Ecell = 0.7 V, H2/air):
P = 50 mW/cm2 @ T = 550°C
P = 600 mW/cm2 @ T = 650°C
measured performance
P = 600 mW/cm2 @ T = 720°C
Bieberle, Rupp, Beckel, Mücke, Gauckler, mstnews, in print, June, 2005
60
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Outline
Motivation: µ - Solid Oxide Fuel Cell & One-Bat Project
µ - Solid Oxide Fuel Cell System
µ - Solid Oxide Fuel Cell Hot Plate
Pulsed Laser DepositionSpray Pyrolysis
ElectrolyteCathodeAnode & current collector
Outlook
Acknowledgement
61
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Substrates for free standing ceramic membranes
First tests with NiO-CGO anodes
Free standing triple layer (anode, electrolyte, cathode)
200 – 1000 nm
100 – 500 µm
800 – 3000 nm
100 – 500 µm
substarte substarte
62
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Free Standing 60/40 NiO/CGO Membranes
• membranes can up to now withstand– sudden heating up to 600 °C without rupturing– normal handling in lab
• size can be up to 0.5 x 0.5 mm2
membrane after heat treatment at 450 °Cmembrane after spraying and etching
U. Mücke; Nonmetallic Materials ETH Zurich
63
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Free standing triple layer
After etching After annealing at 600 °C
Light microscope view from backside on anode (light shining through)
64
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Free standing NiO/CGO anodes
After etching(light microscope,
view from backside)
After annealing at 600 °C(SEM top view, high voltage to make membranes transparent)
65
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
CGO Membranes with electrodes on Si
Ce0.8Gd0.2O2 electrolyteMembrane thickness: 400 nmLargest Membrane: 1 mmStable up to 350 °C.
600 µm version
LCLC EPFLEPFL
Paul Muralt, N. Setter; EPFL
66
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Outline
Motivation: µ - Solid Oxide Fuel Cell & One-Bat Project
µ - Solid Oxide Fuel Cell System
µ - Solid Oxide Fuel Cell Hot Plate
Pulsed Laser Deposition Spray Pyrolysis
ElectrolyteCathodeAnode & current collector
Acknowledgement
67
M a t e r i a l s
Swiss Federal Institute of TechnologyZürich
Nonmetallic Inorganic Materials, ETH Zurich
Daniel BeckelAnja Bieberle Brandon Bürgler
Eva Jud
Jörg Richter
Michel PrestatAnna InfortunaJenny Rupp
Ulrich Mücke
• INSTITUT FÜR MIKROSYSTEMTECHNIK, NTB, BUCHS• Züricher Hochschule Winterthur• Ceramics Laboratory , EPF- Lausanne• Laboratory of Thermodynamics in Emerging
Technologies (LTNT), ETH Zürich
• KTI (CH)