piezo ceramic actuators & custom subassemblies

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Piezo Ceramic Actuators

& Custom Subassemblies

1484_PI_Ceramic_Katalog.qxd 12.01.2004 13:50 Uhr Seite 1

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PI Ceramic piezoelectric actua-tors offer today’s motion engi-neer and scientist a practicalway to achieve extremely highpositioning accuracy, shortestpossible response times, bestdynamic operation and largestforces in a wide variety ofapplications. Presently piezo-electric actuator based motionsystems increasingly replaceclassical motion technolo-gies—improving products interms of miniaturization, preci-sion and throughput. In addi-tion, the unique features ofpiezoelectric actuators will trig-ger the development of motionequipment that could not evenexist without this technology.

PI Ceramic, a member of thePI Group, offers the largestselection worldwide of re-search- and industrial-reliabilitypiezoelectric actuators. In addi-tion to the standard piezoelec-tric products presented in thisshort catalog, we focus on cus-tom designs tailored to ourcustomer’s requirements.

The highly vertically integratedstructure of the PI Groupallows control of each manu-facturing step, beginning at theraw material up to finishedNanoPositioning systems, in-cluding electronic drivers,amplifiers and controllers. Thiscomprehensive developmentand manufacturing know-howof electromechanical compo-nents and systems is unique inthe world.

The poling process in ferroelectric ceramics. Electric dipoles: (1) unpoled ferro-electric ceramic, (2) during and (3) after poling (piezoelectric ceramic).

PZT unit cell: 1) Perovskite-type lead zirconate titanate (PZT) unit cell in the symmetric cubic state above the Curie temperature. 2) Tetragonally distorted unit cell below the Curie temperature.

Applications for PiezoelectricActuators

■ Optics and Photonics

■ Precision Mechanics

■ Life Sciences, Medicine,

Biology

■ Vibration Cancellation

■ Adaptronics

■ Mechanical Engineering

■ Measuring Technologies

■ Microelectronics

■ Disk Drive

Since the piezoelectric effectexhibited by natural mono-crystalline materials such asquartz, tourmaline, Rochellesalt, etc. is very small, poly-crystalline piezoelectric cera-mic materials, such as lead(plumbum) zirconate titanate

(PZT), with improved proper-ties have been developed. PZT ceramics are available in many variations and are by far the most widelyused materials for piezo-electric actuator applicationstoday.

Piezoelectric Actuator Materials

Introduction


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Below the so called Curie tem-perature T

C(see Table 1) the

ionic lattice structure in thePZT crystallites becomes dis-torted and asymmetric (withan axis of polarity) and, addi-tionally, exhibits spontaneouspolarization. One result is thatthe discrete PZT crystallitesbecome piezoelectric. How-ever, the statistical distributionof the grain orientations in theceramic will cause the macro-scopic behavior to be non-piezoelectric.

An additional property, the fer-roelectric nature of the PZTmaterial, will help to solve thisproblem. When an intenseelectric field is applied to theceramic, the different latticeorientations of the individualceramic grains can be perma-nently altered. As a result ofthis “poling process” theceramic is accorded a netorientation of its internal, spon-

Piezoelectric Actuator Materials (cont.)

PIC 252

PIC 151 PIC 151 is a modified lead zirconate titanate (PZT)ceramic with high permittivity, coupling factorand charge constant. It is thus well-suited forPICA-Stack actuators and bender applications.Due to the high coupling factor and the low me-chanical quality factor it is also recommended forlow frequency and pulsed ultrasonic applications.

PIC 255 is a modified lead zirconate titanate (PZT)with a high Curie temperature, coupling factorand charge constant. The material is optimizedfor actuator application under dynamic or high-temperature working conditions. Because of itshigh coercive field, PIC 255 can be used for bipo-lar-driving-mode applications as well as for PICA-Shear actuators. Due to its high coupling effi-ciency, low mechanical quality factor and lowtemperature coefficient, it is also well-suited forlow-power ultrasonic transducers, non-resonantbroadband devices, sensors for load and soundtransducers and is preferred for vacuum applica-tions.

PIC 252 is a low-sintering modification ofPIC 255, especially used for multilayer actuators.

