2B1750 06 Ferroelectric Ceramics

8/8/2019 2B1750 06 Ferroelectric Ceramics

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FERROELECTRICFERROELECTRICCERAMICS:CERAMICS:

properties, processingproperties, processingand applicationsand applications

Ignacio MartinIgnacio Martin--Fabiani, Dai Peng, Fang Yeyu and Sohaib AfzalFabiani, Dai Peng, Fang Yeyu and Sohaib Afzal

Tuesday, 17 October 2006Tuesday, 17 October 2006


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Ferroelectrics: ferroelectric domainsFerroelectrics: ferroelectric domains

Ferroelectric domains are generated by coupling between dipoleFerroelectric domains are generated by coupling between dipolemoments of atoms.moments of atoms.

When subjected to electric field, the domains pointing towards itsWhen subjected to electric field, the domains pointing towards itsdirection start to grow over its neighbouring domains.direction start to grow over its neighbouring domains.


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Ferroelectrics: hysteresis loopFerroelectrics: hysteresis loop

Saturation and remanentSaturation and remanentpolarizationpolarization

Coercive fieldCoercive field

Possibility to reverse thePossibility to reverse thepolarizationpolarization

Smart material: it keepsSmart material: it keeps

information (remanentinformation (remanentpoalrization)poalrization)


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Ferroelectrics: summaryFerroelectrics: summary

Present spontanous polarizationPresent spontanous polarization

Polarization can be inversedPolarization can be inversed

Ferroelectric domainsFerroelectric domains Hysteresis loopHysteresis loop

Ferroelectricity is a phase transitionFerroelectricity is a phase transition

Piezoelectric and pyroelectric effectPiezoelectric and pyroelectric effect


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Ceramics is a wide termCeramics is a wide term

The term ceramicsThe term ceramicscovers all inorganic noncovers all inorganic non--metallic materials whosemetallic materials whose

formation is due to theformation is due to theaction of heat.action of heat.

So you could thinkSo you could thinksomething like thissomething like this


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but we are dealing withbut we are dealing with

ADVANCED ceramics!ADVANCED ceramics!

We can control, modifyWe can control, modify

and optimize itsand optimize its

properties by tailoringproperties by tailoring

the material!the material!


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Properties of ceramicsProperties of ceramics

Mechanical: poor toughness (under study)Mechanical: poor toughness (under study)

Electrical: semiconductors, superconductors,Electrical: semiconductors, superconductors,

piezoelectrics, pyroelectrics, ferroelectricspiezoelectrics, pyroelectrics, ferroelectrics(BaTiO(BaTiO33, PZT), PZT)

High resistance to abrasionHigh resistance to abrasion

Excellent hot strengthExcellent hot strength Chemical inertnessChemical inertness

We can tailor properties for specific applicationsWe can tailor properties for specific applications


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Why are ferroelectric ceramics soWhy are ferroelectric ceramics so

important?important?FERROELECTRICSFERROELECTRICS

High permittivitiesHigh permittivities

Spontaneus polarizationSpontaneus polarization

Electric conducticity can beElectric conducticity can becontrolledcontrolled

Piezoelectric and pyroelectricPiezoelectric and pyroelectriceffecteffect

Optical anisotropy,Optical anisotropy,electrooptic anelectrooptic an

photorefractive deffectphotorefractive deffect

CERAMICSCERAMICS

Broad range of chemicalBroad range of chemicalcompositioncomposition

Control of grain size,Control of grain size,porosityporosity

Possibility of varying itsPossibility of varying itsshape and size.shape and size.

High resistance to abrasionHigh resistance to abrasion Excellent hot strengthExcellent hot strength

Chemical inertnessChemical inertness

All this properties lead to a lot of potential

applications!


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2.Processing2.Processing

ofFerroelectricofFerroelectricceramicsceramics


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1. General Procedure of Processing1. General Procedure of Processing

RawRaw

MaterialsMaterials MixingMixing

SinteringSintering

CalciningCalcining

MillingMilling CharacterCharacter

--izationization PolingPoling

BinderBinder

BurnoutBurnout


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1. raw materials1. raw materials

Weighing the raw materialsWeighing the raw materialsaccording to the stoichiometricaccording to the stoichiometric

formula of the ferroelectricformula of the ferroelectricceramic desiredceramic desired ..


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2. Mixing2. Mixing

Mixing the powdersMixing the powders

either mechanically oreither mechanically orchemicallychemically

Mechanical mixing is usually done by either ball milling orMechanical mixing is usually done by either ball milling orattrition milling for a short time.attrition milling for a short time.

