صفحه 1:
FERROELECTRIC
CERAMICS:
properties,
processing and
applications
Ignacio Martin-Fabiani, Dai Peng, Fang Yeyu
Erica tiie. veza|
Tuesday, 17 October 2006
صفحه 2:
Introduction
= A ferroelectric ceramic mixes the
smartness of a ferroelectric material
and the tailoring possibilities of
ceramics.
= Since both kind of materials exhibit
many interesting properties, the
mixture should be good...
صفحه 3:
Ferroelectrics: ferroelectric
domains
Ferroelectric domains are generated by coupling between
dipole moments of atoms.
When subjected to electric field, the domains pointing towards
its direction start to grow over its neighbouring domains.
before poling, Pa = afterpoling, Pa 0
صفحه 4:
Ferroelectrics: hysteresis
loop
Saturation and
remanent
polarization
60
Possibility to reverse
the polarization
‘Smart material: it
keeps information
(remanent
FLOR “50
poalrization) ۰200 -200 ۰106 0 100 200 300
Electric field (kViern)
re
g
Q
2
5
a
5
ّ
0
7
صفحه 5:
Ferroelectrics: phase
transition
Ferroelectricity is a phase transition (Curie
point)
Ferroelectric phase has always lower symmetry
Example: BaTiO3 (cubic changes into tetragonal)
0
صفحه 6:
Ferroelectrics: summary
= Present spontanous polarization
= Polarization can be inversed
= Ferroelectric domains
= Hysteresis loop
= Ferroelectricity is a phase transition
= Piezoelectric and pyroelectric effect
صفحه 7:
۷
an
Ceramics is a wide
term...
= The term ceramics
covers all
inorganic non-
ل ا متللعام۳
whose formation is
due to the action of ~
heat. عم
= So you could think 5
something like
لط
صفحه 8:
...but we are dealing with
ADVANCED ceramics!
2
We can control,
modify and
optimize its
properties by
صفحه 9:
Properties of ceramics
™ Mechanical: poor toughness (under study)
= Electrical: semiconductors, superconductors,
piezoelectrics, pyroelectrics, ferroelectrics
(BaTiO,, PZT...)
= High resistance to abrasion
= Excellent hot strength
= Chemical inertness
= We can tailor properties for specific
applications
صفحه 10:
Why are ferroelectric
ceramics so important?
CERAMICS
Broad range of
chemical composition
Control of grain size,
porosity...
Possibility of varying
its shape and size.
High resistance to
abrasion
Excellent hot strength
Chemical inertness
FERROELECTRICS
High permittivities
Spontaneus
polarization
Electric conducticity
can be controlled
Piezoelectric and
pyroelectric effect
Optical anisotropy,
electrooptic an
photorefractive deffect
All this properties lead to a lot of
potential applications!
صفحه 11:
2.Processing
y of Ferroelectric
\( ceramics
Think different
صفحه 12:
1. General Procedure of
Processing
۹2
۷۵61115
۶ من
= Calcining
= Milling
= Poling
a
= Sinterin
9
™ Character
-ization *—_
™ Binder
see mOLoLr iy
صفحه 13:
1. raw
materials
Weighing the raw
materials according to
the stoichiometric
formula of the
ferroelectric ceramic
desired .
صفحه 14:
2. Mixing
Mixing the
powders either
ی 01
. routes 01 1 توا 31 ng by either ball milling or
other
ey ۳ 4 nd is more homogeneous as ۳0 ال
it is done by precipitating the precursors in the same
container.
صفحه 15:
3.Calcination
The solid phase reaction
takes place between
the constituents giving
the ferroelectric phase
during the calcination
step
صفحه 16:
+ ۰
The lumps are ground
by milling after
SUA RAE TSR 0۱۵۱۵۱۶7۱3۱۵ 2۳ ار
صفحه 17:
5. binder burnout
After shaping, the green
bodies are heated very
slowly to between 500-
600° C in order to remove
any binder present.
صفحه 18:
6.Sintering
"After the binder burnout
is over, the samples are
taken to a higher _
۱32۹0 v/a"
sintering to ta
صفحه 19:
7.Poling
= it does not show any piezoelectricity
when the ferroelectric ceramic is cooled
after sintering . Piezoelectric behavior
can be induced in a ferroelectric
ceramic by a process called "poling" .
= In this process a direct current (dc)
electric field with a strength larger than
the coercive field strength is applied to
the ferroelectric ceramic at a high
temperature, but below the Curie point.
صفحه 20:
"11
on
On the application of the
external dc field the spontaneous
polarization within each grain
gets orientated towards the
direction of the applied field.
This leads to a net polarization
in the poling direction
صفحه 21:
Two special important
methods widely uses in
the labs .
1. Metal Organic
Decomposition (MOD)
2. (2)hot-pressed solid-
state sintering method
صفحه 22:
1. MOD
"MOD: Metal Organic
Decomposition
صفحه 23:
1. spin-coat the solution on a bulk Si
wafer at 4000 rpm, 20 seconds .
2. \the film is baked on hot plate at 150 for
0 minutes to remove the solvent .
3,// then the film is given a pyrolysis heat
treatment in a furnace at 470 °Cfor 30
minutes to remove the residual organics
and promote chemical reaction
esired thickness of the film is
achieved
صفحه 24:
Tee a a LOM Ne a a سوم
سص سس
صفحه 25:
2. hot-pressed solid-
state sintering method
=SEM
micrograph of
a cross section
of PLZT
99:
ferroelectric
0 ا
صفحه 26:
hot-pressed solid-state
sintering method
= PbO, La203, ZnO, Nb205, ZrO2, and TiO2
with purity of 99.4-99.8% and micrometer
particle size were used as starting
materials. The stoichiometric mixture was
ballmilled in a plastic container with
zirconia grinding media in alcohol solution,
then dried and ground. The ground mixture
powders were pressed under 80
kg/pressure into a cylindrical bar of 60 mm
in diameter and 60 mm in height.
صفحه 27:
hot-pressed solid-state
sintering method
During a sintering process, an oxygen flow
of 3 L/min was passed through the oven.
The sintering temperature was elevated to
950 °C at a rate of 200 °C/h and kept for
1/2 h, then pressure was gradually applied
to the sample until 480 kg/ while the oven
temperature was increased to 1200 °C at
the same time.
صفحه 28:
hot-pressed solid-state
sintering method
The temperature and pressure were kept
for 6 h before the pressure was released.
Subsequently, the temperature was
continuously increased to 1250 °C in 12h
and kept for 10 h. After sintering, the oven
was cooled down to 950 °C at a rate of 140
°C/h and then cooled naturally until room
temperature. The sintered specimen was
cut and polished to obtain the required size
for different measurements.
صفحه 29:
Applications of
Ferroelectric
Ceramics ( general
overview )
صفحه 30:
background
™ Ferroelectric ceramics are used ina
very broad range of functional
ceramics and form the materials
base for the majority of electronic
applications. These electronic
applicators account for more than
60% of the total high technology
ceramics market worldwide
صفحه 31:
Capacitors
™ Basic principle
='C' is the capacitance, is the
permittivity of free space, is the
relative dielectric permittivity, 't' is
the distance between the electrodes,
‘A’ is the area of the electrodes.
صفحه 32:
(9
(MLC)
= The volumetric efficiency can be
further enhanced .
= consists of alternate layers of
dielectric and electrode material.
صفحه 33:
Ferroelectric Memories
™ FRAM (Ferroelectric Random Access Memory) is a
non-volatile memory combining both ROM and RAM
advantages in addition to non-volatility features. It has
higher speed in write mode, lower power
consumption and higher endurance
صفحه 34:
Overview of FRAM
FRAH. The Dream Memory
E
1K
Memory (bit)
صفحه 35:
Advantages over
EEPROM
= Transaction Time
- 30,000 times faster than EEROM
صفحه 36:
Energy Consumption
200 times lower power consumption
compare to EEPROM
1 FRAM Cycle is just Reading
1 EEPROM Cycle consists of erasing
صفحه 37:
Endurance
= 100,000 times higher endurance
over EEPROM and the energy
consumption is at 64Byte every
صفحه 38:
Electro-optic Applications
" Ferroelectric Thin Film
Waveguides. An optical waveguide
controls the propagation of light in a
transparent material (ferroelectric
thin film) along a certain path
= Ferroelectric Thin Film Optical
Memory Displays .
صفحه 39:
Other Ferroelectric Thin Film
Applications
= Pyroelectric Detectors :Pyroelectric
detectors are current sources with
an output proportional to the rate of
change of its temperature
صفحه 40:
Surface Acoustic Wave
Substrates
™ An elastic wave generated at the
input interdigital transducer (IDT)
travels along the surface of the
piezoelectric substrate and it is
detected by the output interdigital
transducer. These devices are
mainly used for delay lines and
filters in television and microwave
communication applications
صفحه 41:
Most Common Commercial
Ferroelectric Ceramic
صفحه 42:
Lead Zirconate Titanate (PZT)
= Chemical formula Pb Zr, Ti,, 03
= “Perovskite” ABO,
= A and B are different in size
A cation is at centre
B cation is at the corner
O atom are at centre of unit cell faces.
صفحه 43:
Lead Zirconate Titanate (PZT)
™ cenerates a voltage when some mechanical stress is
applied ... piezoelectric effect
= useful for sensor and actuator
application
™ Doping J 1
Acceptor doping intemal friction losses piezoelectric constant
1 1
Donor doping eee ae es ee
صفحه 44:
Lead Zirconate Titanate (PZT)
= Poling
High Temperature
High Voltage
* Repeat to achieve high piezoelectric
constant
صفحه 45:
PZT Thin Films
= Used in number of devices
= Thickness of 90nm
= low crystallization temperature
= good surface morphology
= high remnant polarization
صفحه 46:
Application of
۳71
Acoustic Device for
underwater Application
صفحه 47:
Acoustic Device for
underwater Application
™ Ultrasonic Sensors
= Commercial sound waves generating
devices use PZT thin films
= Bulky ferroelectric ceramic sensors
صفحه 48:
Acoustic Device for
underwater Application
" Hence
ار ۱۱۳ ۱۱:۱۱
Low fabrication cost
Film deposition techniques
[1] صم هوموبت سمط دجنع م81
[2] ومضع نمه عومتة ع
[3] دمقاندهمع0 متقوط ج10
[4] ومكع غامد دمع موقم عقمقام عه
MOCVD [5]
ECR [6]
eee ae mi
-آمة قصة
[8] هو
صفحه 49:
Fabrication
™ 0.25Um oxide layer
™ (0.3m Pt. electrode
™ PZT thin film deposition for 2 hours at 350°C
™ Annealing at 650 C for 20 minutes
™ Cooled to room temperature
صفحه 50:
Fabrication
SEM patterns of deposited PZT thin film
PZT thin film annealed at 850°C for 5 minutes
صفحه 51:
Fabrication
" Lithography used to form a window in
silicone substrate
™ Oxide layer is removed
=" 100pm diaphragm was created by
etching
™ Successive layers of Pt, PZT and Pt
deposited
" poling under an electric field of 10kV
per cm at a temperature of 130°C
صفحه 52:
Results
= Improved ferroelectric prow 3
= Improved accuracy
= Economical sensor a
= Very small and light weight
= Can be used for application
underwater
صفحه 53:
Results
22
صفحه 54:
Applications
Ultra Sonic Cleaners
SODAR
SONAR
Medical Diagnostics
Lorem ty
Gas Lighters
Micro Positioners
Retr
۷۰۹۱۱۱۱۱۵۱۵ tne acy
Sensors
Capacitors
۱۹
Ceramic resonators
Memory devices in thin film form
صفحه 55:
References of all material
and
diagrams are given in
report
صفحه 56:
Thankyou for your
kind attention !!