PIC 255

Table 1: PI Ceramic Standard PZT MaterialsParameter Unit PIC 151 PIC 155 PIC 255 PIC 181 PIC 241 PIC 300

Density � g/cm3 7.8 7.8 7.8 7.8 7.8 7.8

Curie Temperature TC

°C 250 345 350 330 270 370

Relative Dielectric Permittivity �33

T/�0

2400 1450 1750 1200 1500 1050

�11

T/�0

1980 1400 1650 1500 1550 950

Dielectric Dissipation Factor tan� 10-3 20 20 20 5 5 3

Electromechanical Coupling Factor kp

0.62 0.62 0.62 0.56 0.55 0.48

kt

0.53 0.48 0.46 0.46 0.43

k31

0.38 0.35 0.35 0.32 0.32 0.25

k33

0.69 0.69 0.69 0.66 0.64 0.46

k15

0.xx 0.63 0.63 0.32

Mechanical Quality Factor Qm 100 80 80 2000 1200 1400

Frequency Constant Np

Hzm 1950 1960 2000 2270 2190 2350

N1

Hzm 1500 1500 1420 1640 1590 1700

N3

Hzm 1750 1780 2010 1550 1700

Nt

Hzm 1950 1990 2000 2110 2140 2100

Piezoelectric Deformation d31

pm/V -210 -165 -180 -120 -130 -80

(Charge) Coefficient d33

pm/V 500 360 400 265 290 155

d15

pm/V 500 475 265 155

Piezoelectric Voltage Coefficient g31

10-3 Vm/N -11.5 -12.9 -11.3 -11.2 -9.8 -9.5

g33

10-3 Vm/N 22 27 25 25 21 16

Elastic Compliance Coefficient s11

E 10-12 m2/N 15.0 15.6 16.1 11.8 12.6 11.1

s33

E 10-12 m2/N 19.0 19.7 20.7 14.2 14.3 11.8

Elastic Stiffness Coefficient c33

D 1010 N/m2 10.0 11.1 xx 16.6 13.8 16.4

Temperature Coefficient TC�33

10-3/K 6 6 4 3 3 2

This data was measured according to EN50324 I/II.

taneous polarization in thedirection of the poling field andshows an overall piezoelectriceffect. For some PZT ceram-ics, it is necessary to performthe poling process at elevatedtemperatures.

Table 1 shows the specifica-tions of different PI CeramicPZT piezoelectric materials.

Ceramic types PIC 151 and PIC255 are the PI Ceramic stan-dard actuator materials whichare used for the PICA-Stackand PICA-Power actuators.These materials show thehighest piezoelectric deforma-tion constants, d

33, d

31and d

15

(see Table 1) and, conse-quently, the largest inducedstrain values at comparablefield strengths. These compo-sitions incorporate all our long-term experience in piezoelec-tric actuator development,manufacturing and applica-tion.


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Polymer coated stacked actuator (PICA-Stack) and ceramic insulated cofiredactuator (PICMA™).

Layers in a cofired monolithic piezo-electric actuator.

Layers in a stacked piezoelectricactuator.

PICMA™ and PICA:Cofired and StackedPiezoelectric Actuators Two main types of piezo actua-tors are available: cofiredPICMA™ actuators requiringabout 100 volts for full motion,and glued PICA-Stack actua-tors, requiring up to 1000 voltsfor full extension.The maximum electrical fieldwhich can be recommendedfor reliable operation of PZTceramics is on the order of 1 to2 kV/mm. To keep the operat-ing voltage within practical lim-its, actuators consist of thinlayers of electroactive ceramicmaterial which are electricallyconnected in parallel. The netpositive displacement is thesum of the displacements ofthe individual layers. The thick-ness of the individual layersdetermines the maximum ope-rating voltage of the actuator.

Glued PICA-Stack piezoelectricactuators consist of separateceramic discs with a thicknessof 0.2 to 1.0 mm. These val-ues, which are limited by themanufacturing technology, re-sult in nominal driving voltagesof up to 1000 V.

In contrast, PICMA™ actuatorsare manufactured using a cofir-ing technology. This advancedprocess allows for multilayerdesigns which have individuallayer thicknesses of just 20 to100 µm. Hence PICMA™ actu-ators require nominal voltagesof only 40 to 200 V.

Both types of piezoelectricactuators can be used formany applications: PICMA™actuators facilitate drive elec-tronics design and can be pro-duced at reasonable costs instandard sizes and large quan-tities. Due to its manufactur-ing technology, PICA-Stackactuators can be designedwith larger cross-sections forhigh-load applications. Theycan easily lift weights of up toseveral tons. Additionally, thePICA-Stack technology is veryflexible in terms of specialactuator shapes and sizes.

