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Piezoelectric Materials

Lecture Outline

· Piezoelectric Phenomena

-- Piezoelectric Effect -- Modes of Vibration -- Terminology

· Materials and Processing

-- Perovskite Materials -- Ceramic Processing

· Piezoelectric Applications

-- Design Principles -- Application Examples Sensor Technology Limited

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Piezoelectric Materials

Piezoelectric Phenomena

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Piezoelectric Materials

Piezoelectric Effect

· Piezoelectric behaviour can be manifested in two distinct ways. · `direct' piezoelectric effect · `converse' piezoelectric effect

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Piezoelectric Materials

Direct Piezoelectric Effect · `Direct' piezoelectric effect occurs when a piezoelectric material becomes electrically charged when subjected to a mechanical stress. · These devices can be used to detect strain, movement, force, pressure or vibration by developing appropriate electrical responses, as in the case of force and acoustic or ultrasonic sensors.

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Piezoelectric Materials

Converse Piezoelectric Effect

· `Converse' piezoelectric effect occurs when the piezoelectric material becomes strained when placed in an electric field. · This property can be used to generate strain, movement, force, pressure or vibration through the application of suitable electric field.

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Piezoelectric Materials

Terminology

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Piezoelectric Materials

Terminology

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Piezoelectric Materials

Piezoelectric Strain Constant d

· When an electric field is applied to a piezoelectric, the material dimensions change in all three axes under stress-free conditions. The d constant also expresses the amount of charge developed relative to the stress applied along a specific axis.

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Piezoelectric Materials

Piezoelectric Strain Constant d

· The d31 constant is defined as:

d 31 = Strain Developed along 1 axis Field applied along 3 axis

Charge per electrode area = Stress applied along 1 axis

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Piezoelectric Materials

Piezoelectric Stress Constant g

· The g constant expresses the electric field developed under open circuit conditions relative to the stress applied along a specific axis. It also expresses the amount of strain induced relative to the applied electrical charge per unit area.

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Piezoelectric Materials

Piezoelectric Stress Constant g · The g31 constant is defined as:

Filed developed along 3 axis g31 = Stress applied along 1 axis Strain developed along 3 axis = Applied charge per electrode area

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Piezoelectric Materials

Hysteresis and Strain

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Piezoelectric Materials

Piezoelectric and Electrostrictive Effect

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Piezoelectric Materials

Modes of Vibration

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Piezoelectric Materials Piezoelectric Materials

Crystal, Ceramics and Polymers

Type Single Crystals Materials Quartz Lead Magnesium Niobate (PMN-PT and PZN-PT) Lead Zirconate Titanate (PZT) Lead Metaniobate (LMN) Lead Titanate (LT) Lead Magnesium Niobate (PMN) Polyvinylenedifluoride (PVDF) Ceramic-polymer Ceramic-glass

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Ceramics

Polymers Composites

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Piezoelectric Materials

Longitudinal Strain vs. Field for Various Materials

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Piezoelectric Materials

Structure of Lead Zirconate Titanate Ceramics

A2+ (Pb, Ba) B4+ (Ti, Zr) O2BM400 Type I (Pb, Sr)(Zr, Ti)O3 BM500 Type II Pb(Zr,Ti,Nb)O3 Sensor Technology Limited

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Piezoelectric Materials Piezoelectric Materials

Soft Ceramics

Type of Piezoelectric Material Soft Ceramics Normally doped with Niobium Pentoxide or Lanthanum Oxide Low Mechanical Q, High dielectric constants and high charge sensitivity. Examples of materials are: BM500 (Navy type II) BM527 (Navy type V) BM532 (Navy type VI)

Navy type ceramics refer to DOD-DTS-1376(SHIPS). Sensor Technology Limited Sensor Technology Limited

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Typical Properties Sensors, low power projectors, actuators, accelerometers.

