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Some Applications of Ferroelectric Ceramics
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2.
Capacitors
Ferroelectric Thin Films
2.1 Ferroelectric Memories
2.2 Electro-Optic Applications
2.2.1 Thin Film Waveguides
2.2.2 Thin Film Optical Memories and Displays
2.2.3 Thin Film Capacitors
2.2.4 Pyroelectric Detectors
2.2.5 Surface Acoustic Wave Substrates
Some Applications of Piezoelectric Ceramics
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Medical Ultrasound Applications
Gas Ignitors
Displacement Transducers
Accelerometers
Piezoelectric Transformers
Impact Printer Head
Precision X-Y Stage
Capacitors
A parallel plate capacitor made of a dielectric material sandwiched
between two electrodes
C = eoerA/d
C is the capacitance , er the relative dielectric permittivity
A the area of the electrode, d the thickness of the dielectric
High volume efficiency arises from large relative dielectric
permittivity, large area, and small thickness
BaTiO3 very high er  small disk capacitor
(> 50 % of the ceramic capacitor market)
The Volume Efficiency greatly enhanced by
Multilayer Ceramic Capacitors (MLC)
Tape Casting Technique
Ferroelectric Thin Film
Applications for electronic and electro-optic devices
Materials of Interest
BT, PT, PZT, PMN Perovskite
Bi4Ti3012, (Pb, Ba)Nb2O6
Applications
Electronic
non-volatile memories, thin-film capacitors, pyroelectric
sensors, surface acoustic wave (SAW) substrates
Electro-optic
optical waveguide and optical memories and displays
Ferroelectric Thin Film Memories
Current Dominating Market is based on Semiconductor Memories
Dynamic Random Access Memories (DRAMs)
Static Random Access Memories (SRAMs)
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Disadvantages : Volatile (lost of information when out of power)
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Solutions are with Non-Volatile Memories
Complementary Metal Oxide Semiconductor (CMOS) (with back-up battery)
Electrically Erasable Read Only Memories (EEPROMs)
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Disadvantages : Very Expensive
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Possible Solution with Non-Volatile Ferroelectric Memories
Ferroelectric Random Access Memories (FRAMs)
High Speed (30 ns cycle time for read/erase/rewrite)
High Density (4 mm2 cell size)
Ferroelectric Thin Film Memories
Ferroelectric Random Access Memories (FRAMs)
Storing data using the reversible polarization mechanism of ferroelectrics
“Polarization Switching”
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Non-Volatile Memories
Hysteresis Properties : Remnant Polarization after Field Removed
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Thin Film Fabrications with PVD, CVD, LPE, EGM, MBE, Laser, or Sol-Gel
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Several Critical Processing Parameters
Ec, Pr, Hysteresis Characteristics
Small Film Thickness is better to minimize switching field
(200-300 nm thick films require ~ 5 V potential for switching)
Interface with substrate to minimize non-ferroelectric phases
Inert electrode with PZT film at high temperature
Minimize “fatigue” problem from which FRAMs lose memory with time
(Fatigue resistance of 1012 cycles is required)
Extensive On-Going Research
Ferroelectric Thin Film for Electro-Optics
Ferroelectric Thin Film for Optical Memories and Displays
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Replacing PLZT bulk ceramics
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Advantages of thin films
Simplification of the display devices
Lower operating voltage
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Require large electro-optic coefficients
Strong photosensitivities for the film PZT and PLZT
Ferroelectric Thin Film for Electronics
Thin Film Capacitors
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Large volume efficiency
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BT and PMN are mostly choice of materials
Ferroelectric Thin Film for Electronics
Ferroelectric Thin Film for
Pyroelectric Detectors
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Heat sensing applications
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Advantages of thin films
Low cost fabrication, as compared with
single crystals
Convenient geometry for device design
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Materials of Interest
TGS, LiTaO3, (Sr, Ba)Nb2O6, PT, LaPT, and PZT
Thin Film for Surface
Acoustic Wave (SAW)
Substrates
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Interdigital electrodes as SAW
detector functionality
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LiNbO3, LiTaO3, PZT
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Delay lines and filter
applications in television and
microwave communication
Piezoelectric Ceramic Applications
Medical Ultrasound Applications
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Piezoelectric ceramics : Active and Passive Transducers
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Passive : Sound receiver
Active : Sound transmitter
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Pulse Echo Mode : Both active and passive functions
sound waves penetrate the medium with faint echo
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Ultrasound imaging is done without the cutting/surgery
Resolution better than X-rays (which can done in bones)
Lower power levels
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Pulse Echo method employed
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Frequency span between 1.5-30 MHz
Piezoelectric Ceramic Applications
Applications in large frequency span
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Operating Frequency depends on samples and organs to be diagnosed
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2-5 MHz: Abdominal, Obstetrical, Cardiological applications
5-7.5 MHz : Pediatric and peripheral vascular applications
10-30 MHz : Intravascular, intracardiac, eye-imaging applications
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Resolution at a certain frequency is calculated from c = 
Human body, c ~ 1500 m/s  Resolution varies 1-50 mm
( when frequency ~ 1.5-30 MHz)
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Impedance Z issue
Matching layer at the interface
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Soft PZT ceramics are widely used for medical imaging
Piezoelectric Ceramic Applications
Gas Ignitors
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Voltage generator consists of two oppositely pole ceramic cylinders and attached
end to end to double the charge available for the spark
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Two Stages Process for Spark Generation
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1. Force F on ceramic causes change of dL (under open circuit)
2. Discharge through gap causes closed circuit
Piezoelectric Ceramic Applications
Displacement Transducers
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Bimorph Configuration
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Two long poled piezoelectric ceramic specimens bond together
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1. Force F on the cantilever beam results in induced electric field
Piezoelectric Ceramic Applications
Displacement Transducers
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Bimorph Configuration
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Two long poled piezoelectric ceramic specimens bond together
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2. Electric Field E on the cantilever beam results in induced bending
Piezoelectric Ceramic Applications
Accelerometers
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Device that gives an electrical output proportional to acceleration
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Shear mode utilized
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Poled along axis, but another new electrodes in inner and outer parts of the tube
Piezoelectric Ceramic Applications
Piezoelectric Transformer
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Low-to-High Voltage Transformer with piezoeletric plates
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Electrode configurations vary, samples are poled separately in different direction
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A length mode is excited in the large area by AC field
Piezoelectric Ceramic Applications
Impact Printer Head
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Dot-matrix printer driven by piezoelectric ceramic actuators
Precision XY stage
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Piezoelectric Actuators
Piezoelectric Ceramic Applications
Other Examples of Applications of Piezoelectric Ceramics
Actuators
Precision motion control, autofocusing cameras ink-jet printer, positioning
VCR head, micromachining metals, valves
Ultrasonic Motors
Compact and high efficiency motors
Delay Lines and Wave Filters
Delay Line : in TV and other household appliances
Wave Filters : resonant behavior of piezoelectric ceramics/quartz
Sonic Energy Generation
High-Fi Tweeter made from circular bimorph
Others: Generators ( solid-state batteries), Sonic and Ultrasonic
Transducers (buzzers, microphones, speakers, echo-sounders,
atomizers, welding equipment, cleaning process), Sensors
(pressure sensors, knock sensors)