Low voltage co-fired multilayer
stacks, rings and chips for actuation(without casing)Low voltage actuators with casings, high voltage actuators

Check main catalogue

contents

1.

State of the art of co-fired low voltage actuators

3

1.1

Piezo-stacks with on-stack-insulation (osi)5

1.2

Piezo-stacks with in-stack-insulation (isi)72.

Aspects of actuator operation

11

2.1

Bulk-stacks or hollow ring-stacks

11

2.2

Mechanics of actuator operation

12

2.3

Mounting advises

14

2.4

Influences from ambient

17

2.5

Electrical operation conditions

18

3.

Products, technical data

20

3.1

Piezo-stacks PSt 150 / HPSt 150 (osi-type)

21

3.2

Piezostacks PSt 150 hTc with reduced capacitance (osi-type)

24

3.3

Piezo-chips PCh 150 / HPCh 150 (isi-type)

3.4

2(with buried electrode design)

26

Special designed stacks and rings

28

State ofStandderthe art of co-fired
Piezo-Multilayer-Techniklowvoltage actuators

1

Piezo actuators are electro-mechanical “motors”, based on the solid state piezomechanical deformation effect of piezo-ceramics (PZT lead [“plumb”] zirconium
titanate). Highlights are unlimited positioning sensitivity (sub-nanometers), high load
capability and high force generation resulting in utmost mechanical dynamics withreaction times down to micro seconds. Only piezo actuation allows top innovations
in mechatronics like nano-positioning or high pressure common rail fuel injection.

Fig. 1: Variety of different kinds of low voltage piezo-elements

Since more than 20 years so-called co-fired multilayered piezo-elements are available for low voltage
piezo-actuation. The trick is to pile up thealternating ceramic / electrode layers structure in the“green” = soft state of the ceramics and to apply
afterwards the high temperature sintering process
to get the finished ceramic stack.
Special design steps are needed to get theelectrically insulated “capacitor”-structure ofactuator stacks and rings.
Two concepts have been developed and are in use
since a long time, the “on-stack-insulation”-

technique (osi) and the “in-stack-insulation”technique (isi). Even when these techniques
seemingly aim only for the electrical configuration of
the stacks, there are significant mechanicalconsequences to performance and reliability of thestructure due to the electro-mechanical coupling via
the piezo-electric effect. The osi-structure exhibit
remarkably advantages in actuator performance andease of handling compared with other techniques.
In terms of quantity and diversity of applications theosi-stacks have the widest distribution at the
moment due to their robust and general purpose31. State of the art of co-fired low voltage actuators

character. Osi-actuators are preferentially used at
operating temperatures < 100 °C.
Since a few years, the ultra-fast injection valve
actuation (“piezo-injectors”) by piezo-stacks gavean additional push to the industrial application of
co-fired piezo-elements. Reliable operation attemperatures up to 150 °C is a self-evident must.

4

Special piezo-stacks have been developed using
the isi-stack design together with a special highstrain / high temperature PZT-ceramics.
These injector elements are optimized to run in akind of switching mode with rise-times < 100 µsec
and cycle numbers up to 1010. The development of
this technology started in Southern Bavaria /Germany.

1
1.1 Piezo-stacks with on-stack-insulation (osi)Among the spectrum of low voltage multilayer actuators, the osi-based elements
have found the widest applications. The patent for this technology has expired sincea few years. The main step is to use a fine glass filament fused onto the PZT-ceramic
stack, where the internal layer electrode comes to surface and shall be separated
electrically from the counter-polar supply electrode. The glass filaments are well
separated from each other and do not form a dense (inflexible) glass layer (Fig. 2).
●
100%
internal electrodeDue to the absence of structure borne tensilestress within the ceramics, the osi-stacks can be
operated with high strain rates without
mechanical preload (as long as no externaltensile forces are present).

Surface protection
The sidefaces of standard osi-stacks are coated bypolymers.

PZT-layers

glass insulation
supply electrodeThe coating protects the brittle ceramics against“less” skilful handling, mechanical attack or
chemical contamination.

Fig. 2: Schematic of the osi-technique using fused-on glass
fibers to terminate internal electrodes on stack’s surface

The main highlights of the osi-technique are
100% active PZT-ceramic cross-section andstack volume for maximum stroke and force
generation (blocking force).

●●

Homogeneous strain within the PZT-volume,no intrinsic mechanical tensile stress by active /inactive PZT-boundaries resulting in ceramic
cracking and electrical break down.

●

The absence if intrinsic inhomogeneous stressresults in low tilting of the actuator endfaces(useful for coherent-optical arrangements of ringactuators).

