Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 1
Developing Lead-Free
Piezoceramics
Jürgen Rödel
Institute of Materials Science
Technische Universität Darmstadt
Germany
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 2
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 | 3
Ferroelectrics: starting projects – 2003 5 projects ended
B3
Kleebe/Donner
TEM/XRD A1
Rödel
Lead-Free
B7
von Seggern/Klein
Polarization Dynamics
C1
Albe
Defect Structure
C5
Genenko/von Seggern
Charge Transport
D1
Rödel
El. Fatigue
Synthesis Characterization
Modeling
Components
A2
Hoffmann
PZT ended 2010
B1
Eichel/Dinse ended 2010
B2
Balogh ended 2010
B5
Lupascu/Rödel ended 2006
C3
Müller/Becker ended 2010
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 4
Ferroelectrics: current projects – 2014 4 new projects started
B3
Kleebe/Donner
TEM/XRD A1
Rödel
Lead-Free B7
von Seggern/Klein
Polarization Dynamics C1
Albe
Defect Structure
C5
Genenko/von Seggern
Charge Transport
D1
Rödel
El. Fatigue
Synthesis Characterization
Modeling
Components C6
Xu
defect /dw
interaction started 2012
B9
Buntkowsky
NMR started 2009
D6
Webber
Mechanics
started 2012
T2
Hoffmann
PbO Stoichiometry started 2011
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 5
Legislation
ELV
Lead-containing piezoelectric devices
Category 10 (a)
RoHS II
Lead-containing piezoelectric devices
Category 7
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 2011/65/EU: RoHS II. Off. J. Eur. Un. 2011;L 174:88 EU-Directive 2000/53/EC: ELV. Off. J. Eur. Un. 2000;L 269:34 //
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 6
History of lead-free piezoceramics
1945 BaTiO3
piezo transducer (patent)
mid 1950s PZT ceramics
1945 Poling
process (Gray)
1954 1st report KNN (Shirane et al.)
1959 Piezoelectric data of KNN (Egerton&Dillon)
2004 LF4
composition (Saito et al.)
2004 Improving
the sintering,
e.g. Cu-doping (Matsubara et al.)
2001 EU LEAF project
2003 1st EU legislative
1957 BKT discovery (Popper et al.)
1960 BKT properties (Smolenskii et al.)
1991 BNT-BT (Takenaka et al.)
2007 BNT-BT-KNN (Zhang et al.)
KNN-based BNT-based Other
2009 BCT-BZT (Liu, Ren)
2014 KNN+ Ni electrodes (Liu et al.)
2013 Temperature-insensitive
strain in KNN (Wang et al.)
1996 BNT-BKT (Elkechai et al.)
2009 hard BNT-BT for ultrasonic
cleaners (Tou et al.)
2014 Mn- and Fe-doped BNT-
BKT-BLT (Taghaddos et al.)
2014 BCT-BZT high d33* (Ehmke et al.)
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 7
Publications on lead-free piezoceramics
Warwick
Zitierungen in
2013 (von
Veröffentlichungen
aus 2009-2013) 0
200 Anzahl
Veröffentlichungen
2013
5
0
Bordeaux Lausanne
Darmstadt
Ljubljana
29
9
287
454
Karlsruhe
4
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 8
BNT-based
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 9
BNT-based piezoceramics - projects
A1
Rödel
Synthesis
B3
Kleebe/Donner
TEM/XRD
B7
von Seggern/Klein
Polarization Dynamics
B9
Buntkowsky
NMR
C1
Albe
Defect Structure
C5
Genenko/von Seggern
Charge Transport
C6
Xu
Defect/DW
Interaction
D1
Rödel
Electrical
Fatigue
D6
Webber
Mechanics
atomic
macro-
scopic
length
scale
experiment theory
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 10
P(E,T) in BNT-6BT
Ergodic
Relaxor
Nonergodic
Relaxor
Ferroelectric
Long-range
order
TF-R
E
P
E
D1
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 11
E-T Diagram in BNT-3BT:Mn D1
Sapper et al., J. Appl. Phys. 115, 194104 (2014)
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 12
Fe-modification=hard-doping? D1
