Piezocomposite0 pages

THEORY - HIGH POWER ACTUATORS

Piezocomposite Actuators
Cofired Multilayer Actuators
For the past few decades “cofired” multilayer stacks has
been the state of the art method used for constructing piezo
actuators. However there are a variety of applications where
multilayer stacks reach their natural limitations.
Multilayer stacks consist of many ceramic layers (each approx. 100 µm in thickness) with thin (1 µm) electrodes between them. After stacking these layers the compound is
then sintered at high temperatures (cofiring).

Figure 1: Piezocomposite stack actuator
made from single
piezoceramic discs and
intermediate metal
electrodes

Multilayer actuators are operated with low voltages up to
200 V.

Design of Piezocomposite Actuators

Piezocomposite Ring Actuators are preferred for

Piezocomposite actuators are made from completely sintered single PZT discs (thickness 0.3 to 0.5 mm) and separate
intermediate metal foil electrodes which are held together
by special high quality adhesives. Therefore these discretely
stacked actuators are a composite material with some outstanding properties.

•t ptical applications
O
•t pplications with high frequencies requiring effective
A
cooling and special thermal behavior
•t pplications with high bending stability
A

Stiffness

Piezocomposite actuators should be used to generate:
According to
•t igh forces up to 50 kN
H
•t igh accelerations up to 100’000 m/s2
H
•t hort pulses
S
•t o withstand loads up to 70 kN
T

, the stiffness of Piezocom-

posite Actuators increases with the cross section and decreases with the length of the actuator. Piezocomposite Actuators with a preload show an elastic modulus nearly as
high as that of multilayer stacks.

Piezocomposite Actuators

Low Voltage Multilayer Stacks

preferred use

large cross sections generating high forces

small, medium cross sections for
low volume elements

applications

high dynamic applications,
shock generations,
shakers, vibration generation
short impulse excitation

positioning,
scanning,
integration into more dimensional
positioning systems

operating voltage

500 V - 1000 V

max. electrical field strength

up to 200 V
approx. 2 kV/mm

max. strain

0.1 to 0.15 % related to the stack length

force generation

same order related to the same cross section

positioning accuracy

same for both types: depending on the electrical supply and environmental conditions

electrical capacitance / volume

approx. 10 nF/cm3

approx. 2,5 µF/cm3

production technology

stacking of sintered ceramic plates

stacking of non sintered ceramic
layers and cofiring

material variety

large

small

operating temperature range

up to 200 °C

up to 100 °C

electrical current for dynamic
applications / per volume

low current

high current

cross section of ceramics

diameters up to 35 mm

up to 14 x 14 mm2

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