●

High electrical reliability:
Osi-actuators show a dense PZT-ceramic surface
without side cuts or slots as the isi-techniquedoes. No risk of rupturing the supply electrodes
at slots / cuts within the side-faces of the stack.

Fig. 3: Different kinds of stack coatingsSpecial coatings are available to handle exotic
driving conditions like cryogenic temperatures,vacuum / UHV, immersion in (non-aqueous) liquids
Polymers are much more flexible than PZT-ceramics
and do therefore not affect adversely the piezoaction.

51.1 Piezo-stacks with on-stack-insulation (osi)On the contrary: A thicker coating acts as a kind of
reinforcement and “ruggedizing”, making the stacks
less sensitive to bending or tilting forces than an
uncoated ceramic stack (Fig. 4).
F
piezo-stack

A piezo-stack PSt 150 / 2 x 3 / 20 with a ceramiccross-section of 2 x 3 mm has been bended bya force F (distance D of the supporting points:
15 mm, bended stack’s dimension: 2 mm).
The coated ceramic stack withstands a force F of
80 Newtons before breaking, whereas the uncoatedstack can bear only 38 Newtons!
Standard coated stacks show a better resistance toa less skilful handling or sub-optimum mechanicaldesigns. Bending oscillations of longer stacks witha critical ratio of length / cross-section are damped
away.

D

Fig. 4: Schematic of a bending experiment

6

Osi-Technology is used by PIEZMECHANIK forthe piezo-stacks and rings PSt 150 / HPSt 150.

1.2 Piezo-stacks with in-stack-insulation (isi)The isi-piezo-stack design is a more simple insulating strategy, well-known since
the early days of low voltage actuation in the 70ies of the past century.
The necessary electrical insulation step is done inside the stack: The PZT-layers
are not completely metallized. A small insulation gap ensures the electricalseparation between the internal electrode and the external supply electrode (Fig. 6).

Fig. 5: Isi-actuators in different Execution

internal
electrodeinsulation gap(no internal electroding

It is easily seen, that the PZT-ceramic of the stack isonly partially active and a steep transition from
active to inactive PZT-ceramic is created:
A pronounced mechanical tensile stress at theactive / inactive boundary region occurs, when the
PZT-stack is activated and expanding (Fig. 7).

supplyelectrodeFig. 6: In stack insulation scheme.
71.2 Piezo-stacks with in-stack-insulation (isi)internal
electrodeinsulation
gap

active / inactive boundary region
with tensile stress spots

A Limitation of thickness of the monolithic multilayer package.
No cracking of the ceramic occurs for rather thinelements. This means: When the axial thicknessof the multi-layer element is held within 2-3 mm(“Piezo-chips”).
Longer stacks are manufactured by gluing ofsuch monolithic piezo-chips (Fig. 8). The gluelines between the chips provide stress relaxation.
The mechanical properties of such stacks longer
stacks depend to some extent on the quality of
the glue-joints.

Fig. 7: Mechanical stress generation inside a isi-piezostack at
the active / inactive boundary

This leads potentially to mechanical cracking of theceramic and electrical break down of the stackduring long-term action, when potential crack
propagation is not compensated for by special
techniques.

Fig. 8: Chip-based piezo-stack8

1.2 Piezo-stacks with in-stack-insulation (isi)

B Stress reduction by expansion joints
For producing monolithic multilayer-stacks withlengths > 3 mm, slots are prepared into theceramic parallel to the PZT-layers in the criticalactive / inactive ceramic section (Fig. 9).

internal
electrodeactivePZT
volumeside cuts / slots

supply electrodeC Mechanical preloading
In addition to the above-mentioned techniques,
the internal stress-problem of isi-actuators is
usually handled by the application of a large axial
preload or prestress even for static or low dynamic applications.
D Rupturing of supply electrodes
The supply electrodes of isi-structures must bridge the side slots/cuts in the stack structure. For
simple arrangements, the side electrodes tend to
rupture in the vicinity of the side slots, when thestacks are operated with high strain and dynamics. The actuator will be deactivated then.
The optimum of highly reliable side electrodes isachieved by using metal mesh.
(The osi-techniques does not need such strategies simply due to the absence of the side
cuts/slots).

Fig. 9: Isi-based stack with stress relaxation side slots

The isi-structure with side slots is more sensitive tobending forces, because the notches act as starting
point of ceramic cracking (Fig. 10).

