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The Piezoelectric effect was discovered
by Jacques and Pierre Curie
Piezo crystals become electrically charged
when deformed under mechanical stress
In 1880 Jacques and Pierre Curie discovered that when deformed under mechanical stress, quartz crystals became electrically charged – positively and negatively – on prism-shaped surfaces. They called this reaction the piezoelectric effect. Above a certain temperature (called the Curie temperature) these kinds of materials possess a cubic elementary cell with a centre of symmetry. The main areas of the positive and negative charges are found in the centre of the elementary cell of the crystal. The materials are paraelectric. There is no detectable piezoelectric effect.
In the manufacturing process, after sintering, a shift of the ions of the elementary cell occurs when cooling below the Curie temperature. The positive and negative charges are no longer in the center. The symmetry center is lost and a spontaneous polarization of the elementary cell occurs. The elementary cell now has an electric dipole.
The dipoles influence each other and spontaneously form areas with a uniform orientation, so-called “weissch domains”. The polarization directions of a piezoceramic are statistically equally distributed, so that the macroscopic body has no polarization and is therefore not piezoelectric.
If the ceramics are exposed to a strong electric field, these domains remanently align themselves to this field. Only with the help of this polarization process the piezoceramics acquire their piezoelectric properties, which are important for industry.
Deformed under mechanical stress, Piezo crystals become electrically charged.
The same materials undergo dimensional change under the influence of an electric field.
The piezoelectric effect is the ability of certain crystalline materials to convert mechanical stress into electrical signals and vice versa. Every Piezo Sensor can also be used as a Piezo Actuator. The industrially most important piezoelectric materials consist of ferroelectric polycrystalline ceramics. These piezoelectric materials possess a Perowskit crystalline structure.
Working principle of bending actuators and sensors
Piezo bending actuator
When two piezoelectric ceramic plates are bonded together with a supporting material and counter-actuated, this results in a pronounced deformation of the composite similar to the case of a bimetal. Its design enables deflections of several millimetres or forces up to several Newton and a short cycle time of a few milliseconds can be achieved.
Therefore, the Piezo bending actuator can be employed as a high performance and fast-reacting control element. Due to the high speed of deflection, productivity is higher compared to the use of electromagnets. As a result of its compact design, the Piezo bending actuator takes up significantly less space.
Piezo bending sensor
Piezo ceramic benders can also be used as sensors. Bending generates a charge/ a voltage on both ceramic layers. Parallel connecting both ceramics layers will add their charge.
Thus they are suitable for measuring big and small movements, vibrations, accelerations and for energy harvesting. Our Piezo benders usually have a working life of more than a billion cycles.
The contraction of the ceramic when the operating voltage is applied results in deflection and force on the tip of the bending actuator. Or, if a force is applied to the tip, this generates an electrical charge.
Important parameters for bending actuators
typically up to 2 mm
max. up to 10 mm
typically up to 0.7 N
max. up to 5 N
Driving voltage (DC)
to 230 V
Typical characteristic values of piezoceramic bending actuators are dominated by their total displacement and the blocking force at the operating voltage.
The maximum deflection of a Piezo bending actuator and the maximum blocking force can be easily determined.
Performance features of three different kinds of Piezo actuators: Comparison of values of force and deflection of stacks, actuators with path transformations and bending actuators.
Generating ultrasound with Piezoceramics
Piezoelectric ceramic resonators can be set into high-frequency oscillations (ultrasound) by means of defined voltages and are therefore perfect ultrasonic generators. The ultrasonic speed of piezos is often used for cutting procedures, the removal of tartar at the dentist or for imaging diagnostics: Ultrasound screening.
Piezoceramics are therefore predestined for the atomization of liquids or other media not only because of their high reliability. A systematic distinction is made between three proven methods for generating atomization based on piezoceramic elements.
An aerosol (atomized medium) can be generated by cavitation, for example. Focused ultrasonic waves cause small bubbles to explode, thus emitting the aerosol on the surface of the liquid. The stimulation of a surrounding surface (by a piezoceramic) is another option for the reliable atomization of media.
By far the best method is a so-called mesh atomizer. Here very homogeneous aerosols are achieved at low emission speed. A perforated perforated disk (surrounded by piezoceramics) vibrates ultrasonically on the liquid surface and thousands of laser-cut holes emit uniform droplets at low speed.