Comparison of a long-travel, high-loadpiezoelectric actuator and a compactactuator for small loads.


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For small electric driving sig-nals the displacement �L of abulk ceramic material samplecan be calculated from the fol-lowing equation:

(Equation 1)

�Lj= S

jL

0= d

ijE

iL

0

where:

Sj

mechanical strain in direction j (strain isdefined as relative length change,�L/L) [dimensionless]

L0

material thickness in field direction [m]

Ei

electrical field in direction i [V/m]

dij

piezoelectric deformation coefficient[pm/V]

Table 2 illustrates the differentpiezoelectric actuator displace-ment modes for PZT ceramics.

By convention, index 3 isalways aligned in the polingdirection of the material. Thesmall-signal values of the rele-vant piezoelectric deformationcoefficients d

33, d

31and d

15for

the different actuator materialscan be found in Table 1.

The longitudinal mode is usedfor most linear actuators in thiscatalog. In this mode, the elec-

tric field, the poling direction aswell as the mechanical strainor displacement, have thesame orientation. Keep in mindthat the longitudinal deforma-tion is always accompanied bya transverse deformation.When driven with a positivevoltage, U

3, the material

expands in the longitudinaldirection while at the sametime shrinking in the trans-verse direction, as can be seenfrom the material deformationfigures in Table 1. Whether the

Displacement Modes of Piezoelectric Actuators

Table 2: Piezoelectric actuator modes in PZT ceramics.Mode Material deformation Multilayer actuator configuration Remarks

Longitudinal The longitudinalmode is the mostimportant. It is used for PICMA™-,PICA-Stack-, PICA-Thru-, PICA-Power- and the Z-axis of PICA-Shear actua-tors.

Transverse This mode is usedfor standard bendingactuators (bimorphsor trimorphs) as well as for pure con-tractors and tubes.

Shear This mode is usedfor the X- and Y-axesof the PICA-Shearactuators.

relevant deformation coefficient: d33



actuator is of a longitudinal ortransverse type depends onlyon the displacement which isused. The shear mode is differ-ent, because in it the electricfield and the poling directionare perpendicular to eachother. The PICA-Shear actua-tors use the shear displace-ment in the poling direction.

To get the displacements ofthe individual layers in a multi-layer actuator to add whileusing the appropriate electricalcontact configuration, the pol-ing orientations of adjacent lay-ers have to alternate (seeTable 2).

Equation 1 is applicable forsmall electric signals only,because the piezoelectricdeformation coefficients, d

ij,

for PZT ceramics show strongelectric field dependency. Infact, the coefficient value canincrease by a factor of 1.5 to 2compared to the small-signalvalue in Table 1 when the nom-inal voltage of the actuator isapplied. This increase leads toa very high large-signal de-formation coefficient d

15of

1100 pm/V at an amplitude of250 V for PICA-Shear actua-tors, which are made ofPIC 255.

3

1

2

∆L

E3 PU

i

L0

+

-

3

1

2

∆L

E3 PU L0

i

+

-

∆L

E1P

U L0

1

3

2

i

+

-

L

∆L

E P

E P

E P

E P

E P

E PU

∆L

E P

E P

E P

E PU

∆L

U

E P

E P

E P

E P

E P

E P

where:

Ei

vector component of the electricfield

S polarization direction

U applied voltage

i current


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This narrow definition does not apply for PZT ceramicsbecause large- and small-signalconditions, static and dynamicoperation, open and shortedelectrodes must all be distin-guished. The poling process ofPZT ceramics leaves a rema-nent strain in the materialwhich depends on the magni-tude of polarization. The polar-ization is affected by both thedrive voltage and externalforces. When an external forceis applied to poled PZT ceram-ics, the dimensional changedepends on the stiffness ofthe ceramic material and thechange of the remanent strain(caused by the polarizationchange). The equation L

N= F/k

T

is only valid for small forcesand small signal conditions.For larger forces, an additionalterm describing the influenceof the polarization changes,must be superimposed onstiffness (k

T).

Quasi-static characteristic mechanical stress/strain curves for piezoceramic actuators and the derived stiffness values (note that displacement is negative because the applied force is compressive). Curve 1 is with the nominal operating voltage (voltage giving nominalmaximum displacement) on the electrodes, Curve 2 is with the elec-trodes shorted (showing ceramics after depolarization).