F
piezo-stack

onset of crack
propagation
at side slots

D

Fig. 10: Bending-induced ceramic cracking of isi-stacks withside slots

The designs of any coupled mechanics has to be
optimized for strict axial loading of isi-stacks.
Attention should be paid to any mechanicalinfluences resulting in bending modes especially ofstacks with large ratio of length / diameter.
91.2 Piezo-stacks with in-stack-insulation (isi)Surface protection techniques, buried electrodedesign.
Isi-stacks can by coated with polymers for surface
protection in a similar way as described for theosi-systems.
An alternative is the buried electrode design wellknown since the early days of low voltage
actuation: Nearly te complete circumference of the
PZT-stack’s cross-section is kept free of any
metallization (except the small contact section
towards the supply electrode) (Fig. 11).
By burying the internal electrode no additional
coating is needed to prevent electro-corrosion when
the stack comes to a contact with contaminants.
But this is to the cost of an additional reduction of
the active PZT-cross-section together with anextension of the inactive / active PZT-boundary
problem.

10

insulatedcircumference
active area

supplyelectrodeFig. 11: “Buried electrode” scheme

2

Aspects ofactuator operation
2.1 Bulk-stacks or hollow ring-stacks

Ring-actuators are stacks with a centre-bore. It is self-evident, that such a design
allows smart and elegant design solutions, when the centre axis of a piezo systems
shall be accessible for mechanical, electrical, optical or other purposes.

ExampleA massive stack actuator PSt 150 / 7 x 7 / 20 shows asimilar piezo-ceramic volume like the ring-actuator
HPSt 150 / 14-10 /12.
For identical electrical driving conditions, the power
consumption and energy dissipation is the same.
It has been evaluated, under what cycling frequency
both kinds of actuators heat up to 80 °C, whenrunning in ambient air at room temperature.
ResultStack-actuator PSt 150 / 7 x 7/ 20:
240 HzRing-actuator HPSt 150 /14 -10 /12: 440 Hz
Fig. 12: Massive stack actuator and hollow cylindricalring-actuator

Beside these design aspects, the use of rings has
distinct piezo-mechanical operation advantages
compared to solid stacks: Assuming the same
piezo-ceramic volume (defined by equal active
ceramic cross-section and length) for a stack and aring-actuator under comparison, the electrical
capacitances and power consumption are thesame.

The ring-actuator shows remarkable advantages inheat management due to the larger specific surface.
By forced cooling / heat-sinking / immersion incooling liquids, ring-actuators can run full stroke up
to the kilohertz range.

ring-actuatorheatsink
heattransfermedium

But a ring-actuator shows a●higher bending stiffness due to the increased
actuator diameter● lower self-heating temperature level, when operated dynamically.
The ring-actuator shows a larger surface (inner andouter circumference) for a better heat transfer to air.

Fig. 13: Scheme of highly efficient ring-actuator cooling by
inner and outer heat-sinking

112.2 Mechanics of actuator operation

The handling of piezo-actuators during mounting and operation is ruled by the
specific mechanical properties of ceramics like brittleness, low tensile stressdamage threshold on one side and its sensitive electrical structure on the otherside.

Stack type actuators are mechanically coupled
only via the end faces e.g. by clamping, gluing orother methods. The end-faces are electricallyinsulated, so metal parts can be coupled directly
to the stack.
No mechanical contact / impact shall be applied
to the side faces.
The side faces bear the supply-electrodes tocontact electrically the internal layer electrodesof the capacitor structure. The supply electrodes
are wired by pig-tails near the actuator socket.
Standard actuators PSt 150 are finally coatedwith a high quality polymer and are therefore
more resistant to mechanical and otherinfluences than bare ceramic components.

sensitive side !
no mechanical contact !
mounting side

sensitive side !
no mechanical contact !

Fig. 14: Mounting scheme of piezo-actuators

12

Piezo-stacks can bear high compressive load
forces, but they are very sensitive to bending-,
torsion-, shear-forces and especially to tensile
forces. Attention has to be paid to this fact not only
during the final operation of such stacks, but during
all handling and mounting steps in advance tooperation.
The design of any attached mechanics shall aim forpure axial loading of the actuators without any
compromise. Imperfect solutions can lead tostrongly reduced performance and reliability.
Pay attention not only to the static force balances,
but also to dynamic influences (acceleration forces
resulting in bending motion or torque).

2.2 Mechanics of actuator operation

Mechanical preloading:
Preloading is achieved in most cases by using anelastic spring for resetting the moving part of an
actuator.
Mechanical preloading of piezo ceramics isnecessary to allow a push-pull-operation of an
actuator. This is to handle externally applied tensile
forces caused by static or dynamic driving
conditions. With isi-type actuators, preloading
compensates further for intrinsic tensile stressphenomena as described in section 1.2.
A properly designed mechanical preloading ofactuators reduces further microscopic tilting of theactuator end-faces. Coherent optical arrangements
like tuneable etalons / resonator structures do notneed then additional guiding mechanism for shifts inthe micro-meter range.