Chemical mixing on the other hand is more homogeneous asChemical mixing on the other hand is more homogeneous as

it is done by precipitating the precursors in the same container.it is done by precipitating the precursors in the same container.


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3.Calcination3.Calcination

The solid phase reaction takesThe solid phase reaction takes

place between the constituentsplace between the constituentsgiving the ferroelectric phasegiving the ferroelectric phaseduring the calcination stepduring the calcination step


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4. Milling4. Milling

The lumps are ground byThe lumps are ground by

milling after calcining.milling after calcining.


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5. binder burnout5. binder burnout

After shaping, the green bodies areAfter shaping, the green bodies are

heated very slowly to betweenheated very slowly to between

500500--600600 C in order to removeC in order to remove

any binder present.any binder present.


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6.Sintering6.Sintering

After the binder burnout is over,After the binder burnout is over,

the samples are taken to athe samples are taken to ahigher temperature for sinteringhigher temperature for sinteringto take place.to take place.


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7.Poling7.Poling it does not show any piezoelectricity when theit does not show any piezoelectricity when the

ferroelectric ceramic is cooled after sintering .ferroelectric ceramic is cooled after sintering .Piezoelectric behavior can be induced in aPiezoelectric behavior can be induced in a

ferroelectric ceramic by a process calledferroelectric ceramic by a process called"poling" ."poling" .

In this process a direct current (dc) electric fieldIn this process a direct current (dc) electric field

with a strength larger than the coercive fieldwith a strength larger than the coercive fieldstrength is applied to the ferroelectric ceramic atstrength is applied to the ferroelectric ceramic ata high temperature, but below the Curie point.a high temperature, but below the Curie point.


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8.Characterization8.Characterization

On the application of the external dcOn the application of the external dcfield the spontaneous polarizationfield the spontaneous polarization

within each grain gets orientatedwithin each grain gets orientatedtowards the direction of the appliedtowards the direction of the appliedfield. This leads to a net polarization infield. This leads to a net polarization in

the poling directionthe poling direction


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Two special important methodsTwo special important methods

widely uses in the labswidely uses in the labs ..

1.1. Metal Organic DecompositionMetal Organic Decomposition

(MOD)(MOD)2.2. (2)hot(2)hot--pressed solidpressed solid--statestate

sintering methodsintering method


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1. MOD1. MOD

MOD:MOD: Metal OrganicMetal OrganicDecompositionDecomposition


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DesiredDesired thickness of the film is achievedthickness of the film is achieved

1.1. spinspin--coat the solution on a bulk Si wafer atcoat the solution on a bulk Si wafer at

4000 rpm, 20 seconds .4000 rpm, 20 seconds .2.2. the film is baked on hot plate at 150 for 10the film is baked on hot plate at 150 for 10

minutes to remove the solvent .minutes to remove the solvent .3.3. then the film is given a pyrolysis heatthen the film is given a pyrolysis heat

treatment in a furnace at 470treatment in a furnace at 470for 30for 30minutes to remove the residual organicsminutes to remove the residual organicsand promote chemical reactionand promote chemical reaction


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Ferroelectric BST-thick film ceramic on an

alumina substrate


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2. hot2. hot--pressed solidpressed solid--statestate

sintering methodsintering method

SEM micrographSEM micrograph

of a cross sectionof a cross sectionof PLZTof PLZT

transparenttransparent

ferroelectricferroelectricceramics.ceramics.


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hothot--pressed solidpressed solid--state sintering methodstate sintering method

PbO, La2O3, ZnO, Nb2O5, ZrO2, and TiO2 withPbO, La2O3, ZnO, Nb2O5, ZrO2, and TiO2 withpurity of 99.4purity of 99.499.8% and micrometer particle size were99.8% and micrometer particle size wereused as starting materials. The stoichiometric mixtureused as starting materials. The stoichiometric mixture

was ballmilled in a plastic container with zirconiawas ballmilled in a plastic container with zirconiagrinding media in alcohol solution, then dried andgrinding media in alcohol solution, then dried andground. The ground mixture powders were pressedground. The ground mixture powders were pressedunder 80 kg/pressure into a cylindrical bar of 60 mm inunder 80 kg/pressure into a cylindrical bar of 60 mm in

diameter and 60 mm in height.diameter and 60 mm in height.


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During a sintering process, an oxygen flow of 3 L/minDuring a sintering process, an oxygen flow of 3 L/min

was passed through the oven. The sinteringwas passed through the oven. The sintering

temperature was elevated to 950temperature was elevated to 950C at a rate of200C at a rate of200

C/h and kept for 12 h, then pressure was graduallyC/h and kept for 12 h, then pressure was graduallyapplied to the sample until 480 kg/ while the ovenapplied to the sample until 480 kg/ while the oven

temperature was increased to 1200temperature was increased to 1200C at the sameC at the same

timetime..


