Types of Ferroelectric Materials

1
Types of Ferroelectric Materials

• Ferroelectric Materials can be structurally
  categorized into 4 groups
• Corner Sharing Octahedra
• 1.1 Perovskite-Type Compounds
• (such as BaTiO3, PT, PZT, PMN, and PLZT)
• 1.2 Lithium Niobate and Tantalate
• (such as LiNbO3 and LiTaO3)
• 1.3 Bismuth Oxide Layer Structured Compounds
• (such as Bi4Ti3O12 and PbBi2Nb2O9)
• 1.4 Tungsten-Bronze-Type Compounds
• (such as PbNb2O6)
• Compounds Containing Hydrogen Bonded Radicals
• (such as KDP, TGS, and Rochelle Salt)
• Organic Polymers (such as PVDF and co-polymers)
• Ceramic Polymer Composites (such as PZT-PE)

Done
2
LiNbO3 and LiTaO3 Single Crystals

• ! Important ferroelectric crystals !
• (FE discovered in 1949)
• Large crystals grown by Czochralskis technique
• Excellent piezoelectric, pyroelectric, optical
  and electro-optics properties
• Very stable with very high Tc (1210 C for LiNbO3
  and 620 C for LiTaO3 )
• Chemically stable and insoluble in water and
  organic solvents
• Mostly used in crystal form (partly due to
  limited piezoelectric activity in ceramic form)
• High mechanical Qm and low acoustic losses
• Good high frequency transducers and surface
  acoustic wave devices
• Good high temperature transducers
• Infrared detectors (due to LiTaO3s good
  pyroelectricity)
• Laser modulator, frequency multiplier, wave
  generator (as a result of their good optic and
  electro-optic properties

3
LiNbO3 and LiTaO3 Single Crystals

• Restricted Perovskite
• Structures of LiNbO3 and LiTaO3 are similar (but
  not identical) to Ilminite (FeTiO3) ? Connected
  Distorted Oxygen Octahedra ? Neighboring
  octahedra connected through a common tie-end
  oxygen ion (corner-sharing of MO6 (M Nb or Ta))
  ? Share one face with LiO6 ? Share opposite
  face with empty O6 octahedral ? Sequence Nb (or
  Ta), vacancy, Li, Nb (or Ta), vacancy, Li, ......

4
LiNbO3 and LiTaO3 Single Crystals

• Ferroelectric-Paraelectric Phase Transition
• Second-order or very close to second-order
  phase transition
• ?
• Ps along c-axis (ions displacement direction) and
  only 180 domains
• (hard to get substantial piezoelectricity in
  ceramics)
• ?
• Nb5 moves to center of the oxygen octahedral
• Li moves towards the nearest oxygen plane
• ?
• Nb5 at the median between the nearest oxygen
  planes (Ps 0)
• ?
• Trigonal (or Hexagonal) structure with 3m
  ferroelectric phase

5
LiNbO3 and LiTaO3 Single Crystals
Orientation Dependence of electromechanical
coupling factor k31 of LiNbO3

• Piezoelectric Applications
• Anisotropic Properties Directional Dependent
  Properties
• ?
• High coupling (0.50) and low-temperature
  dependence of resonant frequency
• (higher than quartz)
• ZYw (20-50)-cut
• High Qm
• ?
• Suitable high-frequency filter applications

6
LiNbO3 and LiTaO3 Single Crystals
Orientations for LiNbO3 crystal plates for
ultrasonic transducers

• High Frequency Ultrasonic Transducer
  Applications
• Four cut-types for different applications (up to
  several hundred GHz)
• ?
• Z-cut for thickness-extension vibrational mode
  (low kt 0.17)
• 35 Y-cut for another thickness-extension
  vibrational mode
• 163 Y-cut for strong thickness-sheer mode
• X-cut for strong thickness-sheer mode with high
  effective coupling factor of 0.68
• Other Piezoelectric Applications
• ?Ultrasonic Wave Propagator (due to low acoustic
  loss) ?
• ? Microwave Acoustic Amplifier ?

