Co-doping of Lead-free
Bi1/2Na1/2TiO3 (BNT) - Bi1/2K1/2TiO3 (BKT)
-based Piezoceramics
16/10/2014 | TU Darmstadt / Materials Science / Ceramics Group | Martin Blömker | 1
M. Blömker1, E. Erdem2, S. Wollstadt1, J. Rödel1
1: Institute of Materials Science,
Technische Universität Darmstadt, Germany
2: Institut für Physikalische Chemie I
Universität Freiburg, Germany
Why Doping / Co-doping?
16/10/2014 | TU Darmstadt / Materials Science / Ceramics Group | Martin Blömker | 2
Erdem, E. et al., IEEE Trans. Ultras. Ferroel. Freq. Control
55, 1061-1068 (2008)
Cao, W., Disorder and Strain-Induced Complexity in Funct.
Mater. Vol. 148, Ch. 7, 113-134 (Springer Berlin, 2012)
Acceptor doping, e.g.: 𝑀𝑛2𝑂3 → 2𝑀𝑛𝑇𝑖,𝑍𝑟′ + 𝑉𝑂
.. + 3𝑂𝑂𝑋
Donor doping, e.g.: 𝑁𝑏2𝑂5 + 𝑃𝑏𝑂 → 2𝑁𝑏𝑇𝑖,𝑍𝑟. + 𝑉𝑃𝑏
′′
In-
fluen-
ces
Defect dipoles Schottky barriers Domain walls
What are Possible Applications?
16/10/2014 | TU Darmstadt / Materials Science / Ceramics Group | Martin Blömker | 3
Piezoelectric flow meters
Nano-positioning
Energy harvesting
High power applications
Compositions / Synthesis /
XRD Characterization
16/10/2014 | TU Darmstadt / Materials Science / Ceramics Group | Martin Blömker | 4
20 40 60 80
undoped BNKT10
Rietveld refinement
doped BNKT10
222310220
200 211
210111
110
100
rel.
in
ten
sit
y /
a.u
.
degree / 2
56 58 60
undoped BNKT10
Rietveld refinement
doped BNKT10
211
degree / 2
Bi0.5(Na(1-x)Kx)0.5Ti0.995CuyV(0.005-y)O3 , BNKT20 + excess V2O5
Bi0.5(Na(1-x)Kx)0.5Ti1-y(Mn,V,Cu,Mo,Al)y O3
mixing + milling 12h in
ethanol
calcining
800 - 900 °C
milling 12h in
ethanol
uniaxial+
isostatic
at 350 MPa
sintering
1080 - 1150 °C
Solid state sythesis
Less rhombohedral
character upon
(co-)doping
SEM Investigation / Density
16/10/2014 | TU Darmstadt / Materials Science / Ceramics Group | Martin Blömker | 5
BNKT10 undoped More homogeneous size
distribution of doped BNKT10
%TD increases with Cu-content
0 20 40 60 80 100
94
96
98
100
the
ore
tic
al
de
ns
ity
(T
D)
/ %
Cu to V co-dopant ratio
BNKT10:0.3Cu,0.2V
Bi0.5Na0.45K0.05Ti0.995CuyV(0.005-y)O3
5 µm
5 µm
Excess Doping of BNKT20 and
BNKT25 with V2O5
16/10/2014 | TU Darmstadt / Materials Science / Ceramics Group | Martin Blömker | 6
-6 -3 0 3 6
-30
-20
-10
0
10
20
30
po
lari
zati
on
/ µ
C/c
m2
electric field / kV/mm
0.1 wt% V2O5
0.2 wt% V2O5
0.3 wt% V2O5
0.4 wt% V2O5
BNKT25
-6 -3 0 3 6
0.0
0.5
1.0
1.5
2.0
no
rmalized
str
ain
/ ‰
electric field / kV/mm
0.1 wt% V2O5
0.2 wt% V2O5
0.3 wt% V2O5
0.4 wt% V2O5
BNKT25
0 50 100 150 200 250 300 350 400 4500
1000
2000
3000
tan
pe
rmit
tivit
y /
r
T / °C
100 Hz
1 kHz
10 kHz
100 kHz
1 MHz
0
50
100
BNKT25 + 0.2% V2O5
f
f
Pinching of
P-E loop
Strain
increase for
BNKT25
Tf-r lowered
and
broadened
Frequency
dispersion
0.0 0.1 0.2 0.3 0.4
150
200
250
300
BNKT25+xV2O
5
BNKT20+xV2O
5d* 3
3 /
pm
/V
excess V2O
5 / wt.%
16/10/2014 | TU Darmstadt / Materials Science / Ceramics Group | Martin Blömker | 7
-6 -4 -2 0 2 4 6-1.0
-0.5
0.0
0.5
1.0
str
ain
/ ‰
electric field / kV/mm
BNKT10
: 0.5 Cu
: undoped
-6 -4 -2 0 2 4 6
0.0
0.5
1.0
1.5
str
ain
/ ‰
electric field / kV/mm
BNKT20
: 0.5Cu
: undoped
(Co)-doping V + Cu Overview
High strain at MPB + some