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The temperature and pressure were kept for 6 h beforeThe temperature and pressure were kept for 6 h beforethe pressure was released. Subsequently, thethe pressure was released. Subsequently, the

temperature was continuously increased to 1250temperature was continuously increased to 1250C inC in

12 h and kept for 10 h. After sintering, the oven was12 h and kept for 10 h. After sintering, the oven wascooled down to 950cooled down to 950C at a rate of140C at a rate of140C/h andC/h andthen cooled naturally until room temperature. Thethen cooled naturally until room temperature. Thesintered specimen was cut and polished to obtain thesintered specimen was cut and polished to obtain the

required size for different measurements.required size for different measurements.


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Applications ofApplications ofFerroelectric CeramicsFerroelectric Ceramics

(( general overviewgeneral overview))


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backgroundbackground

Ferroelectric ceramics are used in a very broadFerroelectric ceramics are used in a very broad

range of functional ceramicrange of functional ceramicssand form theand form thematerials base for the majority of electronicmaterials base for the majority of electronic

applications. These electronic applicatorsapplications. These electronic applicatorsaccount for more than 60% of the total highaccount for more than 60% of the total high

technology ceramics market worldwidetechnology ceramics market worldwide


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CapacitorsCapacitors

Basic principleBasic principle

'C' is the capacitance, is the permittivity of free'C' is the capacitance, is the permittivity of freespace, is the relative dielectric permittivity, 't' isspace, is the relative dielectric permittivity, 't' is

the distance between the electrodes, 'A' is thethe distance between the electrodes, 'A' is thearea of the electrodes.area of the electrodes.

0( )rAC

t

I I

!

0I

rI


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multilayer ceramic (MLC)multilayer ceramic (MLC)

The volumetric efficiency can be furtherThe volumetric efficiency can be further

enhanced .enhanced .

consists of alternate layers of dielectric andconsists of alternate layers of dielectric andelectrode material.electrode material.

0( )rn A

C t

I I

!


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Ferroelectric MemoriesFerroelectric Memories

FRAM (Ferroelectric Random Access Memory)FRAM (Ferroelectric Random Access Memory)

is a nonis a non--volatile memory combining both ROMvolatile memory combining both ROMand RAM advantages in addition to nonand RAM advantages in addition to non--

volatility features. It has higher speed in writevolatility features. It has higher speed in writemode, lower power consumption and highermode, lower power consumption and higher

enduranceendurance


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Overview of FRAMOverview of FRAM


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Advantages over EEPROMAdvantages over EEPROM

Transaction TimeTransaction Time

-- 30,000 times faster than EEROM30,000 times faster than EEROM


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Energy ConsumptionEnergy Consumption

200 times lower power consumption compare to200 times lower power consumption compare toEEPROMEEPROM

1FRAM Cycle is just Reading1FRAM Cycle is just Reading

1 EEPROM Cycle consists of erasing , writing and1 EEPROM Cycle consists of erasing , writing andreadingreading


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EnduranceEndurance

100,000 times higher endurance over EEPROM100,000 times higher endurance over EEPROM

and the energy consumption is at 64Byte everyand the energy consumption is at 64Byte everywrite cyclewrite cycle


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ElectroElectro--optic Applicationsoptic Applications

FerroelectricThinFilmWaveguides. AnopticalFerroelectricThinFilmWaveguides. Anoptical

waveguidecontrolsthepropagationoflightinawaveguidecontrolsthepropagationoflightina

transparentmaterial(ferroelectricthinfilm) alongatransparentmaterial(ferroelectricthinfilm) alonga

certainpathcertainpath

FerroelectricThinFilmOpticalMemoryDisplaysFerroelectricThinFilmOpticalMemoryDisplays..


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Other Ferroelectric Thin FilmOther Ferroelectric Thin FilmApplicationsApplications

PyroelectricDetectorsPyroelectricDetectors:Pyroelectric detectors are:Pyroelectric detectors are

current sources with an output proportional tocurrent sources with an output proportional tothe rate of change of its temperaturethe rate of change of its temperature


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SurfaceAcousticWaveSubstratesSurfaceAcousticWaveSubstrates

An elastic wave generated at the inputAn elastic wave generated at the input

interdigital transducer (IDT) travels along theinterdigital transducer (IDT) travels along thesurface of the piezoelectric substrate and it issurface of the piezoelectric substrate and it is

detected by the output interdigital transducer.detected by the output interdigital transducer.These devices are mainly used for delay lines andThese devices are mainly used for delay lines and

filters in television and microwavefilters in television and microwave

communication applicationscommunication applications


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Most Common CommercialMost Common CommercialFerroelectric CeramicFerroelectric Ceramic


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Lead Zirconate Titanate (PZT)Lead Zirconate Titanate (PZT)

Chemical formulaChemical formula Pb ZrPb ZrxxTiTi11--xx OO33 PerovskitePerovskite ABOABO33

A and B are different in sizeA and B are different in sizeA cation is at centreA cation is at centre

B cation is at the cornerB cation is at the corner

O atom areO atom are at centre of unit cell faces.at centre of unit cell faces.