StiffnessSince PZT ceramics are activematerials, they produce anelectrical response (charge)when mechanically stressed(e.g. in dynamic operation).When the electric charge can-not be drained from the ceram-ics, it generates a counterforceto the mechanical stress. Thisis why a piezoelectric ceramicwith open electrodes appearsstiffer than one with shortedelectrodes. With actuators(compound structures of dif-ferent active and passivematerials) the scenario is evenmore complicated.

The above discussion explainswhy the (dynamically meas-ured) resonant frequency of apiezo actuator differs from thestatically measured stiffnessusing the equation

(Equation 2)

f0= 12�

___��k T

meff

___

Since stiffness values of piezoactuators are not constantsthey can only be used to esti-mate the behavior under cer-tain conditions and to comparedifferent piezoelectric actua-tors of one manufacturer.

Mechanical Considerations

When calculating force genera-tion, resonant frequency, sys-tem response, etc., piezo stiff-ness is an important parame-ter. In solid bodies stiffnessdepends on the Young’s modu-lus, the ratio of stress (forceper unit area) to strain (changein length per unit length). It isgenerally described by thespring constant k

T, relating the

influence of an external forceto the dimensional change ofthe body.


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PI Ceramic actuators can withstand high pushing forcesand carry loads to several tons. Even when loaded, theactuator will not lose any travelas long as the maximum loadcapacity is not exceeded. Loadcapacity and force generationmust be distinguished.

Mechanical Considerations . . . (cont.)

Load CapacityLike any other actuator, apiezoelectric actuator is com-pressed when a force isapplied. Two cases must beconsidered when operatingpiezoelectric actuators with aload:

a) The load remains constantduring the motion process.

b) The load changes during themotion process.

Changing Force

(Force = Function of �L, e.g. aspring load):

{bk xtx4261}

Displacement is reduced{bk xtx4262}

For PZT operation with springloads different rules apply. The“spring” could be an I-beamor a single fiber, each with itscharacteristic stiffness orspring constant. Part of thedisplacement ge-nerated by thepiezo effect is lostdue to the elastic-ity of the piezoelement. The totalavailable displace-ment can berelated to thespring stiffnessby the followingequations:

(Equation 3)

�L � �L0( kT

kT+ kS

______)Maximum displacement of apiezo actuator acting against aspring load.

bConstant Force

Zero point is offset

A mass is installed on the actuator whichapplies a force F = M · g (M: mass, g:acceleration due togravity). With constantforce the zero pointwill be offset by anamount �L

N� F/k

T,

where kT

equals thestiffness of the PZTactuator. If this force

is within the specified loadlimit (see technical data table),full displacement can beobtained at full operating volt-age.

M

a

Case a,zero-point offset with constant force (mass).

(Equation 4)

�LR

� �L0 (1- kT

kT+kS

______)Maximum loss of displace-ment due to external springforce. In the case where thespring stiffness k

sis � (infi-

nitely rigid restraint) the PZTonly acts as a force generator.

Case b, effective displacement of a piezoactuator acting against a springload.


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Force generation vs. displacement of a piezo actuator (displacement 30 µm, stiffness 200 N/µm) at various operating voltages. The points where the dashedlines (external spring curves) intersect the actuator force/displacement curves determine the force and displacement for a given setup with an external spring.Maximum work can be done when the stiffness of the actuator and external spring are identical.

In most applications, PZT actu-ators are used to produce dis-placement. If used in arestraint, they can generateforces. Force generation isalways coupled with a reduc-tion in displacement. The max-imum force (blocked force) apiezo actuator can generatedepends on its stiffness andmaximum displacement.

(Equation 5)

Fmax

� kT��L

0

Maximum force that can begenerated in an infinitely rigidrestraint (infinite spring con-stant). At maximum force gen-eration, displacement is zero

where:

�L0

= max. nominal displacement with-out external force or restraint [m]

kT

= PZT actuator stiffness [N/m]

In actual applications the loadspring constant can be largeror smaller than the actuatorspring constant. The force F

max effgenerated by the actua-

tor working against an elasticrestraint is:

{bk xtx4239}

(Equation 6)

Fmax eff

� kT��L

0 (1- kT

kT+kS

_____)Effective force a piezo actuatorcan generate in a yieldingrestraint

where:

�L0= displacement (without external force

or restraint) [m]

kT

= PZT actuator stiffness [N/m]

ks

= stiffness of external spring [N/m]

Force Generation


How Fast Can a PiezoActuator Expand?