Operating stack actuators with reduced strain
Regarding stroke, a beginner in piezo actuation
usually seeks for an actuator type, what’s maximum
rating stroke covers rather exactly the needed
range. This implies consequently, that this actuators
is operated up to maximum voltage, maximum
electrical field strength, maximum strain andthereby for dynamic applications with maximum
power consumption and power losses.
The use of an “oversized” longer actuator can havea lot of advantages compared to the above
mentioned “maximum ratings” operation:● The long-term reliability is improved by the use of

reduced electrical field strength (driving voltage<< max. voltage rating).
●

The reduced mechanical strain results in a lower
power consumption and self-heating.
Vice versa higher oscillation frequencies can beachieved by applying the same power as with the
maximum rating type actuators.

●

Power supplies with reduced output voltages canbe used, providing higher currents (=> higher
actuator oscillation frequency) and lower costs.

moving top

preload spring

piezo-stack

This reduced strain strategy finds its limits, whenhigher resonance frequencies, stiffness are a mustor the stack length is restricted by space limitation.

Fig. 15: Schematic of a preload spring mechanism

Preload forces can be high as 50% of the load
capability of actuators or even more, to handle
extreme driving conditions (e.g. pulsed operation or symmetrical push-pull arrangements).
The “golden rule” of preloading:Use preload springs of lowest possible stiffness(large compliance).
A good attempt is to select for a spring’s
stiffness in the % range of actuator’s stiffness.
Then, no loss of stroke will occur even whenhigh preload forces are applied.
(details: See “force generation” in main catalogue)

132.3 Mounting advises

The achievable performance and reliability of an actuator must be seen always incontext with the interaction with the operated mechanical system and the electricaldriving characteristics.

Poorly designed mechanics like low stiffness
coupling to the actuator, friction, wrong preloading,wrong force coupling, misalignment of coupling
faces from actuator to mechanics reducesignificantly usable stroke, accuracy, force
generation and make the use of piezo actuator
more or less worthless. Poor designing impact
further actuator’s long-term reliability.
Fig. 16 shows the consequences of inhomogeneous
high force loading: A stack with excessive edge
squeezing / pressure of the ceramic-stack by an
improper force coupling (Fig. 17 b, c). Cracks are
generated within the active ceramic section
resulting in electrical break down and arcing.

Coupling of actuator and mechanics
Optimum actuation performance is achieved byfollowing a few simple rules● The coupling face of the mechanics shall covercompletely actuator’s end faces to achieve
maximum force transfer (Fig. 17 a). The contact
force shall be homogeneously distributed overthe contact area.
● When a high load pressure is applied, thecoupling faces of actuator and mechanics faces
shall be absolutely plain (eg. by grinding) to avoid
local overload of the ceramic front face.
● The resulting load force vector shall coincide withactuator’s axis. Within a virtual cylinder of+/- 10% of actuator’s cross-section (Fig. 17 a) to
avoid excessive bending and shear stress. Forcemisalignment tolerance 움 becomes more criticalfor increased ratios actuator length / diameter.
For high dynamic operation, actuator’s axis shallfurther hit the centre of mass of the attachedmechanics to avoid dynamic torque.

mechanics

piezo-stack

Fig. 16: Failed actuator stack, caused by a wrong coupling to
the actuated mechanics. Local edge pressure exceeded
ceramic’s stability with subsequent electrical break down
after approx. 800 hours.
14움Fig. 17 a: Perfect plain-plain coupling of piezo-stack and attached mechanics by floating axis orientation of the mechanics.
Acceptable tolerance 움: See above2.3 Mounting advises● When the mechanical partner can read just itself

by a free suspension (floating axis) according
actuator’s plane face, no problems will occur.
● Coupling of piezo actuators to guided

mechanisms (axis orientation not floating).
One of most widespread design mistake iscoupling a plain-faced actuator directly to a plainfaced guided mechanism (Fig. 17 b) Even theslightest misalignment between the orientationsof the both plains leads immediately to edge
squeezing with very high local spot pressuresand subsequent ceramic damaging (Fig. 16),
especially under high force load conditions.

moving partIn a similar way, the plain-plain coupling of anaxially acting stack with a rotating lever
arrangement will lead to a fundamental edge
squeezing situation in any case (Fig. 17 c).
Do not try this!
In the above cases, it is a must to decouple theaxis orientations by using spherical / plain
coupling or flex hinges or other means!
● The above requirements are valid at any timeand any state of the system during set up andoperation.

moving part

moving partwrong
critical edge
squeezingcorrect

correct

piezo-stack

piezo-stack

piezo-stack

웁

웁

웁

Fig. 17 b: Incorrect /correct coupling of linear guided mechanics

pivot

wrong
critical edge
squeezing

pivot

correct

Fig. 17 c: Incorrect /correct coupling of a rotating mechanism
15

2.3 Mounting advises

Bonded contacts piezo-stack / mechanics
The contact between actuator stack and mechanics/ actuated components is often done via gluing.
The basic considerations about the contact quality
with respect to alignment remain valid:
Misalignment of the joined parts as shown in
Fig. 17 b, c results in strong bending forces andtensile stress within the piezo ceramics reducing
both performance and reliability.

