Developing Lead-Free
Piezoceramics
Jürgen Rödel
Institute of Materials Science
Technische Universität Darmstadt
Germany
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 1
Outline
I.
Introduction Ferroelectrics Division (2)
Projects and Teams
II.
Lead-Free Piezoceramics (3)
Legislation and History
III. BNT-Based Relaxors (13)
Structure and Electrical Properties
IV. BCT-BZT Based Ceramics (7)
Room Temperature Applications
V.
KNN-Based Ceramics (4)
Temperature Stability
VI. Transfer (3)
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 2
Ferroelectrics: starting projects – 2003
5 projects ended
Synthesis
A1
Rödel
Lead-Free
Modeling
Characterization
A2
Hoffmann
PZT
B1
Eichel/Dinse
B3
Kleebe/Donner
TEM/XRD
ended 2010
ended 2010
B5
Lupascu/Rödel
C1
Albe
Defect Structure
C3
Müller/Becker
ended 2010
B2
Balogh
ended 2010
ended 2006
B7
von Seggern/Klein
Polarization Dynamics
Components
C5
Genenko/von Seggern
Charge Transport
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 3
D1
Rödel
El. Fatigue
Ferroelectrics: current projects – 2014
4 new projects started
Characterization
Synthesis
B9
Buntkowsky
NMR
A1
Rödel
Lead-Free
Modeling
C6
Xu
defect /dw
interaction
started 2009
C1
Albe
Defect Structure
Components
started 2012
C5
Genenko/von Seggern
Charge Transport
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 4
D6
Webber
Mechanics
started 2012
B3
Kleebe/Donner
TEM/XRD
B7
von Seggern/Klein
Polarization Dynamics
T2
Hoffmann
PbO Stoichiometry
started 2011
D1
Rödel
El. Fatigue
Legislation
RoHS II
ELV
Lead-containing piezoelectric devices
Lead-containing piezoelectric devices
Category 7
Category 10 (a)
Exemptions expire latest after maximum validity period
5 years (July 2016)
Categories 1-7,10
Continuous process
UNLESS INDUSTRY REQUESTS CONTINUATION!
18 MONTHS PRIOR TO EXPIRY  Next revision for INDUSTRY July 2016
EU-Directive 2000/53/EC: ELV. Off. J. Eur. Un. 2000;L 269:34 // EU-Directive 2011/65/EU: RoHS II. Off. J. Eur. Un. 2011;L 174:88
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 5
History of lead-free piezoceramics
KNN-based
Other
BNT-based
1954 1st report KNN (Shirane et al.)
1959 Piezoelectric data of KNN
1957 BKT discovery (Popper et al.)
1960 BKT properties
(Egerton&Dillon)
(Smolenskii et al.)
1945 BaTiO3
piezo transducer
1945 Poling
process
(patent)
(Gray)
mid 1950s PZT ceramics
1991 BNT-BT (Takenaka et al.)
2004 LF4
composition
(Saito et al.)
2004 Improving
the sintering,
e.g. Cu-doping
1996 BNT-BKT (Elkechai et al.)
2001 EU LEAF project
2007 BNT-BT-KNN (Zhang et al.)
2003 1st EU legislative
2009 hard BNT-BT for ultrasonic
cleaners (Tou et al.)
2009 BCT-BZT (Liu, Ren)
2014 Mn- and Fe-doped BNTBKT-BLT (Taghaddos et al.)
2014 BCT-BZT high d33*
(Matsubara et al.)
2013 Temperature-insensitive
strain in KNN
(Wang et al.)
2014 KNN+ Ni electrodes
(Liu et al.)
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 6
(Ehmke et al.)
Publications on lead-free piezoceramics
454
Warwick
9
287
Darmstadt
Karlsruhe
Lausanne
Bordeaux
5
Anzahl
Veröffentlichungen
0
2013
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 7
4 29
Ljubljana
200
Zitierungen in
2013 (von
Veröffentlichungen
0
aus 2009-2013)
BNT-based
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 8
BNT-based piezoceramics - projects
length scale
macroscopic
atomic
A1
Rödel
Synthesis
D1
Rödel
Electrical
Fatigue
B3
Kleebe/Donner
TEM/XRD
D6
Webber
Mechanics
C5
Genenko/von Seggern
Charge Transport
B7
von Seggern/Klein
Polarization Dynamics
B9
Buntkowsky
NMR
experiment
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 9
C6
Xu
Defect/DW
Interaction
C1
Albe
Defect Structure
theory
P(E,T) in BNT-6BT
Ferroelectric
Nonergodic
Long-range
Relaxor
order
E
TF-R
P
E
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 10
D1
Ergodic
Relaxor
E-T Diagram in BNT-3BT:Mn
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 11
D1
Sapper et al., J. Appl. Phys. 115, 194104 (2014)
Fe-modification=hard-doping?