Fast response is one of thedesirable features of piezoactuators. A rapid drive-voltagechange results in a rapid posi-tion change. This property isnecessary in applications suchas switching of valves/shut-ters, generation of shock-waves, vibration cancellationsystems, etc. A piezo actuatorcan reach its nominal displace-ment in approximately 1/3 ofthe period of the resonant fre-quency.

(Equation 7)

Tmin

� 1___3f0

Rise times on the order ofmicroseconds and accelera-tions of more than 10,000 g’sare possible.

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Response of an undamped, lever-amplified PZT actuator (low resonant frequency)to a rapid drive-voltage change. Driving techniques such as InputShaping®

eliminate self generated ringing and allow settling in one period of the resonantfrequency.

Effective mass of an actuator fixed at one end.

Dynamic Behavior

Resonant Frequency

Piezoelectric actuators are notdesigned to be driven at reso-nant frequency at the nominalvoltage and load. This willresult in high dynamic forceswhich might damage the struc-tural integrity of the ceramicmaterial (see Handling Pre-cautions p. 42).

In general, the resonant fre-quency of any spring/masssystem is a function of its stiff-ness and effective mass. Theresonant frequency given inthe technical data tablesalways refers to the unloadedactuators .

(Equation 8)

f0= ( 1___

2�)��kT_______meff

Resonant frequency of an idealspring/mass system

where:

f0

= resonant frequency [Hz]

kT

= actuator stiffness [N/m]

meff

= effective mass (about 1/3 of themass of the ceramic stack plus anyinstalled end pieces) [kg]

Resonant frequencies of in-dustrial-reliability piezoelec-tric actuators range from100 kHz for actuators with atotal travel of a few microns toa few kilohertz for actuatorswith a travel of more than100 microns.

For more information on

advanced driving tech-

niques such as Input-

Shaping, Preshaping, and

Dynamic Linearization,

see the PI NanoPosition-

ing Catalog, or website

www.pi.ws.


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Piezoelectric actuators operateas capacitive loads. The leak-age current values of PICeramic actuators are verylow, because the effectivelarge-signal volume resistivityof the materials used is verylarge. Therefore, the actuatorsconsume almost no energy instatic applications and conse-quently they produce virtuallyno heat.

In dynamic applications, thepower consumption increaseslinearly with the frequency and the actuator capacitance.Note that actuator capacitancevaries with respect to theapplied voltage.

Close contact with the manu-

facturer will assure that

the right actuator design is

chosen for your application!

Hysteresis and Creep

The displacement hysteresisand creep in piezoelectric actu-ators can either be completelyeliminated by closed-loopoperation, or significantlyreduced by advanced open-loop driving techniques. Open-loop piezoelectric actuatorsexhibit hysteresis in theirdielectric and electromechani-cal large signal-characteristics.This hysteresis is mainlycaused by microscopic ferro-electric polarization effects andis thus inherent to the materi-als used.

Hysteresis increases with theelectric field or voltage ampli-tude with which the actuator isdriven. The “split” in the volt-age-displacement curves (seefigure “Hysteresis curves”)typically starts at 2% for verysmall signals and reaches its

maximum on the order of 10%to 15% at nominal voltage. Forshear actuators these valuescan be even higher.

The same material mecha-nisms responsible for hystere-sis are responsible for thecreep phenomena in piezo-electric actuators. Driven by astep signal, the actuator willfollow the increasing voltageamplitude very closely, but itwill continue to change indimension slowly afterwards.The creep rate decreases loga-rithmically with time. The over-all behavior is described by thefollowing equation:

(Equation 9)

�L(t) � �Lt=0.1[1+�lg( t___

0.1)]where:

�L(t) ... displacement as a function oftime [m]

�Lt=0.1

... displacement at 0.1 secondsafter the voltage step is com-plete [m]

... creep factor, dependent on theproperties of the actuator (onthe order of 0.01 to 0.02)

Again, the creep of the actua-tor can be completely elimi-nated by closed-loop opera-tion.