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Hard Ceramics

Piezoelectric Materials Piezoelectric Materials

Type of Piezoelectric Material Hard Ceramics Normally doped with Nickel, Iron or Strontium. Typical characteristics are high mechanical Q, lower dielectric constant, lower loss factor, higher resistance to depoling. Examples of material are: BM400 (Navy type I) BM800 (Navy type III)

Typical Properties

High power transducers in sonar, ultrasonic cleaning, high-drive actuators, biological cell disrupters

.

Navy type ceramics refer to DOD-DTS-1376(SHIPS). Sensor Technology Limited Sensor Technology Limited

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Electrostrictive Ceramics

Type of Piezoelectric Material Electrostrictive Ceramics Normally produced from doped lead Mainly used in actuators and magnesium niobate., Available for very high power sonar projectors. about five years now, these materials have almost no hysteresis, very high dielectric constants, very high strain coefficients. Materials: BM600 (Modified Lead Magnesium Niobate)

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Piezoelectric Materials Piezoelectric Materials

Typical Properties

Piezoelectric Materials

Properties of Lead Zirconate Titanate Ceramics

Material Parameter Dielectric Constant Dissipation Factor % Voltage Constant (g31) 10-3 Vm/N Charge Constant (d31) 10-12 C/N Curie Temperature 0 C Mechanic Q Factor PZT (II) BM500 1750 2.0 -11.5 -165 360 80 PZT (VI) BM532 3250 2.0 -7.5 -250 210 70 PZT (I) BM400 1350 0.4 -10.5 -115 350 500 PZT (III) BM800 1000 0.2 -10.5 -80 325 1000

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Piezoelectric Materials

Properties of Lead Zirconate Titanate Ceramics

Application Underwater Sonar Projectors Hydrophones Depth Sounders Linear Arrays Measurement Level, Flow Flaw Detection (NDE) Accelerometers Actuators PZT (II) BM500 PZT (VI) BM532 PZT (I) BM400 r r r r r r r PZT (III) BM800 r

r r r r r r

r

r r r r

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Piezoelectric Materials

Properties of Lead Zirconate Titanate Ceramics

Application Medical Transducers Steilizers Industrial Cleaners Alarms Welders PZT (II) BM500 r PZT (VI) BM532 r PZT (I) BM400 r r r r PZT (III) BM800

r r r

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Piezoelect ric M aterials

Piezoelectric Materials

Processing of Lead Zirconate Titanate Ceramics

Weigh out raw material Ball mill Spray dry Calcine up to 1200oC Ball mill to desired particle size Spray dry Testing Sensor Technology Limited

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Powder evaluation Forming process: (dry or isostatic press etc.) Sinter firing Grinding or lapping Electroding Polarizing

Piezoelectric Materials

Polarization of Ceramics

Polarization in a single crystal of piezoelectric ceramics.

Piezoelectric ceramic before polarization

Piezoelectric ceramic after polarization

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Piezoelectric Materials

Properties of Lead Zirconate Titanate Ceramics

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Piezoelectric Materials

Standard Ceramic Configurations

Frequency discs

Thickness discs

Tubes Washers Plates and bars

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Piezoelectric Materials

Piezoelectric Tube Actuator W

A

V L = · L · d31 W

L

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Piezoelectric Materials

Electrode Configurations for Tube Actuators

Outer/Inner Electrodes Segmented 180 Deg Option 001

Outer Electrode Segmented 180 Deg Option 002

Outer/Inner Electrodes Segmented 90 Deg Option 003

Outer Electrode Segmented 90 Deg Option 004

Outer/Inner Full Face Electrodes Option 005

No Segmentation Option 005

One Horizontal Line Option 006

Horizontal/ Vertical Segments Option 007

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Piezoelectric Materials

Piezoelectric Stack Actuator

L = V · N · d 33

= V · L · d33 tE V d · A · 33 E tE s 33

A

L

F=

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Piezoelectric Materials

Actuator Displacement and Force Working Equations

Assumption: Same Electric Field in Ceramics

LS

AS

DS d 33 LS hB · · DB d31 LB LB

E FS d 33 s11 AS L B · E · · FB d 31 s33 AB hB

LB

hB

AB

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Piezoelectric Materials

Displacement and Force for Stack Actuator

For Field = 1000 V/mm Electric Field Constraints ! Coercive Field (~ 500V/mm) ! Flashover Limit in Air (~ 1000V/mm)

L 0.0006 L

would need 17mm stack for 10µm displacement.