inactive PZT-layer

activated PZT-layerd33

The only compromise for gluing can be made withrespect to the flatness of the mechanical part,
because the adhesive has to some extent a “filler”
property.
For applications within a range of -20 °C / +60 °C,
any good quality epoxy can be used. The curetemperature shall be held rather low to avoid
thermally induced stress, when the CTEs of thejoined parts is remarkably different. The thickness ofthe glue lines shall be held rather thin (< 50 µm) to
avoid a “softening” of the coupling quality.
For “exotic” driving conditions like very low or very
high temperature, vacuum application etc. special
adhesive formulations and gluing techniques arerecommended.
Ask PIEZOMECHANIK for support.

d31

Fig. 18 a: Action of a free PZT-layer

inactive PZT-layer
activated PZT-layer

Piezo-chips
On the other hand too hard and too thin glue-lines
increase the “d31-clamping” effect, what can hinderor block the axial motion especially of piezo-chips(Fig. 18 a, b, c).
For coherent optical applications, unwanted tiltingof mounted optical element will then occur. Further,thin optical elements can be distorted by a hardcoupling to a piezo-chip (bending structure).

hard glueline

Fig. 18 b: Hindered expansion of a PZT-layer by clamping bya hard glue line together with a rigid substrateactivated PZT-layer

Only when the d31-planar contraction is nothindered, a thin piezo-chip will show the maximum
axial d33-expansion and planar displacement.
Ask PIEZOMECHANIK for more details. A special
brochure will be provided on request.

substrate

Fig. 18 c: Bending structure by gluing a PZT-layer onto a thin
substrate.

16

2.4 Influences from ambient

Piezo stacks are electrically highly active elements with high electrical fields atstack’s surface.

For mounting stacks into metal constructions,ensure sufficiently large insulation gaps between
stack’s side-faces and the surrounding
mechanics. A PZT-stack-structure is rather
sensitive to any contamination by conductive
species like electrolytes. Leakage currents will
set on, leading to electro corrosion andsubsequent short circuiting of the actuator.
Contact to aqueous liquids shall be avoided.
On the other hand stacks with polymer coating
can be operated within non-aqueous fluids (e.g.
Diesel fuel, transformer oil, silicon oil), what canbe used for high efficient cooling of dynamicallyoperated stacks.
Do not touch bare stacks with bare fingers.
Cleaning of coated and uncoated stacks shall bedone only with 100% iso-propanole.
Never use acetone!

PIEZOMECHANIK’s PSt 150 osi-actuators areworld-wide in use since decades, runningsuccessfully with highest reliability under widest
variety of applications for very different driving
conditions with direct access to ambient
atmosphere.
Experience shows, that only for a very high humidity
loading of the ambient atmosphere (“tropical”

conditions) in context with long-term applied
maximum voltage additional measures are required
to ensure high reliability.
These effects can be overcome by incorporating thestacks into hermetically sealed casings or by
applying tightly a pinhole-free metal-foil toactuator’s surface as humidity protection.
Metal foil encapsulated osi-samples (Fig. 19) arerunning since 2 years at 150 V DC / 85% rel.
humidity at 20 °C without any degradation.

Fig. 19: Metal foil encapsulation of a PZT-stack17

2.5 Electrical operating conditions

Voltage ranges, polarity:
Piezo-actuators are poled components.
Usually, the positive pole is indicated e.g. by
A red pigtail wires
B printings, dots
C long wire

The piezo mechanical data like stroke andblocking force / max. force generation depend on
the applied voltage levels.
The maximum ratings of stroke and force aredefined for uni-polar or semi-bipolar operation as
follows●●

Unipolar mode e.g. 0 V/ (+)150 V
Semi-bipolar operation e.g. (-)30 V/ (+) 150 V
for stacks and chips PSt 150.

Due to the larger voltage swing, the semi-bipolar
operation offers potentially larger strokes and force
generation (blocking force) than the uni-polar mode.
PIEZOMECHANIK offers the semi-bipolar amplifiers
SVR to get maximum stroke and force generation(blocking force) from a stack-actuator.
Fig. 20: Actuator’s polingIn the following(+) indicates a polarity of the applied voltage parallelto actuator’s poling, whereas(-) means a counter polarity, opposite to actuator’spoling.