Actuator Self-Heating

When a piezoelectric actuatoris driven by an AC voltage, theapparent electric power con-sists primarily of reactivepower, because of the capaci-tive nature of the actuator.Even for small electric signals,however, the dielectric lossfactor, tan �—the relationbetween true power and reac-tive power—is on the order of2% for actuators made of PZTceramics. When the signalincreases up to the peak-to-peak value corresponding to

the nominal voltage, the lossfactor becomes larger as well.It can increase up to 12% to15% for longitudinal actuatorsor even more for shear actua-tors. The dielectric loss isclosely related to the hystersis.When considering the accom-panying quadratic increase ofthe power with the field, and,additionally, the increase inactuator capacitance with fieldby a factor of 1.5 to 2, self-heating effects can becomesignificant during cycling withhigher repetition rates athigher fields. Besides alteringthe performance specifica-tions, this self-heating effectcan possibly destroy the actua-tor, should the temperatureincrease above the allowedmaximum.

Because the actual maximumtemperature increase insidethe actuator depends on sev-eral factors like thermal cou-pling of the actuator to itsmechanical environment, thegeometry of the actuator itself,or whether it is driven withforced convection or not, thereis no general rule for thedriving power of a specificactuator.

Close contact with the man-

ufacturer will help you to

find a reliable solution for

your application problem.

Creep of open-loop motion after a 60 µmchange in length as a function of time. Creep is on the order of 1% of the last commanded motion per time decade.

Hysteresis curves of an open-loop piezo actuator for various peak voltages. The hysteresis is related to the distancemoved.

Driving Piezoelectric Actuators


48


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Open- and Closed-Loop Operation

For more information on

advanced driving tech-

niques, closed-loop oper-

ation, controllers and

nanopositioning sensors,

see the PI NanoPosition-

ing Catalog, or website

www.pi.ws.

Response of a PICA Stack piezo translator to a ± 1V, 200 Hz triangular drive signal. Note that one division is only 2 nanometers.

Piezoelectric actuators can beoperated in open-loop andclosed-loop modes. In open-loop, displacement roughlycorresponds to the drive volt-age. This mode is ideal whenthe absolute position accuracyis not critical. Open-loop piezo-electric actuators exhibit hys-teresis and creep behavior, likeother open-loop positioningsystems.

Position servo-control elimi-nates nonlinear behavior ofPZT ceramics and is the key tohighly repeatable motion.

PI offers the largest selectionof closed-loop piezo mecha-nisms and control electronicsworldwide. The advantages ofposition servo-control are:

■ Very good linearity, stability, repeatability and accuracy

■ Automatic compensationfor varying loads or forces

■ Virtually infinite stiffness(within load limits)

■ Elimination of hysteresisand creep effects

Piezoelectric actuators have no“stick slip” effect and there-fore offer theoretically un-limited resolution. In practice,actual resolution can be limitedby a number of factors such asdriving amplifier noise, sensorand control electronics quality,which may exhibit noise andsensitivity to EMI, as well asmechanical parameters suchas mounting precision, preload-ing, guiding and mechanicalamplification mechanisms.

Ctrl Input /V

Open-loop vs. closed-loop performance graph of a typical PI PZT actuator (supplied with each closed-loop system).


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The lifetime of a piezoelectricactuator is not limited by wearand tear. All PI Ceramic piezoactuators are specificallydesigned for high-duty-cycleapplications. All materials usedare matched for robustnessand lifetime. Endurance testson PI Ceramic actuators proveconsistent performance, even

Lifetime of PI Ceramic

Piezoelectric Actuators

after billions (1,000,000,000) ofcycles. There is no genericequation to determine the lifetime because of the many parameters such as temperature, humidity, volt-age, acceleration, load, operat-ing frequency, insulation materials, etc. which have aninfluence.

PICMA™-type actuators haveadvantages over other piezoactuators, especially in humidenvironments. Their mono-lithic, ceramic-insulated designblocks the diffusion of watermolecules into the insulationlayer, the major cause ofdielectric breakdown.

PI Ceramic invests consider-able energy in investigatingand continually improving actu-ator lifetime. The design of thepiezoelectric actuators in thiscatalog reflect several decadesof experience in with thou-sands of industrial piezo actua-tor applications. Another resultof this experience is the“Handling Precautions” in thefollowing section.

PICMA™ piezo actuators (bottom curve) compared with conventional multilayeractuators with polymer insulation (top curve). PICMA™ Actuators are not affectedby the high-humidity test conditions. Conventional piezo actuators exhibit in-creased leakage current after only a few hours. Leakage current is an indication of insulation quality and expected lifetime. Test conditions: U = 100 V

DC ; T = 25 °C;

Relative Humidity = 70%

Please contact your PI

sales & application engi-

neer for further infor-

mation on lifetime and

handling issues.