expectation:
Ebias up
Pr down
strongly aged:
pinched loop
measurement
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 12
D1
MAS NMR –
Local structure of BNT-6BT
23Na
unpoled
mixture
ST
< 1.5
CT
B9
poled
non-cubic
CT
ST
= 1.5
CT
200000
ST
Intensity (arb. unit)
200000
ST
= 1.07
CT
100000
CT
100000
3000
2000
1000
0
3000
2000
1000
0
500 250
0 -250 -500
-L (kHz)
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 13
500 250
Intensity (arb. unit)
ST
= 1.42
0 -250 -500
-L (kHz)
Pedro Braga-Groszewicz, submitted to PRL
Atomic Structure of BNT
C1
• Zero pressure: BNT is structurally frustrated
• Ab initio calculations suggest the existence of
chemically ordered nanoregions (CNR)
• Matrix: R3c-like CNR: Pbnm-like
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 14
Gröting et al., Phys. Rev. B. 86, 134118 (2012)
Diffuse scattering BNT-4BT single crystal
B3
Defect:
Stacking Fault
in Tilt Sequence
Streaks
→ Random Stacking Faults
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 15
Stacking Faults are the
Boundaries of PNRs
Streaks: Daniels et al., Appl. Phys. Lett. 98, 252904 (2011)
TEM as f(T) in BNT-6BT-1KNN
A1, B3
94BNT-5BT-1KNN
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 16
Kling et al., J. Am. Ceram. Soc. 96, 3312 (2013)
Phase transitions in BNT-6BT: f(σ)
A1,(D6)
• Stress-free XRD:
polar tetragonal P4mm to non-polar
tetragonal P4/mmm at 195°C
no remanent strain
P4/bm
P4/mmm
• Uniaxial compressive stress:
Field-induced P4/mmm to P4/bm
→oxygen octahedral tilting
→stress induced phase transition
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 17
Webber et al., J. Appl. Phys. 108, 014101 (2010)
BNT-based actuator materials
0.5
BNT-6BT-2KNN
textured KNN (LF4T)
S (%)
0.4
soft PZT
0.3
BNT-28ST
BNT-18BT-12KNN
0.2
0.1
BNBK2:1 MPB
0.0
0
2
4
6
8
E (kV/mm)
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 18
Jo et al., J. Electroceram. 29, 71-93 (2012)
Relaxor Ferroelectric Composites
A1, C. Groh
associated
S
matrix
Susa Susa
composite
Epol
E
Epol
Mechanism:
• Electric field  seed gets poled first  propagates polarization to matrix 
core gets “easier” poled ≙ polarization at lower fields (Epol )
• Only small amounts of shell required (nuclei of polarization)  maintain the
high strain of matrix
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 19
Groh et al., Adv. Funct. Mat. 24, 336-362 (2014)
A1, C. Groh
Haibo Zhang (AvH)
Coupling mechanisms
Polarization coupling
700
700
Emax=6 kV/mm
600
500
400
300
200
100
Emax=6 kV/mm
600
Emax=4 kV/mm
d33*(pm/V)
d33*(pm/V)
Strain coupling
Emax=4 kV/mm
500
400
300
200
0
20
40
60
80
FE content (vol.%)
100
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 20
100
0
20
40
60
80
FE content (vol.%)
100
BZT-BCT
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 21
Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3
100
90
T (°C)
80
A1, M. Acosta
associated
Extrapolation x=0.36 to 0.5
TR-O
TO-T
C
Tc
70
T
60
50
40
R
O
30
0.30 0.35 0.40 0.45 0.50 0.55 0.60
BZT-xBCT
Acosta et al., Acta Mater. 80, 48-55 (2014)
• Qualitative agreement in phase diagram
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 22
Keeble et al., Appl. Phys. Lett. 102, 092903 (2013)
BZT-xBCT: small signal d33 as f(x, T)
d33 (pC/N)
C
A1, M. Acosta
associated
T
R
•
•
•
O
Peak at O-T phase transition
No peaking at triple points
Applications limited below 95 °C at x=0.6  d33~300 pC/N
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 23
Acosta et al., Acta Mater. 80, 48-55 (2014)
BZT-xBCT: large signal d33* as f(x, T)
A1, M. Acosta
associated
O
•
•
•
Peak at R-O and O-T phase transitions
No peaking at convergence region!
