Oxidische Materialien: ZrO 2 Jürgen Janek Carsten Korte, Ilia Valov, Robert Klein, Andreas Peters Bjoern Luerßen, Holger Fischer, Eva Mutoro Marcus Rohnke,

Oxidische Materialien: ZrO2

Jürgen Janek

Carsten Korte, Ilia Valov, Robert Klein, Andreas Peters

Bjoern Luerßen, Holger Fischer, Eva Mutoro

Marcus Rohnke, Sebastian Meiss

Funding: DFG, FCI, BASF AG DFG-Schwerpunktprogramm 1136

www.chemie.uni-giessen.de/home/janek

24.06.2005AG Janek – Oxidische Materialien: ZrO2

ZrO2 als elektrokeramisches Material

• Die Elektrolytmembran (Energietechnologie)HT-Brennstoffzellen (SOFC) . . . . . Grenzflächenchemie

. . . . . unkonventionelle Brennstoffe

• Das Sensormaterial (Sensortechnologie)Elektrochemische SensorenIonische Langmuir-Sonden . . . . . . . . Plasmaanalytik

• Die Ionenpumpe (Oberflächenchemie/Plasmachemie)Elektrochemische Promotion . . . . . . smart surfacesIonenpumpen für Plasmen . . . . . . . . Plasmatechnologie

• Neue Materalien (und Funktionen…)Substitution/Dotierung . . . . . . . . . . . Stickstoffionenleiter

. . . . . . . . . . Lumineszenz . . . . . . . . . . Nanoskalige Multischichten


ZrO2(+Y2O3) – Die „Nernstmasse“


ZrO2(+Y2O3) – Die Nernstlampe


Chemistry

EngineeringPhysics

Solid State Ionics – Open questions?

Bulk properties/phenomena:- Equilibrium defect structures- Non-equilibrium defects (low-T)- New electrolytes - Optimisation of functional materials

Interfacial phenomena:- surfaces of ionic solids- solid/solid electrodes- kinetics of inner boundaries- interfaces plasma/ionic material

Galvanic cells:- new sensors- new fuel cells/batteries- thermovoltaics

Methods:- in situ spectroscopy/microscopy- microelectrodes- micro- and nano-ionics


Electrochemical surface control

Electrochemical generation of „spillover“ species- e. g. oxygen on platinum- e.g. sodium on platinum

many studies - but no in situ studies on microscopic details

Electrochemical „Switching“ of catalysts MeOx on YSZ

- thin films of oxides (PLD)

- e. g., Fe2O3 → Fe3O4 → Fe1-xO → Fe

no investigations yet (to our knowledge…)


Electrochemical surface control

24,0 s22,8 s22,0 s21,2 s20,4 s19,6 s18,8 s18,0 s

0 s

350 µm

diffusion coefficient of atomic oxygen: DO[Pt(111), 200°C] = 5.2·106 cm2/s

diffusion coefficient corresponding to work function front: D[Pt(111), 400°C] 5·105 cm2/s

T = 400 °Cp(O2) = 10-5 mbar YSZ surfacePt surfacePt surface


interface

bulkd

Gr

Vol

electrolyte

insulator

2 (Gr

– Vol

) ≈ 2 Gr

if Gr

Vol

Vol

Gr

1/d

2 (Gr

– Vol

)

1/

Ionic conductivity vs. layer periodicity

interface

bulkelectrolyte

Ionic transport in boundary regions


Vol

Gr

1/d

2 (Gr

– Vol

)

1/

Overlap of space charge regions,strong increase in conductivity

c( )VAn /

dd = δd > δ d < δ

[1] Sata, Eberman, Eberl und Maier, Nature 408, 946-949 (2000)[2] Sata, Jin-Philipp, Eberl und Maier, Solid State Ionics 154-155,

497-502 (2002)

(in the case of CaF2/BaF

2 für d > 50 nm)

or

structural disorder,small change of σ

Gr

with periodicity

c( )VAn /

dd = δd > δ d < δ



systems:

ZrO2(+ 12 mol% CaO) / Al

2O

3

● high concentration of mobileoxygen vacancies

● small Debye length, lD ≈ 10 nm

Target-halter

Konvex-linse

Laserstrahl(248 nm)

Turbopumpe undDrehschieberpumpe

Gaseinlass mitDruckregelung

Plasma

Target

Substrat-heizung

Substrat

500 nm

Al2O

3

Al2O

3

ZrO2

500 nm

2 µm

Al2O

3

ZrO2/Al

2O

3

SEM images U

porousPt-electrode

porousPt-electrode

I

jO2-

½ O2 + 2 e– = O2– O2– = ½ O

2 + 2 e–

substrate

Pulsed Laser Deposition:

500 nm



conductivity increases with 1/d by 2 orders of magnitude

Interface:2δσ

Gr ≈ 2,4 · 10-9 S (600 °C)

δ < 10-9 m(TEM results)

σGr

≈ 1,2 · 10-2 S/cm (600 °C)

cf. σVol

≈ 6,0 · 10-6 S/cm

about 4 orders of magnitude

ZrO2 (+ 12 mol% CaO) / Al

2O

3

40 nm100 nm200 nm 50 nm67 nm 33 nm

co

nduc

tivity

reciprocal thickness



Ion emission from YSZ

Y. Torimoto et al., Jpn. J. Appl. Phys. 36 (1997) L238Y. Fujiwara at al., J. Electrochem. Soc. 150 (2003) E117


Ion pumping into plasmas

~

13.56 MHz

O2 O2 O

O

Ion emission

Ion desorption

YSZ

Plasma


Optisches System:- Nd:YAG gepumter Farbstofflaser (10 Hz / 355 nm)- Farbstoff : 1:1 Mischung Coumarin 47/ 120 - Filter : (846 + 3) nm

Parallelplattenentladung:- kapazitiv, asymmetrisch- f = 13,56 MHz max. Ueff ~ 600 V

Arbeitsgas : Sauerstoff- p = 5 - 100Pa- Gasfluß = 3 - 10 sccm

Electrodes:- radius r = 40 mm, - distance d = 15 - 100 mm

Resolution: axial: - max. shift 100 mm,- min. step size 0,3 mm, - min. distance beam-electrodes 0,5 mm

radial:- max. shift 76 mm,- min. sep size 1 mm

Institut für PhysikUniversität Greifswald


TALIF-Experiment


axial position / mm

0 10 20 30 40 50

fluor

esce

nce

inte

nsity

/ a

.u.

0.0

0.5

1.0

1.5

grounded, U = 0 VU = -0,5 VU = - 10 VU = + 10 VU = +10 V


oxygen atom density

M. Rohnke, S. Peters, J. Janek and J. Meichsnersubmitted to J. Appl. Phys. (2004)

YSZ electrode

steel electrode


(Zr,Y)(N,O)2 – A nitrogen electrolyte

1 cm

as-deposited

annealed at 700 °C for 15 min

15 min at 700 °C

applied voltage U = -2.2V

as-deposited films show dark violet color

SIMS analysis proofs that nitrogen remains in YSZ after annealing (i.e. the violet color is related to reduction of YSZ)

YSZ single crystal(111)or(100)

+



0 1000 2000 3000 400010-4

10-3

10-2

10-1

100

101

single crystal YSZ/ N-YSZ (+18O)/ YSZDeposition temperature - 500 °CLayer thickness - approx. 1 µm

90

Zr14

N /

90Z

r16O

Depth / nm

as-deposited(500 °C deposition temperature)

18O

/ (1

6O +

18O

)

YSZ/AlYSZ/Al22OO33

MultilayersMultilayers100nm/layer100nm/layer

YSZ/AlYSZ/Al22OO33

MultilayersMultilayers100nm/layer100nm/layer

YSZYSZ


0 500 1000 150010-4

10-3

10-2

10-1

100

101

YSZ/N-YSZ (+18O)/YSZAnnealed at 700 °Ct = 15 min.

18O

/ (18

O +

16O

)

90

Zr14

N /

90Z

r16O

Depth / nm


thermally annealed700 °C, 15 min

18O

/ (1

6O +

18O

)


0 1000 2000 3000 4000 5000

Ag/YSZ/N-YSZ (+18O)/YSZ/AgT = 700 °Ct = 15 min.U = -2.2 V

18O

/ (18

O +

16O

)

Depth / nm


field experiment700 °C for 15 minU = -2.2 V 1

8O / (

16O

+ 1

8O)

oxygen is much faster than nitrogen

The applied electric field influences the nitrogen profile…


Dr. Marcus RohnkeDr. Bjoern Luerssen Bernhard Franz

Boris Mogwitz Dr. Carsten Korte

Ilia Valov Robert Klein

Klaus Peppler Eva Mutoro

Dr. Doh-Kwon LeeHolger FischerAndreas PetersSebastian MeißClaus C. Fischer

Prof. Jürgen Janek

24.06.2005AG Janek – Oxidische Materialien: ZrO2www.chemie.uni-giessen.de/home/janek

Documents

Oxidische Materialien: ZrO 2 Jürgen Janek Carsten Korte, Ilia Valov, Robert Klein, Andreas Peters Bjoern Luerßen, Holger Fischer, Eva Mutoro Marcus Rohnke,