18

The stated actuator voltage ranges shall not be
exceeded.
A short term overpowering of the upper (+) voltage
limit of a multilayer-structure by 10% does not
immediately result in a break down, but thereliability is strongly reduced by time. Still higher
voltages go the risk of immediate arcing andelectrical break down.

0
2.5 Electrical operating conditions

Using too high counter-voltages (below the (-) limitof the semi-bipolar range) implies the risk of depoling the PZT-ceramics. Attention must be paid
here to operation at elevated temperatures, what
lowers potentially the de-poling stability.
The 150 V-osi-Actuators PSt 150 are easy to handle
with regard to de-poling: By applying for a few
seconds a voltage of about 100 Volts, the ceramic
will be reactivated completely without any losses in
performance.
The isi-actuators and Piezo-Chips are more critical:
On one side they show higher temperature stability
by a higher Curie-temperature of the PZT-ceramic,
but in case of de-poling or polarity-reversal, theactuator properties can change irreversibly.
The risk of oversized amplifiers is the highacceleration force, what will be created, when atransient interference signal is picked up. When theactuator system is not adapted to such highaccelerations, the actuator will be damaged.
Oversized amplifiers are costly and may show
additional disadvantages like elevated noise levels.

1. Rule of thumb: Use only power supplies with
voltage ranges matched to the actuator ratings.
Power consumption, current levels:
Piezo-stacks behave like capacitors in the subresonant frequency range.
Therefore, a current flows only during a voltage
variation for altering the position and / or force
status of an actuator. The faster the variation is
the higher are the required currents.
2. Rule of thumb: Define precisely the electricalcurrent or power level to get the required
dynamics of your actuating system (rise-/ falltimes, see brochure “electronics”).
Do not oversize significantly the max. current
and power ratings of the used amplifier.

Contact PIEZOMECHANIK for selecting wellmatched electronic driving systems.

19

3

Products,
technical data

Piezo-stacks / rings PSt / HPSt 150 with superior osi-technology:– For highest efficiency, reliability and ease of handling.
– Covering nearly all actuator applications ranging from static to highest dynamic
operation profiles.
– High mechanical stability and tight tolerances of dimensions and piezo-mechanicaldata highlight these actuator as OEM-components for industrial use.
Piezo-stacks PSt-HD 200 in special isi-configuration– For highly dynamic applications at elevated temperature levels
Piezo-chips PSt 150 with active thicknesses up to 3 mm with isi-technology and buried-electrodedesignHigh axial resonance frequencies suitable for sensor/ generator applications– Very low voltage 50 V type with– Very high charge generation available (energy harvesting)General remarks on technical data:
Voltage ranges (see chapter 2.5)(+) Umax maximum operating voltage according
actuator’s polarity(-) U
voltage polarity opposite to actuator polarity
Strokes
Maximum ratings defined for semi-bipolar and unipolar driving voltage e.g. forPSt 150: 0 V/ (+)150 V and (-)30 V/ (+)150 V
Capacitances– Measured at low field excitation at room
temperature– Manufacturing tolerances up to +/- 20%– Capacitance can depend on high field excitationand temperature
Resonant frequencies– Refer to axial mode
– Defined for one side fixed piezo-element(other modes like planar diameter not taken into
account)

20

Stiffness
Inverse compliance,– measured at short circuited elements or undervoltage control operation– measured with a static preload of at least of
10% of actuator’s maximum load
Blocking force
Means maximum force generation of an actuator
Depends on the applied voltage variation
Stated values refer to maximum semi-bipolar
operation.
Maximum uni-polar operation gives about 30%
lower values
Maximum compressive load
Maximum constant load range, where actuator’s
properties are not reduced.
Overload with risk of mechanical damage occurs
only for much higher force levels or for very large
ratios length / diameter (bending).
Attention has to be paid to avoid local overload of
actuator’s end faces (see chapter 2.3).

3.1 Piezo-stacks PSt 150 / HPSt 150 (osi-type)Fig. 21: Piezo-stacks PSt 150 and piezo-rings HPSt 150 in unsurpassed osi-technology

Top features:● 100 % active PZT-ceramic (no inactive “deadzones” cross-section for maximum stroke andforce generation●

Highly reliable and robust operation due toabsence of intrinsic stress●High quality polymer coating gives a robust finish
and ruggedizes especially small cross-section
elements.

