Fantastic Tales of Super Ceramics
Professor M. L. Mecartney
Department of Chemical Engineering and Materials Science
University of California, Irvine
My Research Group
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Ph.D. Students
 Peter Dillon
 Tiandan Chen
 Sungrok Bang
 Lynher Ramirez
M.S. Students
 Kevin Olson

Undergraduate Students
 Daniel Strickland (NSF
REU)
 Joy Trujillo (UC LEADS)
 Jeremy Roth (SURP)

External Collaborators
 Professor Trudy Kriven,
University of Illinois
 Professor Susan
Krumdieck, University of
Canterbury, NZ
How I found ceramic science,
and discovered a life
I was once a lowly Classics major, studying Greek
and Latin at Case Western Reserve University….
Then I discovered Materials Science and
Engineering – Solid State Physics and Physical
Chemistry!!!
Undergraduate research on positron annihilation
in alumina (in Physics) and single crystal
deformation of ZrO2 (in MSE)
Post B.S./B.A. Wanderings
Graduate school – M.S. and Ph.D. in Materials Science and
Engineering at Stanford University (BaTiO3 and Si3N4)
Post-doctoral research – Max-Plank-Institut in Stuttgart,
Germany (ZrO2)
Faculty positions – University of Minnesota, Minneapolis,
then University of California, Irvine (LiNbO3,
Pb(Zr,Ti)O3, V2O5, CaO-B2O3-SiO2, (Sr,Ba)Nb2O6, etc.)
Fantastic Ceramics
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Did you know that ceramic conductors are a
critical part of fuel cell technology?
Did you know that ceramics can be stronger
than any other material?
Did you know that ceramics can be deformed
just like metals?
Did you know that ceramics can conduct
electricity without any resistance?
Super Ceramics
Super ionic conductors for fuel cells
 Super strong ceramics for cutting
applications
 Super plastic ceramics for net shape
forming
 NO CERAMIC SUPERCONDUCTORS
IN THIS TALK
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CERAMICS
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A ceramic is a compound composed of at least
one metallic and non-metallic element
Ionic/covalent bonding
Most Ceramics are Crystalline
ZrO2
NaCl
Typical Grain / Grain Boundary Structure
H.L. Tuller: “Ionic conduction in nanocyrstalline materials.” Solid State Ionics 146, 157 (2000).
Ceramics as Ionic
Conductors
OVERVIEW OF FUEL CELL TYPES
e
Load
Depleted fuel and
product gases out
SOFC
Depleted oxidant and
product gases out
H2
O
O2
O2
H2O
PEMFC
and
PAFC
H2
H+
MCFC
H2
CO2
H2O
CO3
H2 O
O2
CO2
Oxidant in
Fuel in
Anode
Electrolyte
(ion conductor)
Cathode
From Dr. Jack Brouwer NFCRC
Brick Layer Model
Polycrystalline Material Model
Equivalent Circuit Model
Modified From S M. Haile, D L West, and J. Campbell, J .Mater. Res. vol 13, pp.1576-1595 (1998).
AFM of YSZ Film on Al2O3
R.M. Smith, X.D. Zhou, W. Huebner, and H.U. Anderson (2004), "Novel Yttrium-Stabilized Zirconia
Polymeric Precursor for the Fabrication of Thin Films," Journal of Materials Research, 19, 2708-2713.
15X Conductivity Increase
in Nano-crystalline Zirconia!
H.L. Tuller: “Ionic conduction in nanocyrstalline materials.” Solid State Ionics 146, 157 (2000).
Increase in GB Conductivity
X. Guo and Z.L. Zhang (2003), "Grain Size Dependent Grain Boundary Defect Structure: Case of Doped Zirconia," Acta Materialia, 51, 2539-2547.
Propoxide Sol-Gel TF Preparation
Polymer Precursors
Yttrium
Isopropoxide
Stabilizer Conc (mol%):
4Y / 8Y / 4Sc / 8Sc / 4Y:4Sc
Preparation
Scandium
Isopropoxide
Zirconium
Propoxide
Characterization
Solution in Isopropanol à
0.2M Alkoxide Concentration
SEM Characterization:
Grain Size + Film Thickness
Hydrolysis:
70wt% HNO3, 30 wt% H2O
Spin Coat on Si / Al2O3 Substrate
2000RPM, 45s
DSC / TGA Analysisà
Determine Tvap - Tpyrolysis – Tcrystallization
TEM Characterization:
Grain Size + Composition
Glancing Incidence XRD (GID):
Grain Size + Crystal Structure
Evaporate Alcohol / H2O
Bake à Pyrolize + Crystallize
Impedance Spectrometry:
Ionic Conductivity à Bulk / Grain / Grain Boundary
Acetate Sol-Gel TF Preparation
Polymer Precursors
Yttrium
Acetate
Stabilizer Conc (mol%):
4Y / 8Y / 4Sc / 8Sc / 4Y:4Sc
Preparation
Scandium
Acetate
Zirconium
Acetate
Characterization
Solution in Methanol
SEM Characterization:
Grain Size + Film Thickness
Add GPC to Allow Process to Be
Carried Out in Open Air
Hydrolize with Ethylene Glycol
Adjust Viscosity à
Add Methanol to 20 cP
TEM Characterization:
Grain Size + Composition
Spin Coat on Si / Al2O3 Substrate
3000RPM, 60s
DSC / TGA Analysisà
Determine Tvap / Tpyrolysis / Tcrystallization
Glancing Incidence XRD (GID):
Grain Size + Crystal Structure
Evaporate Alcohol à Form Gel
Bake à Pyrolize + Crystallize
Impedance Spectrometry:
Ionic Conductivity à Bulk / Grain / Grain Boundary
Adapted From: R.M. Smith, X.D. Zhou, W. Huebner, and H.U. Anderson (2004), "Novel Yttrium-Stabilized Zirconia
Polymeric Precursor for the Fabrication of Thin Films," Journal of Materials Research, 19, 2708-2713.
Multiple Spin Coated Layers
(Ba-Ti on Si Wafer)
M.C. Gust, N.D. Evans, L.A. Momoda, and M.L. Mecartney, "In-Situ Transmission Electron Microscopy Crystallization Studies
of Sol-Gel Derived Barium Titanate Thin Films," J. Am. Ceram. Soc. 80 [11] 2828-36 (1997).
Cross Sectional SEM
ZrO2 Thin Film on Si Wafer
Typical Grain Size of ZrO2
Burning Questions
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Will our nanocrystalline zirconia thin films
be a super ionic conductor when compared
to zirconia with a larger grain sizes?