tetragonal compositions
(Co)-doping V + Cu Overview
16/10/2014 | TU Darmstadt / Materials Science / Ceramics Group | Martin Blömker | 8
0.4Cu,0.1V fixed,
BKT varied
BKT fixed to 20 %,
Cu to V ratio varied
Tf-r lowered with BKT
content; d*33 rises
d*33 generally higher
due to co-doping
10 20 3040
60
80
100
120
140
160
d*
33
Tf-r
BKT / %
Tf-
r /
°C
0
50
100
150
200
250
300
d* 3
3 /
pm
/V
0 20 40 60 80 10040
60
80
100
120
140
160
pure
BNKT20
Cu to V co-dopant ratio / %
Tf-
r /
°C0
50
100
150
200
250
300
d*
33
Tf-r d
* 33 /
pm
/V
(Co)-doping BNKT10
16/10/2014 | TU Darmstadt / Materials Science / Ceramics Group | Martin Blömker | 9
0 20 40 60 80 1000
10
20
30
Pmax
(6 kV/mm) Pr (6 kV/mm) E
c
V to Cu ratio / %
po
lari
za
tio
n /
µC
/cm
²
4.5
4.8
5.1
5.4
pure
BNKT10
pure
BNKT10
Ec /
kV
/mm
0 50 100 150 200 250 300 350 400 4500
1000
2000
3000
4000
pe
rmit
tiv
ity
( r)
T / °C
100 Hz
1 kHz
10 kHz
100 kHz
1 MHz
0
20
40
60
80
100
BNKT20:0.1V0.4Cu
Ta
n /
%
f
f
BNKT10 based samples →
no bias field
PZT or BT →
bias field upon doping
Hall, D. A. et
al., Journal of
Physics:
Condensed
Matter 10,
9129 (1998).
2000 4000 6000 8000 100000
5000
10000
15000
20000
25000
imp
ed
an
ce (
Z)
/
frequency / kHz
Resonance Measurements
(Co-)doped BNKT10
16/10/2014 | TU Darmstadt / Materials Science / Ceramics Group | Martin Blömker | 10
400 410 420 430 440 4500
2000
4000
6000
imp
ed
an
ce (
Z)
/
frequency / kHz
BNKT10:0.5Cu
2.0 2.5 3.0 3.5
200
400
600
800
1000
1200
imp
ed
an
ce (
Z)
/
frequency / MHz
20 40 60 80 1000.0
0.2
0.4
0.6
0.8
1.0
pure
BNKT10
pure
BNKT10 K
P
QM (P)
co
up
lin
g f
ac
tor
0
20
40
60
80
100
120
QM
20 40 60 80 1000.0
0.2
0.4
0.6
0.8
1.0
Cu to V co-dopant ratio / %
co
up
lin
g f
ac
tor
(th
ick
ne
ss
)0
20
40
60
80
100
120
pure
BNKT10
pure
BNKT10
KT
QM (T)
QM
QM (planar) decreased by Cu
High (up to 0.58) thickness
mode coupling (QM around 5)
b1g
16/10/2014 | TU Darmstadt / Materials Science / Ceramics Group | Martin Blömker | 11
Electron Paramagnetic Resonance
(Co-)doped BNKT10
eg*
t2g
b1g
a1g
b2g
eg
EPR
Oh
octahedral
splitting D4h
Jahn-Teller
splitting
magnetic field
splitting
Elongation X-band EPR
of Cu-doped
BNKT10
Peak
broadening
Cu2+ at
grain
boundaries
/ above
solubility
limit
Electron Paramagnetic Resonance
(Co-)doped BNKT10
16/10/2014 | TU Darmstadt / Materials Science / Ceramics Group | Martin Blömker | 12
𝑉2𝑂5 → 2𝑉𝑇𝑖𝑋
𝐶𝑢𝑂 → 𝐶𝑢′𝑇𝑖′ + 𝑉𝑂
..
𝑉2𝑂5 → 2𝑉𝑇𝑖. + 𝑉𝐵𝑖
′′′ / 𝑉𝑁𝑎,𝐾′
!
V incorporated
as V4+
Cu-V-ratio
influences V-
oxidation state
X-band EPR of sintered samples TiO2
TiO2
TiO2
Summary / Conclusions
16/10/2014 | TU Darmstadt / Materials Science / Ceramics Group | Martin Blömker | 13
Co-doping at rhombohedral site of MPB (BNKT10)
Butterfly-type strain curve, high KT, Pr, Pmax, Ec and Tf-r
Transducers, high power applications
Co-doping at MPB (BNKT20) / excess doping
Polarization loop pinching, high Smax, low Ec, relatively low Tf-r
Actuator applications
Vanadium state V5+? / V4+; Cu2+ at grain boundaries
Thank you
for your attention!
16/10/2014 | TU Darmstadt / Materials Science / Ceramics Group | Martin Blömker | 14
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