expectation:
Ebias up
Pr down
strongly aged:
pinched loop
measurement
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 13
23Na MAS NMR –
Local structure of BNT-6BT B9
Pedro Braga-Groszewicz, submitted to PRL
500 250 0 -250 -5000
1000
2000
3000
100000
200000
500 250 0 -250 -5000
1000
2000
3000
100000
200000
Inte
nsity (
arb
. u
nit)
-L (kHz)
Inte
nsity (
arb
. u
nit)
-L (kHz)
CT
ST
Unpoled Poled
Cubic 25.9% 2.1%
Polar 74.1% 97.9%
unpoled
ST
CT= 1.07
ST
CT= 1.5
poled
ST
CT< 1.5
ST
CT= 1.42
non-cubic mixture
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 14
Atomic Structure of BNT C1
Gröting et al., Phys. Rev. B. 86, 134118 (2012)
• 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 | 15
Diffuse scattering BNT-4BT single crystal B3
Streaks
→ Random Stacking Faults
Defect:
Stacking Fault
in Tilt Sequence
Stacking Faults are the
Boundaries of PNRs
Streaks: Daniels et al., Appl. Phys. Lett. 98, 252904 (2011)
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 16
TEM as f(T) in BNT-6BT-1KNN
Kling et al., J. Am. Ceram. Soc. 96, 3312 (2013)
A1, B3
94BNT-5BT-1KNN
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 17
Phase transitions in BNT-6BT: f(σ) A1,(D6)
Webber et al., J. Appl. Phys. 108, 014101 (2010)
• Stress-free XRD:
polar tetragonal P4mm to non-polar
tetragonal P4/mmm at 195°C
• Uniaxial compressive stress:
Field-induced P4/mmm to P4/bm
→oxygen octahedral tilting
→stress induced phase transition
no remanent strain
P4/mmm
P4/bm
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 18
BNT-based actuator materials
0 2 4 6 80.0
0.1
0.2
0.3
0.4
0.5
BNBK2:1 MPB
textured KNN (LF4T)
soft PZT
BNT-6BT-2KNN
S (
%)
E (kV/mm)
BNT-18BT-12KNN
BNT-28ST
Jo et al., J. Electroceram. 29, 71-93 (2012)
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 19
Relaxor Ferroelectric Composites
matrix
S
E
Susa
Epol
composite
Susa
Epol
• 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
Mechanism:
A1, C. Groh
associated
Groh et al., Adv. Funct. Mat. 24, 336-362 (2014)
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 20
-6 -4 -2 0 2 4 6
-0.4
-0.2
0.0
0.2
0.4
Pola
rizatio
n (
C/m
2)
Electric field (kV/mm)
RE
FE
@0.05 Hz
0 1 2 3 4 5 60.0
0.1
0.2
0.3
0.4
0.5
FE
FE: Epol
=1.9 kV/mm
RE: Epol
=4.6 kV/mm
Str
ain
(%
)
Electric field (kV/mm)
RE
@0.05Hz
Polarization coupling Strain coupling
Coupling mechanisms
0 20 40 60 80 100100
200
300
400
500
600
700 E
max=6 kV/mm
Emax
=4 kV/mm
d33*(
pm
/V)
FE content (vol.%)0 20 40 60 80 100
100
200
300
400
500
600
700 E
max=6 kV/mm
Emax
=4 kV/mm
d33*(
pm
/V)
FE content (vol.%)
A1, C. Groh
Haibo Zhang (AvH)
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 21
BZT-BCT
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 22
Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3
Keeble et al., Appl. Phys. Lett. 102, 092903 (2013)
• Qualitative agreement in phase diagram Acosta et al., Acta Mater. 80, 48-55 (2014)
0.30 0.35 0.40 0.45 0.50 0.55 0.60
30
40
50
60
70
80
90
100
T
OR
T (
°C)
BZT-xBCT
C
Extrapolation x=0.36 to 0.5
TR-O
TO-T
Tc
A1, M. Acosta
associated
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 23
BZT-xBCT: small signal d33 as f(x, T)
d33 (pC/N)
• Peak at O-T phase transition
• No peaking at triple points
• Applications limited below 95 °C at x=0.6 d33~300 pC/N
A1, M. Acosta
associated
R O
T
C
Acosta et al., Acta Mater. 80, 48-55 (2014)
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 24
BZT-xBCT: large signal d33* as f(x, T)
• Peak at R-O and O-T phase transitions
• No peaking at convergence region!