And why?
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Stay tuned for Daniel Strickland’s talk at
the end of the summer!
High Strength
Ceramics
50%Al2O3-25%NiAl2O4-25%ZrO2
Fine Grain Ceramics Are Strong,
But…

At high temperatures, the smaller the grain
size, the easier to deform a material
(creep).

These materials were developed to be high
speed cutting tools, the tips of which may
reach 1500°C.

Will creep be a problem????
Compression Test Results
True Strain
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
5000
10000
15000
20000
25000
30000
Time (s)
50%Al2O3-25%NiAl2O4-25%TZP @ 1425C
50%Al2O3-25%NiAl2O4-25%TZP @ 1350C
35000
50% Al2O3-25%NiAl2O4-25%TZP
Undeformed
Average Grain Size (mm)
Al2O3:
0.76
NiAl2O4 :
0.49
TZP:
0.42
50% Al2O3-25%NiAl2O4-25%TZP
Deformed at 1425°C
Average Grain Size (mm)
Al2O3:
1.39
NiAl2O4 :
0.81
TZP:
0.62
Stress Response
Strain Rate (1/s)
1.E-03
1.E-04
1.E-05
1.E-06
10
100
Stress (MPa)
50%Al2O3-25%NiAl2O4-25%TZP @ 1425C
50%Al2O3-25%NiAl2O4-25%TZP @ 1350C
Fine Grain Ceramics May be
Super Strong at Room
Temperature…
….but very deformable and soft at
high temperatures.
Superplastic Ceramics
Superplasticity
The ability of polycrystalline solids to exhibit greater than 100%
elongation in tension, usually at elevated temperatures about 0.5Tm
Constitutive Law