7
LiNbO3 and LiTaO3 Single Crystals

• Pyroelectric Applications
• High Curie temperature, substantial pyroelectric
  coefficient, chemical and physical stability, and
  lower dielectric constant
• ?
• Materials for Infrared Detectors
• Electro-optic Applications
• Most important applications
• Good linear electro-optical effect
• Photoelastic effect
• Non-linear optical effect
• Large-sized and optical quality crystals
• ?
• Electro-Optical (EO) Modulation Devices
• linear EO modulator
• traveling-wave modulator
• wave-guide modulator
• EO Q-switch
• Optical Frequency Doubler

8
Bismuth Oxide Layer Structure Ferroelectrics
Bi4Ti3O12 and Pb(Bi2Nb2O9) ? Corner-linked
perovskite-like sheets separated by (Bi2O2)2
layers with perovskite-like unit (1, 2, 3, or
more units) ? General Formula (Bi2O2)2(Am-1BmO3m
1)2- A Bi, Pb, Ba, Sr, Ca, Na, K B Ti, Nb,
Ta, W, Mo, Fe, Co, Cr ? Ferroelectric at room
temperature Melting point above 1100 C Curie
Temperature 300-700 C Bi4Ti3O12 ? Tc 675 C T
lt Tc FE Monoclinic (Pseudo-Orthorhombic) T gt Tc
PE Tetragonal
9
Bismuth Oxide Layer Structure Ferroelectrics
Alternating Layer Structures of Oxygen
Octahedra A ? a layer composed of
(Bi2Ti3O10)2- B ? a unit of an imaginary
perovskite structure of BiTiO3 C ? a layer of
(Bi2O2)2
10
Bismuth Oxide Layer Structure Ferroelectrics
Bi4Ti3O12 and Pb(Bi2Nb2O9) ? Plate-like crystal
structure ? Highly anisotropic FE
properties ? Ceramics do not have very good
piezoelectric properties (as a result of low
poling efficiency and high coercive field)
? Improved by grain-orientation during
processing (tape-casting and hot-forged
sintering Important Piezoelectric
Ceramics ? Higher stability Higher operating
temperature (High Tc) Higher operating
frequency ? Piezoelectric Resonator Ferroelectric
Optical Memory Devices (Bi4Ti3O12 crystals)
11
Tungsten-Bronze-Type Ferroelectrics
Projection of the Tungsten-Bronze Structure on
the (001) plane (Orthorhombic and Tetragonal
Cells are shown in solid and dotted lines)
Tetragonal Tungsten Bronze KxWO3
(xlt1) ? (A1)2(A2)4(C)4(B1)2(B2)8O30 A1, A2, C,
B1, B2 are partially or fully occupied
12
Tungsten-Bronze-Type Ferroelectrics
Tetragonal Tungsten Bronze (A1)2(A2)4(C)4(B1)2(
B2)8O30 A1, A2, C, B1, B2 partially or fully
occupied ? IF one in six of A1 and A2 is
vacant ? AB2O6 ? 5 Pb2 ions in A1 and A2 10 Nb5
ions in B1 and B2 ? PbNb2O6 Lead Niobate ? First
Non-Perovskite Oxide-Type Ferroelectric Discovered
Structure with Open Nature ? Wide range of
cation and anion substitutions without loss of
ferroelectricity ? More than 85
Tungsten-Bronze-Type ferroelectrics
13
Tungsten-Bronze-Type Ferroelectrics
Lead Niobate (PbNb2O6) ? High Tc 560 C, Large
d33/d31, Large dh (dh d332d31), and Low
mechanical Q ? Broad-band, high-temperature,
transducer applications ? Processing
difficulties hard to obtain ceramics with lt 7
porosity a stable non-ferroelectric
rhombohedral phase formed large volume change
from phase trnasformation during cooling leads to
cracks Other Alkali/Alkali-Earth Niobate
Materials PbTa2O6, BaNb2O6, SrNb2O6, Pb½Ba½Nb2O6,
Sr½Ba½Nb2O6 ? Potential Applications ?laser
modulation ? ? pyroelectric detectors ? ?
hydrophones ? ? ultrasonic applications ?
14
Some Other Corner-Sharing Octahedra Ferroelectrics
CaZrO3, SrZrO3, SrTiO3, CaTiO3, PbHfO3, KNbO3,
NaNbO3, AgNbO3, KTaO3, NaTaO3, AgTaO3, RbTaO3,
KTa1-xNbxO3 (KTN), BiFeO3, WO3 and their
solid-solutions PbTa2O6, SrTa2O7, Cd2Nb2O7,
KSr2Nb5O15, Ba2NaNb5O15, Sr4KLiNb10O30 (K,Na)(Sr
,Ba)Nb2O6 (KNSBN) and their solid
solutions NaVO3, AgVO3, BaAl2O4 !! This is jut
a small portion of an endless list of
ferroelectric materials!!
15
Types of Ferroelectric Materials