• Low temperature stability limits applications below 90 °C
A1, M. Acosta
associated
Acosta et al., Acta Mater. 80, 48-55 (2014)
O
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 25
In-situ E-field studies
BZT-0.32BCT
3.2 kV/cm 4.2 kV/cm 5 kV/cm
virgin
2 kV/cm
2 kV/cm virgin 1.48 kV/cm
H.Guo, X.Tan, Iowa State University, USA
A1, M. Acosta, B3
X. Tan (Iowa State Univ., USA)
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 26
Polarization dynamics in BZT-xBCT
Thermodynamic
activation barrier
per unit of volume
Critical volume of
nucleating domain
Activation barrier
Zhukov et al. Appl. Phys. Lett. 103, 152904 (2013)
• Maximized properties due to minimum
in activation barrier for domain
switching
A1, M. Acosta
B7, S. Zhukov
-3 -2 -1 0 1 2 3
-0.20
-0.15
-0.10
-0.05
0.00
0.05
0.10
0.15
0.20
x=0.35
Pola
rization (
C/m
2)
E(kV/mm)
x=0.45 x=0.6
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 27
BZT-BCT under
uniaxial compressive stress
M. Ehmke et al., Acta Mater. 78, 37-45 (2014)
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
A1, M. Ehmke
Purdue Univ., USA
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 28
KNN-based
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 29
Temperature-Insensitive Strain
in modified KNN
0.00
0.04
0.08
0.12
0.16
200o C
175o C
150o C
125o C
100o C
80o C50
o C
40o C
35o C
30o C
Str
ain
(%
)
E (kVmm-1 / scale)
22o C
@4kV/mm
(Li, Ta)-KNN-CaZrO3
S=Q(Pmax2-Pr
2)
300pm/V < d33* < 350pm/V
from RT to 175°C 50 100 150 200
0
100
200
300
400
small signal d33
large signal d*33
Pie
zoele
ctric
const
ant
(pm
/V)
Temperature (oC)
Ke Wang et al., Adv. Funct. Mater. 23, 4079-86 (2013)
Ke Wang (AvH fellow)
Tsinghua Univ., China
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 30
MPB in KNN-based ceramics
0
100
200
300
400
500
0
10
20
30
40
50
60
0 0.02 0.04 0.06 0.08
d33(p
C/N
)
k p(%
)
x
0
1000
2000
3000
(R
T)
100
200
300
t (o
C)
R T
J. Zushi, R. Wang et al., Jpn .J. Appl. Phys., 52 (2013)
0.90(Na0.5K0.5)NbO3–xBaZrO3
–(0.10-x)(Bi0.5Li0.5)TiO3
Aim: phase boundary between
tetragonal and rhombohedral
(1-x)(Na0.5K0.5)NbO3–xBaZrO3
• rhombohedral 0.08 ≤ x ≤ 0.15
(RT)
(1-x)(Na0.5K0.5)NbO3–
x(Bi0.5Li0.5)TiO3
• tetragonal 0.06 ≤ x ≤ 0.15
(RT)
Ruiping Wang
(AIST, Tsukuba, Japan)
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 31
d33(T) in KNN-based MPB material
0
100
200
300
400
500
600
700
0 50 100 150 200 250 300
d33
at 10 Hz
small signal d33
large signal d*33
Pie
zoele
ctr
ic c
onsta
nt
(pm
/V)
Temperature (oC)
@2kV/mm
MPB composition 9262BBL
R. Wang et al., unpublished
Ruiping Wang
(AIST, Tsukuba, Japan)
0.92(Na0.5K0.5)NbO3-
xBaZrO3-
(0.08-x)(Bi0.5Li0.5)TiO3
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 32
Summary:
Innovation management
Legislation trigger
Peak of inflated expectations
Trough of disillusionment
Transfer enlightenment
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 33
Worldwide Research Trend
Nature Paper Saito EU-Legislative
Public
ations/E
xpecta
tions
Nature Paper Saito EU-Legislative
Public
ations/E
xpecta
tions
Nature Paper Saito EU-Legislative
Pick low-hanging fruits Low-hanging fruits picked
Public
ations/E
xpecta
tions
Deeper Science
(Adv. Fun. Mat, APL)
Application Relevance
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 34
Industrial Development
Public
ations/E
xpecta
tions
0 -20 20 10 -10
2010 2020 2030 2000 year
year
High Frequency and
Sensing Applications
• High Power
• Ultrasonic Cleaner
• Knocking Sensor
• Parking Pilot
• Flow Meter
High Reliability
• Fuel Injector
Jürgen Rödel | TU Darmstadt | Materials Science – Ceramics Group | 35
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)
Acknowledgements