●

Adoption to exotic driving conditions●

Tight manufacturing tolerances●

Low tilt operation●

Large cross-sections up to 25 x 25 mm

Suitable for a widest range of applications. Heatmanagement allows very high dynamic operation●

High bending stability due to absence of interrupts / slots / cracks in the ceramic surface

Ask PIEZOMECHANIK in case of special driving
conditions●

Large temperature range -273 °C up => +120 °C

213.1 Piezo-stacks PSt 150 / HPSt 150 (osi-type)

type
osi-stack(+) Umax 150 V

ceramiccrosssectiona x b /mm2

length L 1)

Max. Stroke 2) capacitancestiffnessnF

Resonance
frequency
kHz

mm

µm

PSt 150/2x3/5

2x3

5

6.5/5

PSt 150/2x3/7

2x3

9

PSt 150/2x3/20

2x3

PSt 150/3.5x3.5/7

3.5 x 3.5

PSt 150/3.5x3.5/20

3.5 x 3.5

Blockingforce 3)

N/µm

N

Max. load
force
N

70

150

45

300

300

13/9

170

100

25

300

300

18

28/20

340

50

12

300

300

9

13/9

350

100

50

800

800

18

28/20

800

50

25

800

800

PSt 150/5x5/7

5x5

9

13/9

800

100

120

1600

2000

PSt 150/5x5/20

5x5

18

28/20

1800

50

60

1600

2000

PSt 150/7x7/7

7x7

9

13/9

1800

100

240

3500

4000

PSt 150/7x7/20

7x7

18

28/20

3600

50

120

3500

4000

PSt 150/10x10/7

10 x 10

9

13/9

3600

100

500

7000

8000

PSt 150/10x10/20

10 x 10

18

28/20

7200

50

250

7000

8000

PSt 150/14x14/20

14 x 14

18

28/20

14500

47

500

15000

16000

Ring-actuators(+) Umax 150 V

Diameters
axb

HPSt 150/14-10/12

14 x 10

13.5

16/12

2600

75

250

4500

7000

HPSt 150/20-15/12

20 x 15

13.5

16/12

5000

75

450

8000

12000

1)

direction of expansion
activation (-)30 V
3)blocking force = max. force generation
defined for max. semi-bipolar operation
2)

a

b

Dimensions
a, b, L refer to the ceramic structure,
Tolerances: +/- 0.03 mm

ØaØbMaximum voltage range(-)30 V/ (+)150 V
L

L

앒3

Fig. 22: Actuator PSt with standard coating22

앒3

3.1 Piezo-stacks PSt 150 / HPSt 150 (osi-type)

Options
Position sensing by strain gages
Spherical end-pieces(up to cross-sections 10 x 10 mm) (Fig. 23)
Low temperature operation
Cryo option 1: special coating
Cryo option 2: electrical contact by kaptoninsulated Manganin wires forminimizing heat loadabTemperature range-273 °C thru approx. +120 °C (depends on coating,see below)(beyond 100 °C, PZT-performance degrades
reversibly)
Coatings
standard: high quality epoxy-based encapsulation
temperature range -50 °C thru +120 °C
vacuum / UHV grade thickness up to 0.5 mm
Special coatings optional eg. for cryo applications
thin coatings for stack packaging(thickness < 50 µm)
Extended to such actuators PSt. 150 / axa /40 on
request.

r= a
2

L

앒3

Fig. 23: Actor with spherical end-pieces233.2 Piezostacks PSt 150 hTc with reduced
capacitance (osi-type)
A new PZT-material is available in combination withthe osi-stack technology.
The stacks are featuring reduced electrical capacitance and self-heating, when operated dynamically.
These stacks are preferentially used for vibration
excitation and dynamic positioning applications,where mainly high strain rates are required together
with reduced force generation.
Typical applications are vibration generationequipments or scanners for optics, where power
consumption and self-heating are a concern.

PSt 150 hTc-stacks take up only 2/3 of thecharging current to get the same dynamic
motion profile compared to the standard PSt
150 stacks (see page 22).
Power dissipation is reduced equivalently
resulting in a remarkably lower self-heating.
Due to the higher Curie-temperature of thisPZT-material, the stacks can be operated at
higher temperatures without significant change
in performance.

Comparison of important parameters between PSt 150 standard and the new PSt 150 hTc piezo ceramics(Voltage range (-)30 V / (+)150 V)
PSt 150

PSt 150hTc

100%

65% !

of a stack 10x10xL=18 mm/stroke 18 µm at 80 Hz/ambient air cooling

60°

45° !

