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
24.06.2005AG Janek – Oxidische Materialien: ZrO2
ZrO2(+Y2O3) – Die „Nernstmasse“
24.06.2005AG Janek – Oxidische Materialien: ZrO2
ZrO2(+Y2O3) – Die Nernstlampe
24.06.2005AG Janek – Oxidische Materialien: ZrO2
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
24.06.2005AG Janek – Oxidische Materialien: ZrO2
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…)
24.06.2005AG Janek – Oxidische Materialien: ZrO2
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
24.06.2005AG Janek – Oxidische Materialien: ZrO2
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
24.06.2005AG Janek – Oxidische Materialien: ZrO2
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
Ionic transport in boundary regions
24.06.2005AG Janek – Oxidische Materialien: ZrO2
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
Ionic transport in boundary regions
24.06.2005AG Janek – Oxidische Materialien: ZrO2
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
Ionic transport in boundary regions
24.06.2005AG Janek – Oxidische Materialien: ZrO2
Ion emission from YSZ
Y. Torimoto et al., Jpn. J. Appl. Phys. 36 (1997) L238Y. Fujiwara at al., J. Electrochem. Soc. 150 (2003) E117
24.06.2005AG Janek – Oxidische Materialien: ZrO2
Ion pumping into plasmas
~
13.56 MHz
O2 O2 O
O
Ion emission
Ion desorption
YSZ
Plasma
24.06.2005AG Janek – Oxidische Materialien: ZrO2
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
Ion pumping into plasmas
TALIF-Experiment
24.06.2005AG Janek – Oxidische Materialien: ZrO2
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
Ion pumping into plasmas
oxygen atom density
M. Rohnke, S. Peters, J. Janek and J. Meichsnersubmitted to J. Appl. Phys. (2004)
YSZ electrode
steel electrode
24.06.2005AG Janek – Oxidische Materialien: ZrO2
(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)
+
24.06.2005AG Janek – Oxidische Materialien: ZrO2
(Zr,Y)(N,O)2 – A nitrogen electrolyte
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
24.06.2005AG Janek – Oxidische Materialien: ZrO2
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
(Zr,Y)(N,O)2 – A nitrogen electrolyte
thermally annealed700 °C, 15 min
18O
/ (1
6O +
18O
)
24.06.2005AG Janek – Oxidische Materialien: ZrO2
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
(Zr,Y)(N,O)2 – A nitrogen electrolyte
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…
24.06.2005AG Janek – Oxidische Materialien: ZrO2
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