Materials and Preparation Methods for Miniaturized Solid ...µ-Solid Oxide Fuel Cell System Heat...

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

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M a t e r i a l s



Outline

• Motivation

• µ - Fuel Cell Systems

• µ - Solid Oxide Fuel Cell Hot Plate

Pulsed Laser DepositionSpray Pyrolysis

ElectrolyteCathodeAnode & Current Collector

• Acknowledgement

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M a t e r i a l s



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



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

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M a t e r i a l s



Outline

• Motivation

• µ - Solid Oxide Fuel Cell System




• Acknowledgement

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M a t e r i a l s



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

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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)

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µ-SOFC test unitcathodecurrent collector

cathode

anodeelectrolyte

substrateanodecurrent

collector

1-5 µm

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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.

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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

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Outline

• Motivation





• Acknowledgement

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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)

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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

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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.

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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.

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Outline

• Motivation





• Acknowledgement

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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

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Film Formation

500 µm 5 µm10 µm500 µm

T1 < T2 < T3 < T4

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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

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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


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Outline

• Motivation





• Acknowledgement

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M a t e r i a l s



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.

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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)


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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


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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−

−⎛ ⎞− = − −⎜ ⎟

⎝ ⎠

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• 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−

−⎛ ⎞− = − −⎜ ⎟

⎝ ⎠


Microstrain and Grain Growth of nano- Ce0.8Gd0.2O1.9-x


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M a t e r i a l s



• 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.


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


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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

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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

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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

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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

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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

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M a t e r i a l s



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

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-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

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M a t e r i a l s



• 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



Outline

Motivation: µ - Solid Oxide Fuel Cell & One-Bat Project

µ - Solid Oxide Fuel Cell System

µ - Solid Oxide Fuel Cell Hot Plate


ElectrolyteCathodeAnode & current collector

Acknowledgement

37

M a t e r i a l s



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

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M a t e r i a l s



La0.6Sr0.4Co0.2Fe0.8O3 by PLD

saphire substrate

200 nm

200 nm

A. Infortuna; Nonmetallic Materials ETH Zurich

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M a t e r i a l s



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


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M a t e r i a l s



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 %


41

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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


volume diffusion

log D

surface diffusion


volume diffusion


42

M a t e r i a l s



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


43

M a t e r i a l s



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!


44

M a t e r i a l s



Outline






Acknowledgement

45

M a t e r i a l s



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



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


volume diffusion

1/T

log D

surface diffusion


volume diffusion

log D

surface diffusion


volume diffusion

precursor0.1 mol/l NiNO3 x 6H2O


47

M a t e r i a l s



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


timegr

ain

size

Ni

CGO

grai

nsi

ze

Ni

CGO

48

M a t e r i a l s



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


49

M a t e r i a l s


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


Nonmetallic Inorganic Materials, ETH ZurichFIB preparation of TEM specimens

e-beamTEM


51

M a t e r i a l s



Ni-CGO anode

substrate

Ni-CGO-porosity

Me-support layer

300 nm


52

M a t e r i a l s



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



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



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


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



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



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

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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


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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

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Outline






Outlook

Acknowledgement

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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

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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


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Free standing triple layer

After etching After annealing at 600 °C

Light microscope view from backside on anode (light shining through)

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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)

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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

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Outline




Pulsed Laser Deposition Spray Pyrolysis


Acknowledgement

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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)

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