• Ferroelectric Materials can be structurally
  categorized into 4 groups
• Corner Sharing Octahedra
• 1.1 Perovskite-Type Compounds
• (such as BaTiO3, PT, PZT, PMN, and PLZT)
• 1.2 Lithium Niobate and Tantalate
• (such as LiNbO3 and LiTaO3)
• 1.3 Bismuth Oxide Layer Structured Compounds
• (such as Bi4Ti3O12 and PbBi2Nb2O9)
• 1.4 Tungsten-Bronze-Type Compounds
• (such as PbNb2O6)
• Compounds Containing Hydrogen Bonded Radicals
• (such as Rochelle Salt, KDP, and TGS)
• Organic Polymers (such as PVDF and co-polymers)
• Ceramic Polymer Composites (such as PZT-PE)

Done
16
Ferroelectrics with Hydrogen Bonded Radicals
KDP, TGS, and Rochelle Salt ? Still being used in
some applications ? Superior in some features and
properties ? Large crystals with optical quality
easily grown from aqueous solution Rochelle salt
has very good piezoelectric properties KDP family
has good electro-optic and non-linear optic
properties TGS family has very excellent
pyroelectric properties ? Disadvantages ? Reason
ably weak ferroelectricity, low Tc, poor
mechanical properties. and water
soluble ? Gradually being replaced by
piezoelectric ceramics and crystals
17
Ferroelectrics with Hydrogen Bonded Radicals
Rochelle Salt ?NaKC4H4O6 4H2O Sodium Potassium
Tantalate Tetrahydrate ? First Ferroelectric
Material Discovered ? 2 Transition Temperatures
(-18 C and 24 C) ? -18 C ? Monoclinic
Ferroelectric with point group 2 ? 24 C ? T gt
24 C Paraelectric Orthorhombic with point group
222 ? Second-Order FE-to-PE Phase Transition ? PE
Phase with Piezoelectric Properties ? Rochelle
Salt Excellent Piezoelectric Transducers Sonar,
Hydrophone, Microphone
18
Ferroelectrics with Hydrogen Bonded Radicals
Rochelle Salt
Projection of the structure on (001) plan
showing the hydrogen-bond system
19
Ferroelectrics with Hydrogen Bonded Radicals
Rochelle Salt
Temperature dependence of the dielectric constant
showing the dielectric anomalies corresponding
to two transition temperatures
20
Ferroelectrics with Hydrogen Bonded Radicals
KDP ?KH2PO4 Potassium Dihydrogen
Phosphate ? Non-Ferroelectric Phase at Room
Temperature (Tetragonal 42m) ? Non-Ferroelectric
with Piezoelectric at Room Temperature ? Curie
Temperature at 150 C ? FE Orthorhombic Phase
with point group mm2 ? First-Order FE-to-PE Phase
Transition ? KDP Good Electro-Optic and
Non-Linear Optic Properties Electro-optic
devices, High-power pulse laser Electro-optic
modulator, and Light-valve devices
21
Ferroelectrics with Hydrogen Bonded Radicals
KDP
Structural Framework of KDP (Hydrogen positions
are shown only schematically)
Ps along c-axis as a result of K and P5 ions
displacement in c-directions (Ps aligned in 180)
22
Ferroelectrics with Hydrogen Bonded Radicals
TGS ?(NH2CH2COOH)3H2SO4 Triglycine Sulfate ? FE
Phase at Room Temperature (Monoclinic point group
2) ? Curie Temperature at 49.7 C ? PE
Monoclinic Phase with point group
2/m (Paraelectric with E-induced
Piezoelectricity) ? Second-Order FE-to-PE Phase
Transition (order-disorder type) ? TGS Good
Pyroelectric Properties for Infrared
Detectors Largest response sensitivity among
known pyroelectric crystals Disadvantages include
easily depolarized (even at room temperature) (as
a result of low Tc)
23
Ferroelectrics with Hydrogen Bonded Radicals
TGS
Structure of TGS I, II, and III represent
different glycine groups Hydrogen-bonds between
Groups II and III Ordering of N in Group I
results in Ps in b-direction
24
Types of Ferroelectric Materials