Q 

ε  A p exp  
d
 RT 
n
Where:
έ
Strain rate
σ Stress
n Stress exponent
d
Grain size
p Grain size exponent
Q Activation energy
Rg Gas constant
T
Temperature (K)
J.Wakai, Adv. Ceram. Mater., 1986
Applications
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SPF enables net-shape-forming, fabricate unique complex
shapes from a single piece of materials;
Eliminates parts and process steps, minimizes manufacturing
cost.
Ceramic knives are made by superplastic forming in Japan.
Examples
Y-TZP @1450℃
Kyocera Ceramic Knife
Superplastic Deformation
Sudhir, Chokshi, J.Am.Ceram.Soc., 2001
Grain boundary sliding
Simulation of Grain Boundary Sliding during deformation
Grain Size 8Y-CSZ
Sintered 2 hours at 1600ºC
0% SiO2, d=10.2µm
1 wt% SiO2, d=2.8µm
3 wt% SiO2, d=1.7µm
5 wt% SiO2, d= 1.6µm 10 wt% SiO2, d=1.2µm
A Superplastic Ceramic
8 mol% Y2O3 Cubic Stabilized ZrO2 + 5 wt.% SiO2
Optimal Microstructure for
Superplasticity
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The smaller the grain size, the easier to achieve
superplastic deformation.
But during high temperature deformation, grains
grow to minimize grain boundary interfacial
area.
Need to design a material in which grain growth
is limited.
How to Create a Stable Fine Grain
Structure at High Temperatures
Grain growth is rapid in single phase materials, slower in two phase materials
(zirconia – silica), but should be very limited in a three-phase microstructure
Two-phase structure
Three-phase structure
II. Experimental Approach
3Al2O3 + 2SiO2 = 3Al2O3•2SiO2
Multiphase ceramic
Alumina – Zirconia – Mullite
ZrO2
(26nm)
Al2O3
(40nm)
SiO2 Sol
(15nm)
Ball Milling
Dry, Sieve and Press
Sintered at 1450℃
Compressive
Deformation
XRD, SEM, TEM
EDS Analysis
Nanocrystalline Ceramic with Alumina, Mullite, Zirconia
SEM of AZ30M30
1E-3
1E-4
1E-5
0
20
40
60
80
True Strain (%)
100
Steady-state deformation of AZ30M30
-1
AZ30M30
AZ15M15
AZ10M10
AZ30
True Strain rate (s )
True Strain Rate (/s)
Deformation Behavior
10
1
10
0
Calculated strain rate
10
-1
10
-2
10
-3
10
-4
10
-5
5.0
-1
0
1 s at 1650 C
5.2 5.4 5.6 5.8 6.0 6.2
Inverse Temperature (10000/T)
High strain rate of AZ30M30
Dislocations generated during deformation
AZ30M30 Deformed Mullite Grain
Conclusions
1. Nanocrystalline/fine grain ceramics may be superior
ionic conductors (increased efficiency for fuel cells).
2. Nanocrystalline/fine grain ceramics have superior
strength at room temperature.
3. Nanocrystalline/fine grain ceramics behave like
metals at high temperatures, but this may be useful
for superplastic forming.
Thanks to the Following for
Research Support
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NSF Division of Materials Research
National Fuel Cell Research Center
NSF REU program
UCI SURP program
UC LEADS program
Pacific Nanotechnology
Corona Naval Base