50


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No pulling force without preload.

No lateral force or torque.

Ball tips or flexures to decouple lateral forces or bendingforces.

Handling Precautions

Piezoelectric actuators mustbe handled with care becausethe internal ceramic materialsas well as ceramic end-platesare fragile. Do not use metaltools for actuator handling. Donot scratch the coating on theside surfaces.

Besides these general instruc-tions the following precautionshave to be considered duringhandling of PI Ceramic piezo-electric actuators:

1. Piezoelectric stack actuatorswithout axial preload aresensitive to pulling forces. A preload of half of theblocking force is generallyrecommended (see datatables p. 13 to p. 27). Thisrecommendation is alsovalid for PICA-Shear actua-tors in axial direction, per-pendicular to the sheardiplacement directions.

2. Piezoelectric stack actuatorsmay be stressed in the axialdirection only. The appliedforce must be centered verywell. Tilting and shearingforces, which can alsobe induced by parallelismerrors of the endplates,have to be avoided because

they will damage the actua-tor. This can be ensured by the use of ball tips, fle-xible tips, adequate guidingmechanisms etc. An excep-tion to this requirement ismade for the PICA-Shearactuators, because theyoperate in the shear direc-tion. Do not exceed themaximum shear force spe-cifications for these actua-tors.

3. Piezoelectric stack actuatorshave to be mounted by glu-ing them between evenmetal or ceramic surfacesby a cold or hot curingepoxy, respectively. Groundsurfaces are preferred.Please, do not exceed thespecified working tempera-ture range of the actuatorduring curing.

4. The environment of all actu-ators should be as dry aspossible. While PICMA™actuators are guardedagainst humidity by theirceramic coating, other actu-ators must be protected byother measures (hermeticsealing, dry air flow, etc).

Lifetime of PI Ceramic

Piezoelectric Actuators . . . (cont.)


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Bolting between plates is not recommended.

The combination of long-term high electric DC fields and high relative humidityvalues should be avoidedwith all piezoelectric ac-tuators. The electric fieldattracts the water mole-cules or hydroxy ions fromthe environment to the sur-face of the stack and leadsto a permanent increase inits leakage current. This canfinally result in damage to the actuator. There is nopolymer coating which canavoid the forced penetrationof these molecules.

5. It is important to short-circuit the piezoelectricstack actuators during anyhandling operation. Theresulting loads will inducecharges on the stack elec-trodes which might result inhigh electric fields if theleads are not shorted:

a) changing temperatures,for example during curingor soldering processes,induces charges by thepyroelectric effect

b) changing mechanicalloads, for example duringpreload application, in-duces charges by thedirect piezoelectric effect

5. Should the stack becomecharged, rapid discharging—especially without a pre-load—might damage thestack. Therefore, it is appro-priate to use a resistor for dis-charging after any mistreat-ment. PI Ceramic deliversPICA-Stack piezoelectric ac-tuators with a shorting clamp.We recommend use ofgloves and safety glassesduring handling.

6. The lateral (side) surfaces ofPICMA™ and PICA-Stackactuators are not, or not fully,electrically insulated to allowa more compact design andintegration of the stack in the final assembly by the customer. Therefore, the customer is responsible fordesigning in the required se-paration or suitable insulatingmaterials, like polyamide foilor PTFE tape, to insulate thestack from its surrounding.

7. Prevent any contamination of the stack surfaces withconductive or corrosive sub-stances. Cleaning of thestacks should be done withIsopropanol only. Do not useacetone. Avoid excessiveultrasonic cleaning at highertemperatures.

k fr}Ball tips or flexures to decouple bending forces.


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Applications

■ Actuators

■ Sensors

■ Ultrasonic Transducers

■ Sonar Technology

■ Ultrasonic Cleaning and

Welding

Piezoelectric Components

mm

Discs OD 1 - 80

Thickness min 0.2

Rings OD/ID 3 - 50

Thickness 0.2 - 15

Tubes OD/ID 1 - 80

L max. 50

Plates L/W 1 - 70

TH min 0.2

Shear Plates L/W 2 - 20

Thickness max. 15


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Applications

■ NanoPositioning

■ High-Load Positioning

■ Active Vibration

Cancellation

■ Smart Structures


■ Chip Manufacturing and

Testing

■ Laser Tuning

see PICA-Stack, PICA-Power andPICA-Thru datasheets, pages 16, 18, 20

PICA-Stack Piezoelectric Actuators

PZT Actuator for Structural Deformation / Vibration Damping in Aerospace Applications.