• Ferroelectric Materials can be structurally
  categorized into 4 groups
• Corner Sharing Octahedra
• 1.1 Perovskite-Type Compounds
• (such as BaTiO3, PT, PZT, PMN, and PLZT)
• 1.2 Lithium Niobate and Tantalate
• (such as LiNbO3 and LiTaO3)
• 1.3 Bismuth Oxide Layer Structured Compounds
• (such as Bi4Ti3O12 and PbBi2Nb2O9)
• 1.4 Tungsten-Bronze-Type Compounds
• (such as PbNb2O6)
• Compounds Containing Hydrogen Bonded Radicals
• (such as Rochelle Salt, KDP, and TGS)
• Organic Polymers (such as PVDF and co-polymers)
• Ceramic Polymer Composites (such as PZT-PE)

Done
25
Organic Polymer Ferroelectrics
During 1940s ? Piezoelectricity in biological
materials, e.g. wood ? In the Mid
1970s ? Ferroelectricity and Pyroelectricity in
synthetic materials PVDF or PVF2 (P(VDF-TrFE), e-
irradiated P(VDF-TrFE), Polyurethane, Silicone,
and Acrylic) ? Applications utilized
Electromechanical Properties Underwater
ultrasonic transducers Electro-acoustic
transducers (microphones, earphones,
loudspeakers) Other applications button-switches c
oin-sensors
26
Organic Polymer Ferroelectrics
PVDF ? PVF2 ? (CH2-CF2)n ? Polyvinylidene
Fluoride ? P(VDF-TrFE) Co-Polymers ? TrFE ?
Tri-Fluoroethylene ? e-irradiated P(VDF-TrFE)
Co-Polymers ? Ferroelectric Materials Piezoelectri
c/Pyroelectric/Electrostrcictive
Applications Better for uses in transducers and
medical imaging applications Advantages
low-density provides little acoustical mismatch
with water and human tissues flexible and
conformable to any shape Problems large
dielectric loss at high-frequency low Tc and
degradation t low-temperature (70-100 C) low
poling efficiency in samples thicker than 1 mm
27
Organic Polymer Ferroelectrics
PVDF and P(VDF-TrFE) Co-Polymers
PVDF is a polar material by nature (due to H
and F- positions with respect to
C-atoms) Polarization can be induced by
stretching, high-temperature annealing, or
application of high electric field
28
Organic Polymer Ferroelectrics
PVDF and P(VDF-TrFE) Co-Polymers
P-E loop with different crystal forms
d31 at different poling field Ep
Polarization is induced from orienting
crystalline phase of polymer under application of
high electric field ? Piezo/Pyro Properties
depend on degree of crystallinity and FE
polarization in the crystalline phase, and also
on the poling conditions (both electric field
and temperature)
29
Organic Polymer Ferroelectrics
e-irradiated P(VDF-TrFE) Co-Polymers
Dielectric constant and loss as a function of
temperature for P(VDF-TrFE) 50/50 copolymer after
100 Mrad e-irradiation dose
P-E Loops for P(VDF-TrFE) 50/50 copolymer at room
temperature before and after e-irradiation dose
30
Organic Polymer Ferroelectrics
e-irradiated P(VDF-TrFE) Co-Polymers
Variation of remanent polarization with
temperature for P(VDF-TrFE) 50/50 copolymer
before and after e-irradiation dose
P-E Loops for P(VDF-TrFE) 50/50 copolymer at
different temperatures after 100 Mrad
e-irradiation dose
31
Organic Polymer Ferroelectrics
e-irradiated P(VDF-TrFE) Co-Polymers
Influence of irradiation on induced strain for
P(VDF-TrFE) 50/50 copolymer at room temperature
Electric field induced strain versus electric
field for P(VDF-TrFE) 50/50 copolymer at room
temperature after 100 Mrad e-irradiation dose
32
Types of Ferroelectric Materials