Low temperature stability limits applications below 90 °C
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 24
Acosta et al., Acta Mater. 80, 48-55 (2014)
In-situ E-field studies
BZT-0.32BCT
virgin
A1, M. Acosta, B3
X. Tan (Iowa State Univ., USA)
1.48 kV/cm
2 kV/cm
virgin
2 kV/cm
3.2 kV/cm
4.2 kV/cm
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 25
5 kV/cm
H.Guo, X.Tan, Iowa State University, USA
2
Polarization (C/m )
Polarization dynamics in BZT-xBCT
A1, M. Acosta
B7, S. Zhukov
Thermodynamic
activation barrier
per unit of volume
0.20
0.15
0.10
0.05
0.00
-0.05
-0.10
-0.15
-0.20
Critical volume of
nucleating domain
x=0.35
-3
-2
x=0.45
-1 0 1
E(kV/mm)
x=0.6
2
3
Activation barrier
• Maximized properties due to minimum
in activation barrier for domain
switching
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 26
Zhukov et al. Appl. Phys. Lett. 103, 152904 (2013)
BZT-BCT under
uniaxial compressive stress
A1, M. Ehmke
Purdue Univ., USA
BNT-40BCT
•
Stress < 50 MPa increasing d33* at low E and T
•
Mechanical loading: E stabilizes domains parallel to stress
•
Moderate stresses: favour strain
→ E is large enough to reorient ferroelastically switched domains
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 27
M. Ehmke et al., Acta Mater. 78, 37-45 (2014)
KNN-based
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 28
@4kV/mm
o
30
o
C
o
Ke Wang (AvH fellow)
Tsinghua Univ., China
0.08
0.04
0.00
-1
E (kVmm / scale)
S=Q(Pmax2-Pr2)
300pm/V < d33* < 350pm/V
from RT to 175°C
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 29
Piezoelectric constant (pm/V)
20
0
Strain (%)
0.12
22
C
0.16
C
35 o
C
40 o
C
50 o
80 o C
C
10
0o
C
12
5o
15 C
0o
17 C
5o
C
Temperature-Insensitive Strain
in modified KNN
400
(Li, Ta)-KNN-CaZrO3
300
200
small signal d33
100
large signal d*33
0
50
100
150
200
o
Temperature ( C)
Ke Wang et al., Adv. Funct. Mater. 23, 4079-86 (2013)
300
Aim: phase boundary between
tetragonal and rhombohedral
200
(1-x)(Na0.5K0.5)NbO3–xBaZrO3
• rhombohedral 0.08 ≤ x ≤ 0.15
(RT)
100
500
3000
R
T
60
50
(RT)
2000
1000
d33(pC/N)
400
40
300
30
200
20
100
0
(1-x)(Na0.5K0.5)NbO3–
x(Bi0.5Li0.5)TiO3
• tetragonal 0.06 ≤ x ≤ 0.15
(RT)
kp(%)
t (oC)
MPB in KNN-based ceramics
Ruiping Wang
(AIST, Tsukuba, Japan)
10
0
0
0
0.02
0.04
x
0.06
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 30
0.90(Na0.5K0.5)NbO3–xBaZrO3
–(0.10-x)(Bi0.5Li0.5)TiO3
0.08
J. Zushi, R. Wang et al., Jpn .J. Appl. Phys., 52 (2013)
d33(T) in KNN-based MPB material
Ruiping Wang
(AIST, Tsukuba, Japan)
Piezoelectric constant (pm/V)
MPB composition 9262BBL
700
d
600
33
at 10 Hz
small signal d
500
33
large signal d*
33
400
@2kV/mm
300
200
0.92(Na0.5K0.5)NbO3xBaZrO3(0.08-x)(Bi0.5Li0.5)TiO3
100
0
0
50
100 150 200
o
Temperature ( C)
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 31
250
300
R. Wang et al., unpublished
Summary:
Innovation management
Legislation trigger
Peak of inflated expectations
Trough of disillusionment
Transfer enlightenment
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 32
Worldwide Research Trend
Publications/Expectations
Pick low-hanging fruits
Low-hanging fruits picked
Deeper Science
(Adv. Fun. Mat, APL)
Application Relevance
EU-Legislative
Nature Paper Saito
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 33
Industrial Development
year
2000
2010
2020
2030
Publications/Expectations
High Frequency and
Sensing Applications
• High Power
• Ultrasonic Cleaner
• Knocking Sensor
• Parking Pilot
• Flow Meter
High Reliability
• Fuel Injector
-20
-10
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 34
0
year
10
20
Acknowledgements
TU Darmstadt:
W. Jo, R. Dittmer, S. Schaab, T. Granzow, J. Glaum, E. Anton, E. Sapper, S. Zhang, J. Chen, E. Aulbach, D.
Isaia, C. Groh, M. Acosta, J. Zang, H. Zhang, J. Kling, L. Schmitt, M. Hinterstein, A. Kleebe, W. Donner, H.
v.Seggern, G. Buntkowsky, P. Braga-Groszewicz, K. Webber. S. Zhukov
Ferroelectrics:
D. Damjanovic (EPFL, Switzerland) X. Tan (Iowa State University, USA (TEM)
BNT-based relaxors:
A.J. Bell (Leeds University, UK) ; J.-S. Lee (Ulsan University, Korea) ; S.J. Jeong (KERI, Korea)
KNN:
K. Wang, J.F. Li (Tsinghua University, Beijing, CH) ; R. Wang, (AIST, Tsukuba, Japan)
BCT-BZT:
M. Ehmke, J. Blendell, (Purdue, USA), K.J. Bowman, (IIT, USA)
Single crystals (BNT-BT):
D. Rytz (FEE, Germany)
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 35

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