Technical DataDisplacement up to 300 µm

Blocking force up to 80 kN

Static load up to 100 kN

Operating voltage range 0 to1000 V

Operating temperature range -20 to +85 °C (cryogenic and up to +150 °C on request)

Dynamic reliability more than 109 cycles

Cross section shapes cylindrical, tubular, rectangular

Length up to 300 mm

Variety of piezo ceramic stacks.


Special Features

■ Low Operating Voltage

■ No Polymer Coating

■ Ceramic Insulation

■ 100% Ultra-High Vacuum

Compatible

■ Sub-nm Resolution

■ Sub-ms Response Time

Applications

■ NanoPositioning


■ Semiconductor

Equipment

■ Valves

■ Laser Applications

■ Telecommunication

see PICMA™ datasheets pages 13, 14, 15

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PICMA™ Monolithic Multilayer Actuators

Technical DataCross section 2x2 to 10x10 mm2

Displacement up to 30 µm / segment

Blocking force up to 5 kN

Operating voltage max. 120 V

Operating temperature - 40 to +150 °C

PICMA™ Monolithic Actuators are the only ceramic insulated piezo actuatorsavailable. They provide higher reliability than other monolithic actuators and exhibitno measurable outgassing.


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Special Features


■ Special Polymer

Insulation

■ 100% UHV Compatible

■ Sub-nm Resolution

■ Sub-ms Response Time

Applications

■ NanoPositioning

■ Piezo-Motors

■ Semiconductor

Equipment

■ Laser Applications

see PICA Shear Actuators datasheet,page 22

PICA-Shear Actuators (X, XY and XYZ)

Technical DataCross section 3x3 to 10x10 mm2

Displacement up to 10 µm

Operating voltage max. +/- 375 V

Operating temperature -40 to +150 °C (cryogenic on request)


Applications

■ Micropositioning

■ Pneumatic Valve Control

■ Telecommunication

■ Optical Switches

■ Ink Jet Printers

Special Features


■ No Polymer Coating

■ Full Ceramic Actuator

■ 100% UHV Compatible

■ µm Resolution

■ ms Response Time

see PICMA™ Bender datasheet, page 24

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Piezoelectric Bender Actuators

Technical DataDisplacement up to 2 mm

Blocking force up to 2.5 N

Operating voltage max. 60 V / 300 V

PI Ceramic Multilayer Benders are excellent actuators for pneumatic valves.

Variety of custom benders.


GERMANY

PI Ceramic GmbH

Lindenstrasse07589 LederhoseGermanyTel: +49 (36604) 882-0Fax: +49 (36604) 882-25Email: [email protected]://www.piceramic.com

Physik Instrumente (PI)

GmbH & Co.Auf der Römerstrasse 176228 KarlsruheTel: +49 (721) 4846-0Fax: +49 (721) 4846-299Email: [email protected]://www.pi.ws


Piezo Ceramic Actuators& Custom Subassembliesfor Capital EquipmentApplications & Research


USA

PI Physik Instrumente) L.P.Email: [email protected]://www.pi-usa.usUSA East (Canada)

Tel: +1 (508) 832-3456Fax: +1 (508) 832-0506USA West (Mexico)

Tel: +1 (714) 850-9305Fax: +1 (714) 850-9307

JAPAN

PI-Polytec Co. Ltd.Email: [email protected]: +81 (42) 526 7300Fax: +81 (42) 526 7301

UK

Lambda Photometrics Ltd.Tel: +44 (1582) 76 43 34Fax: +44 (1582) 71 20 84Email: [email protected]://www.lambdaphoto.co.uk

FRANCE

Polytec PI S.A.Tel: +33 (1) 48 10 39 30Fax: +33 (1) 48 10 08 03Email: [email protected]://www.polytec-pi.fr

ITALY

Physik Instrumente (PI) S. r. l.Tel: +39 (02) 665 011 01Fax: +39 (02) 665 014 56Email: [email protected]://www.pionline.it

piezo ceramic actuators & custom subassemblies

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