F 30 × Area

(F in Newtons, Area in mm2 ) For 15mm OD & 5mm ID:

Note: Exceeding coercive field limit requires DC bias to avoid depoling.

F 4600 N

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Piezoelectric Materials

Bending Mode Actuator

LB DB hB

V

L2 DB = 6 · V · d 31 · B 2 hB

3 d W h FB = · V · 31 · B B E 2 s11 LB

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Piezoelectric Materials

Electrostrictive Actuator

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Di spla ce m e n t (m i cr ons).

10 8 6 4 2 0 -2 -4 -6 -20 0 -10 0 0 10 0 20 0

25 x 25 mm2

Parallel to Field

20 mm 0.5 mm

Perpendicular to Field

V o l tag e (V )

A piezoelectric actuator of the same geometry and having the same displacements at 200V would require: d33 = 1250pC/N; d31 = -460pC/N Sensor Technology Limited

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Piezoelectric Materials

Piezoelectric Composites

Piezoelectric composites consist of a ceramic material embedded in a polymer matrix with a certain connectivity known as 1-3 connectivity pattern. These elements offer several advantages over single-phase (monolithic) piezoelectric materials for such applications as hydrophones and transducers. While not a flexible element, they can be cut to very thin dimensions.

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Piezoelectric Materials

Piezoelectric Composites

Property Dielectric Constant K33T Dissipation Factor N3 Ke Q (unloaded) Ceramic Volume Frequency Sensor Technology Limited

1-3 composite BM532 525±10% 0.03 1475 ±5% 0.62 5 25-30% 150kHz 1.5MHz 3250±10% 0.03 1850±5% 0.58 70 100 150kHz 2MHz

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Piezoelectric Materials

Langevin Transducers

Langevin-type transducers feature compactness, high energy efficiency and a wide range of operating temperatures. These transducers use Lead Zirconate Titanate ceramic elements in a sandwich-type construction (two to four discs), providing a rugged unit capable of high efficiency and continuous operation at elevated temperatures. Applications: · Ultrasonic cleaning · Ultrasonic degreasers Characteristic features: · Cell disrupters · Large amplitude · Ultrasonic machining · Low heat generation · Plastics welding · Stability and durability · Underwater acoustics · High efficiency · Non-destructive evaluation · High output · Atomizers · Ultrasonic scalpel

Langevin transducers can be built from 18kHz to 70kHz for various end-user applications. A booster horn can be used to generate greater displacement from the transducer.

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Piezoelectric Materials

Piezoelectric Relations The electrical condition of an unstressed medium under the influence of an electric field is defined by two quantities - the field strength E and their dielectric displacement D. These two are related by the equation: D=E where is the permittivity of the medium.

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Piezoelectric Materials

Piezoelectric Relations The mechanical condition of the same medium at zero electric field strength can be defined by two mechanical quantities - applied stress T and strain S. S = sT where s is the compliance of the medium.

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Piezoelectric Materials

Piezoelectric Relations Piezoelectricity involves the interaction between the electrical and mechanical behaviour of the medium, and the interaction can be described by linear relationships between these two. S = sE T + dE D = dT + T E

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Piezoelectric Materials

Principles of Application 1. Energy Conversion Mechanism An externally applied electric field causes a change in the dielectric polarization in the material which in turn causes an elastic strain. The generating action takes place when an elastic strain causes a change in the polarization that induces a charge on the electrodes.

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Piezoelectric Materials

Principles of Application 2. Transducer Operating Environment The acoustic properties of the medium (air, water or ice) are very important in the design of transducers. Transducers must also withstand the severe effects of sea water, biological activity, hydrostatic pressure, and extreme temperature conditions.