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generates a voltage when some mechanical stressgenerates a voltage when some mechanical stress

is appliedis applied piezoelectric effectpiezoelectric effect

useful for sensor and actuator applicationuseful for sensor and actuator application DopingDoping

Acceptor dopingAcceptor doping internal friction losses piezoelectric constantinternal friction losses piezoelectric constant

Donor dopingDonor doping internal friction losses piezoelectric constantinternal friction losses piezoelectric constant


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PolingPoling

High TemperatureHigh Temperature

High VoltageHigh Voltage Repeat to achieve highRepeat to achieve high piezoelectric constanpiezoelectric constantt


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PZT Thin FilmsPZT Thin Films

Used in number of devicesUsed in number of devices

Thickness of 90nmThickness of 90nm

low crystallization temperaturelow crystallization temperature good surface morphologygood surface morphology

high remnant polarizationhigh remnant polarization


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Application of PZTApplication of PZT

Acoustic Device for underwaterAcoustic Device for underwater

ApplicationApplication

A i D i f dA i D i f d


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Acoustic Device for underwaterAcoustic Device for underwaterApplicationApplication

Ultrasonic SensorsUltrasonic Sensors

Commercial sound waves generating devices useCommercial sound waves generating devices use

PZT thin filmsPZT thin films Bulky ferroelectric ceramic sensorsBulky ferroelectric ceramic sensors


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Acoustic Device for underwaterAcoustic Device for underwaterApplicationApplication

HenceHence

Thin films are usedThin films are used

Low fabrication costLow fabrication cost

Film deposition techniquesFilm deposition techniquesElectron beam evaporation [1]Electron beam evaporation [1]

Rf diode sputtering [2]Rf diode sputtering [2]

Ion beam deposition [3]Ion beam deposition [3]

RF planar magnetron sputtering [4]RF planar magnetron sputtering [4]

MOCVD [5]MOCVD [5]

ECR [6]ECR [6]

laser ablation [7]laser ablation [7]

and soland sol--gelgel[8][8]


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FabricationFabrication

0.250.25 m oxide layerm oxide layer

0.30.3 m Pt. electrodem Pt. electrode

PZT thin film deposition for 2 hours at 350CPZT thin film deposition for 2 hours at 350CAnnealing at 650C for 20 minutesAnnealing at 650C for 20 minutes

Cooled to room temperatureCooled to room temperature


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SEM patterns of deposited PZT thin filmSEM patterns of deposited PZT thin film

PZT thin film annealed at 850C for 5 minutesPZT thin film annealed at 850C for 5 minutes


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Lithography used to form a window in siliconeLithography used to form a window in silicone

substratesubstrate

Oxide layer is removedOxide layer is removed 100 m diaphragm was created by etching100 m diaphragm was created by etching

Successive layers of Pt, PZT and Pt depositedSuccessive layers of Pt, PZT and Pt deposited

poling under an electric field of 10kV per cm atpoling under an electric field of 10kV per cm ata temperature of130Ca temperature of130C


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ResultsResults

Improved ferroelectric propertyImproved ferroelectric property

Improved accuracyImproved accuracy

Economical sensorEconomical sensorVery small and light weightVery small and light weight

Can be used for application underwaterCan be used for application underwater


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ResultsResults

SenstivitySenstivity


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ApplicationsApplications

Ultra Sonic CleanersUltra Sonic Cleaners SODARSODAR

SONARSONAR Medical DiagnosticsMedical Diagnostics

Printer HeadsPrinter Heads

Gas LightersGas Lighters Micro PositionersMicro Positioners ActuatorsActuators

AnnunciatorsAnnunciators SensorsSensors

CapacitorsCapacitors F

RAMF

RAM

Ceramic resonatorsCeramic resonators Memory devices in thin film formMemory devices in thin film form


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References of all material andReferences of all material anddiagrams are given in reportdiagrams are given in report


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Thankyou for your kindThankyou for your kind

attention !!attention !!

2B1750 06 Ferroelectric Ceramics

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