• Ferroelectric Materials can be structurally
  categorized into 4 groups
• Corner Sharing Octahedra
• 1.1 Perovskite-Type Compounds
• (such as BaTiO3, PT, PZT, PMN, and PLZT)
• 1.2 Lithium Niobate and Tantalate
• (such as LiNbO3 and LiTaO3)
• 1.3 Bismuth Oxide Layer Structured Compounds
• (such as Bi4Ti3O12 and PbBi2Nb2O9)
• 1.4 Tungsten-Bronze-Type Compounds
• (such as PbNb2O6)
• Compounds Containing Hydrogen Bonded Radicals
• (such as Rochelle Salt, KDP, and TGS)
• Organic Polymers (such as PVDF and co-polymers)
• Ceramic Polymer Composites (such as PZT-PE)

Done
33
Ceramic-Polymer Composites
Why composites? ? Drive for desired properties
NOT obtainable in single phase (ceramics or
polymers) ? For instance, Electromechanical
Transducers ?Requirements ? Maximum piezoelectric
sensitivity, minimum density for better
matching flexible for conformity to any curved
surface ? !! Single Phase Ceramics or Polymers DO
NOT match all these requirements !! PZT high
d33, low dh, low voltage coefficient g PVDF
highly sensitivity, low strain coefficient ? ?
Composites ? Optimize the most useful properties
of the two phases which do not ordinarily appear
together
34
Ceramic-Polymer Composites
? Made up of an active ceramic phase embedded in
a passive polymer phase ? ?Properties depend on
? Connectivity, volume percentage of ceramic
phase, and spatial distribution of the active
phase in the composite ? Connectivity (developed
by Newnham, Skinner, and Cross) ? Arrangement of
component phases within a composite ? A-B ? A
number of direction in which the active phase is
self connected B number of direction in which
the passive phase is self connected ? Diphasic
Composies 10 types 0-0, 1-0, 2-0, 3-0, 1-1,
2-1, 3-1, 2-2, 3-2, 3-3
35
Ceramic-Polymer Composites
10 Connectivity Patterns for Diphasic Composites
36
Ceramic-Polymer Composites
Connectivity of Constituent Phases in
Piezoelectric Ceramic-Polymer Composites
37
Ceramic-Polymer Composites
38
Ceramic-Polymer Composites
Volume Fraction Dependence of er, d33, g33 in 3-1
PZTPolymer Composite
39
Ceramic-Polymer Composites
Main Applications for Transducers ? ?Transducers
for Sonar ? Hydrophone an element(s) in a sonar
system used to detect ultrasound gh
hydrostatic voltage coefficient voltage induced
from applied stress dh hydrostatic charge
coefficient charge induced from applied
stress Figure of Merit (FOM) ghdh ?Medical
Transducers ? Non-ionizing, low-risk o
reproductive organs and foetus Major organs and
malfunction ? Ideal Transducer
Materials ?Requirements ? High electro-mechanical
coupling coeffcient High FOM, Low Q, Acoustic
Impedance Matching with medium ? ? Piezoelectric
Ceramic-Polymer Composites ?
40
Ceramic-Polymer Composites
Comparison of Hydrophone Figure of Merit of
Several Piezoelectric Ceramics and Transducer
Designs
41
Ceramic-Polymer Composites
Piezoelectric Composites to Use as Sensors,
Actuators, and Transducers
42
Types of Ferroelectric Materials

• Ferroelectric Materials can be structurally
  categorized into 4 groups
• Corner Sharing Octahedra
• 1.1 Perovskite-Type Compounds
• (such as BaTiO3, PT, PZT, PMN, and PLZT)
• 1.2 Lithium Niobate and Tantalate
• (such as LiNbO3 and LiTaO3)
• 1.3 Bismuth Oxide Layer Structured Compounds
• (such as Bi4Ti3O12 and PbBi2Nb2O9)
• 1.4 Tungsten-Bronze-Type Compounds
• (such as PbNb2O6)
• Compounds Containing Hydrogen Bonded Radicals
• (such as Rochelle Salt, KDP, and TGS)
• Organic Polymers (such as PVDF and co-polymers)
• Ceramic Polymer Composites (such as PZT-PE)

Done