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Piezoelectric Materials

Principles of Application 3. Conversion Criteria

The following are the general performance criteria for the transducers. · Linearity. The output of the transducer is a linear function of the input. · Reversibility. The transducer must convert energy in either direction. · Passivity. All the output energy from the transducer is obtained from the input energy - electrical or acoustical.

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Piezoelectric Materials

Applications

Mechanical to Electrical Conversion

!

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Phonograph cartridges Microphones Vibration sensors Accelerometers Photoflash actuators Gas igniters Fuses

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Piezoelectric Materials

Applications - Piezoelectric Igniters

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Piezoelectric Materials

Applications - Piezoelectric Igniters

NTK Ceramics, Japan, 1986.

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Piezoelectric Materials

Hydrophones

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Piezoelectric Materials

Applications - Diver Communication Systems

Ocean technology Systems, 1990

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Piezoelectric Materials

Applications - Marine Mammal Listening Systems

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Piezoelectric Materials

Applications - Consumer Products

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Piezoelectric Materials

Applications

Electrical to Mechanical Conversion

!

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Valves Micropumps Earphones and speakers Ultrasonic cleaners Emulsifiers Sonic transducers

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Piezoelectric Materials

Applications - Piezoelectric Audiotone Transducers

Figure A. Layered structure with ceramic bonded to metal diaphragm. Radial mode of vibration produces a bending effect. Figure B. Alternating voltage produces convex and concave distortions in the diaphragm. Displacement of the diaphragm is in the order of microns. Sensor Technology Limited

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Piezoelectric Materials

Applications - Liquid Atomization Devices

1

2

3

1. Vibration; 2. Cavitation; 3. Misting 4. Ultrasonic Humidifier.

4

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Piezoelectric Materials

Applications - Liquid Atomization Devices

Liquid Atomizing Nozzle from Sono-Tek Corporation. Fine liquid sprays are used in material processing industry such as the manufacture of solar cells to provide thin uniform coatings.

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Piezoelectric Materials

Applications - Liquid Atomization Devices

Data from Sono-Tek

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Piezoelectric Materials

Applications - Liquid Atomization Devices

Misting (at increased power levels)

Cavitation (at lower power levels)

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Piezoelectric Materials

Applications - Depth Sounders

NTK Technical Ceramics, 1986.

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Piezoelectric Materials

Applications - Sonar Applications

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Piezoelectric Materials

Applications - Low Frequency Sonar

Sonar Dome

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Piezoelectric Materials

Applications - Low Frequency Sonar Detail of the Sonar Transducer and the components of the system.

Raytheon, 1984.

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Piezoelectric Materials

Applications - Ultrasonic Motor

Shinsei, 1996

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Piezoelectric Materials

Applications

ElectricalMechanicalElectrical Conversion

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!

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Surface acoustic wave devices Delay lines Filters Oscillators Transformers

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Piezoelectric Materials

Applications - Flash Blindness Goggles

Aura

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Piezoelectric Materials Piezoelectric Materials

Transducer Depth Matching SX100 Compensator Network Shield Power Amplifier Signal Processor Power Lithium Distribution Battery Board Pack

Anodized Aluminum Housing

Underwater Communications

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Piezoelectric Materials Piezoelectric Materials

Battery

Cable & Reel

Control Box Transducer

Communication with Marine Mammals

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Piezoelectric Materials Piezoelectric Materials

Transmitter

Receiver/Monitor

Marine Mammal Communications

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Piezoelectric Materials

Conclusions

NTK Technical Ceramics, 1986.

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Piezoelectric Materials

Conclusions

· Reviewed Piezoelectric Phenomena

-- Piezoelectric Effect, Modes of Vibration, Terminology

· Materials and Processing · Piezoelectric Applications

-- Application examples using mechanical to electrical conversion, electrical to mechanical conversion, and electrical-mechanical-electrical conversion have been discussed.

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