Curie temperatur

150 °C

200 °CElectrical capacitance at room temperature

100%

60%

Example: stack 5x5xL = 18 mm

1,8 µF

1,05 µF

Electrical capacitance at 70 °C

135%

80%

100%

90%

100%

75%

Charging current I
Sine 80 Hz/equal stroke, no force generation required

Self-heating

Strokefor equal voltage variation

Blocking force
for equal voltage variation

Operating temperature range of piezostacks
PSt 150 hTc:
Standard coating (green):-50 °C thru +125 °C (long-term), 140 °C short-term(Check page 22)
Cryo coating:-273 °C thru +125 °C / 140 °C

24

3.2 Piezostacks PSt 150 hTc with reduced capacitance(osi-type)

Product range: osi-stacks PSt 150 hTc
aPSt 150 hTc / 5x5/7
PSt 150hTc / 3.5x3.5 /18
PSt 150hTc /5x5 /18
PSt 150hTc / 7x7/18
PSt 150hTc /10x10/18
PSt 150 hTc/14x14 /18








PSt 150 / 5x5 /7
PSt 150 / 3.5x3.5 / 20
PSt 150 / 5x5 / 20
PSt 150 / 7x7/ 20
PSt 150 /10x10 / 20
PSt 150 / 14x14 / 20b

L

Voltage range -30 V / +150 V
 100% compatibility of PSt 150 standard and PSt
150 hTc stacks regarding outer dimensions, voltage
range, coatings, options !
Longer stacks: on request

3

Fig. 24: piezo stack PSt 150 hTc (dimensions see page 22)

Piezoactuator PSt 150 hTc /... /… VS... withpreloaded casing(check main catalogue for standard)
Available types:
PSt 150 hTc / 5 /... VS 10
PSt 150hTc / 7/... VS 12
PSt 150hTc / 10 /... VS 15
PSt 150hTc / 14 /... VS 20
PSt 150 hTc / 20 /... VS 25
Voltage range -30 V / +150 V
 100% compatibility of PSt 150 standard andPSt 150 hTc stacks regarding outer dimensions,voltage range, options !

Fig. 25: piezo actuator with casing and internal preload, using
PSt 150 hTc (check also main catalogue)

253.3 Piezo-chips PCh 150 / HPCh 150 (isi-type)●

Flat multilayer elements● for ultra-compact actuator arrangements● for high axial resonant frequencies● suitable for d31 and d33 action●

for force sensing / generator application
special 50 V-type with very high charge
generation rate

Fig. 26: Piezo-chips
Actor typeisi-Stacks(+) Umax 50 V
PCh 50/5x5/2(+) Umax 150 V
PCh 150/3x3/2
PCh 150/5x5/2
PCh 150/7x7/2

Ceramic
crosssectiona x b/mm2

thickness L 1) Max. Stroke2) capacitance

mm

µm

nF

Resonancefrequency
kHz

stiffness

Blockingforce3)

N/µm

N

Max. load
force
N

5x5

2

>3/>2

1250

> 500 kHz

500

1500

2000

3x3

2

>3/>2

30

>500 kHz

190

500

500

5x5

2

>3/>2

110

>500 kHz

500

1500

2000

7x7

2

>3/>2

240

>500 kHz

1000

3000

5000

2

>3/>2

480

>500 kHz

1900

6000

10000

PCh 150/10x10/2

10x10

Ring-actuators(+) Umax 150 V

Diameters
axb

HPCh 150/6-2/2

6x2

2

>3/>2

110

>500 kHz

400

1500

2000

HPCh 150/8-3/2

8x3

2

>3/>2

200

>500 kHz

900

2500

4000

HPCh 150/12-6/2

12x6

2

>3/>2

500

>500 kHz

1400

5000

5000

HPCh 150/15-8/3

15x8

3

>4/>3

790

>300 kHz

1800

7000

10000

1)

direction of expansion
semi-bipolar/unipolar activation
3)
blocking force = max. force generation defined for max. semi-bipolar operation
2)26

3.3 Piezo-chips PCh 150 / HPCh 150 (isi-type)

Dimensions
a, b, L
tolerances:a, b +/- 0.3 mm
L +/- 0.1 mmaaMounting advises: Piezo-chips show verysmall stroke rates due to their short active
length L.
Incorrect mounting will impact force and stroke
generation, leading to insufficient performanceand unwanted bending and tilting. Please follow
instructions in chapter 2.3.

b
b

L

L

Fig. 27: Piezo-chips PCh, PHCh

Maximum voltage ranges
PCh 50: (-)10 V/ (+)50 V
PCh 150: (-)30 V/ (+)150 V
Temperature range-273 °C thru approx. +130 °C
Surface insulation
buried electrode, no coating27

3.4 Special designed stacks and rings

Fig. 28: Special designed stacks and rings– With regard to length, cross-section(squaric, rectangular, cylinders)– Voltage ranges– Finish (optional end-pieces, mechanicalcouplers)

Piezomechanik · Dr. Lutz Pickelmann GmbH
Berg-am-Laim-Str. 64 · D-81673 Munich · Phone ++ 49 / 89 / 46 14 67 96 · Fax ++ 49 / 89 /4 31 64 12
e-mail: info@piezomechanik.com · http://www.piezomechanik.com

Stand: Mai 2011

On request, PIEZOMECHANIK delivers special
designed stack and rings: