Some Applications of Ferroelectric Ceramics1. Capacitors2. Ferroelectric Thin Films

2.1 Ferroelectric Memories2.2 Electro-Optic Applications

2.2.1 Thin Film Waveguides2.2.2 Thin Film Optical Memories and Displays2.2.3 Thin Film Capacitors2.2.4 Pyroelectric Detectors2.2.5 Surface Acoustic Wave Substrates

Some Applications of Piezoelectric Ceramics1. Medical Ultrasound Applications2. Gas Ignitors3. Displacement Transducers4. Accelerometers5. Piezoelectric Transformers6. Impact Printer Head7. Precision X-Y Stage

CapacitorsA parallel plate capacitor made of a dielectric material sandwiched

between two electrodes

C = orA/d

C is the capacitance , r the relative dielectric permittivityA 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 r small disk capacitor (> 50 % of the ceramic capacitor market)

The Volume Efficiency greatly enhanced by

Multilayer Ceramic Capacitors (MLC)Tape Casting Technique

Ferroelectric Thin FilmApplications for electronic and electro-optic devices

Materials of InterestBT, PT, PZT, PMN Perovskite

Bi4Ti3012, (Pb, Ba)Nb2O6

Applications

Electronicnon-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 MemoriesDynamic Random Access Memories (DRAMs)

Static Random Access Memories (SRAMs)

Disadvantages : Volatile (lost of information when out of power)

Solutions are with Non-Volatile MemoriesComplementary Metal Oxide Semiconductor (CMOS) (with back-up battery)

Electrically Erasable Read Only Memories (EEPROMs)

Disadvantages : Very Expensive

Possible Solution with Non-Volatile Ferroelectric MemoriesFerroelectric Random Access Memories (FRAMs)High Speed (30 ns cycle time for read/erase/rewrite)

High Density (4 m2 cell size)

Ferroelectric Thin Film MemoriesFerroelectric Random Access Memories (FRAMs)

Storing data using the reversible polarization mechanism of ferroelectrics“Polarization Switching”

Non-Volatile Memories

Hysteresis Properties : Remnant Polarization after Field Removed

Thin Film Fabrications with PVD, CVD, LPE, EGM, MBE, Laser, or Sol-Gel

Several Critical Processing ParametersEc, 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-OpticsFerroelectric Thin Film for Optical Memories and Displays

Replacing PLZT bulk ceramics

Advantages of thin films

Simplification of the display devicesLower operating voltage

Require large electro-optic coefficients

Strong photosensitivities for the film PZT and PLZT

Ferroelectric Thin Film for Electronics

Thin Film Capacitors

Large volume efficiency

BT and PMN are mostly choice of materials

Ferroelectric Thin Film for Pyroelectric Detectors

Heat sensing applications

Advantages of thin filmsLow cost fabrication, as compared with

single crystalsConvenient geometry for device design

Materials of InterestTGS, LiTaO3, (Sr, Ba)Nb2O6, PT, La-

PT, and PZT

Thin Film for Surface Acoustic Wave (SAW)

Substrates

Interdigital electrodes as SAW detector functionality

LiNbO3, LiTaO3, PZT

Delay lines and filter

applications in television and microwave communication

Ferroelectric Thin Film for Electronics

Piezoelectric Ceramic ApplicationsMedical Ultrasound Applications

Piezoelectric ceramics : Active and Passive Transducers

Passive : Sound receiver

Active : Sound transmitter

Pulse Echo Mode : Both active and passive functionssound waves penetrate the medium with faint echo

Ultrasound imaging is done without the cutting/surgeryResolution better than X-rays (which can done in bones)

Lower power levels

Pulse Echo method employed

Frequency span between 1.5-30 MHz

Piezoelectric Ceramic ApplicationsApplications in large frequency span

Operating Frequency depends on samples and organs to be diagnosed

2-5 MHz: Abdominal, Obstetrical, Cardiological applications5-7.5 MHz : Pediatric and peripheral vascular applications

10-30 MHz : Intravascular, intracardiac, eye-imaging applications

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)

Impedance Z issueMatching layer at the interface

Soft PZT ceramics are widely used for medical imaging

Piezoelectric Ceramic ApplicationsGas Ignitors

Voltage generator consists of two oppositely pole ceramic cylinders and

attached end to end to double the charge available for the spark

Two Stages Process for Spark Generation

1. Force F on ceramic causes change of dL (under open circuit)

2. Discharge through gap causes closed circuit

Piezoelectric Ceramic ApplicationsDisplacement Transducers

Bimorph Configuration

Two long poled piezoelectric ceramic specimens bond together

1. Force F on the cantilever beam results in induced electric field

Piezoelectric Ceramic ApplicationsDisplacement Transducers

Bimorph Configuration

Two long poled piezoelectric ceramic specimens bond together

2. Electric Field E on the cantilever beam results in induced bending

Piezoelectric Ceramic ApplicationsAccelerometers

Device that gives an electrical output proportional to acceleration

Shear mode utilized

Poled along axis, but another new electrodes in inner and outer parts of the tube

Piezoelectric Ceramic ApplicationsPiezoelectric Transformer

Low-to-High Voltage Transformer with piezoeletric plates

Electrode configurations vary, samples are poled separately in different direction

A length mode is excited in the large area by AC field

Piezoelectric Ceramic ApplicationsImpact Printer Head

Dot-matrix printer driven by piezoelectric ceramic actuators

Precision XY stage

Piezoelectric Actuators

Piezoelectric Ceramic ApplicationsOther Examples of Applications of Piezoelectric Ceramics

ActuatorsPrecision motion control, autofocusing cameras ink-jet printer, positioning

VCR head, micromachining metals, valves

Ultrasonic MotorsCompact and high efficiency motors

Delay Lines and Wave FiltersDelay Line : in TV and other household appliances

Wave Filters : resonant behavior of piezoelectric ceramics/quartz

Sonic Energy GenerationHigh-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)