Last Updated on April 10, 2023 by You Ling
multi-layer piezoelectric ceramics
Piezoelectric stack actuators are the most common type of piezoelectric actuators. They have a wide range of applications. However, many people still do not have a good understanding of how to use and operate piezoelectric stack actuators. Read this article to learn more about how to use piezoelectric stack actuators.
1、What are piezoelectric stack actuators (multi-layer piezoelectric ceramics)?
Piezoelectric actuators are piezoelectric actuators made of piezoelectric materials with actuation functions. It utilizes the inverse piezoelectric effect of the piezoelectric element, and can generate different displacement amounts under different voltage driving.
Piezoelectric stack actuators are formed by bonding piezoelectric ceramic substrates through a co-firing process (the thickness of a single-layer piezoelectric ceramic substrate is about 100μm). Piezoelectric ceramics prepared by this process can withstand high pressure, have high rigidity, but have limited tensile strength.
Piezoelectric stack actuators consist of many ceramic sheets. Its structural feature is that the power supply electrode is designed on both sides of the ceramic sheet, and the entire cross-sectional area of the ceramic can participate in actuation, which has a large output, excellent performance, and no local electric field deformation, making it less susceptible to point stress.
2、Classification of piezoelectric stack actuators
According to the different driving voltages, piezoelectric stack actuators can be divided into two types: low voltage and high voltage. The production processes for these two types of ceramics are completely different:
The voltage range of the low voltage piezoelectric ceramics is 0-150V. The ceramic layer and the internal metal electrode layer are stacked together before high-temperature sintering. The internal electrode is a very thin metal film (with a thickness of about 1μm). This ceramic production process is usually called the “single-piece co-firing process.”
The voltage range of the high voltage piezoelectric ceramics is 0-500V or 1000V. The PZT plate/piece has been completely sintered and made before stacking. The inserted electrode is made of separate thin metal foils. The entire structure is fixed together with a special high-quality adhesive. Therefore, the high voltage stacked ceramic is not a single piece of ceramic, but a composite material.
3、Applications of piezoelectric stack actuators
Piezoelectric stack actuators have a very wide range of applications and can cover almost every field, such as semiconductor technology, aerospace, image processing, low temperature and vacuum environments, biotechnology and life technology, astronomy, adaptive optics, microscopy and imaging, measurement/laser technology/optical detection/tribology, data storage technology, precision processing (metal, optical, laser cutting, diamond polishing), nanotechnology, nano-manufacturing and nano-automation, optoelectronics, communication and integrated optics, new drug design and medical technology, etc.
The industrial applications of piezoelectric stack actuators include industrial processing tools that require precise movement. Nano-positioning is used in laser adjustment, laboratory equipment (pipettes and pumps), and semiconductor machinery. Another common industrial application is active vibration control for wind turbines, motors, and other vibration-sensitive equipment. Piezoelectric stack actuators control vibration by generating reverse motion, thereby suppressing bad vibrations in mechanical structures. Inkjet printers also rely on the piezoelectric stack effect to initiate printing. When a voltage is applied, the piezoelectric stack actuator produces enough energy to print.
4、Precautions for using piezoelectric stack actuators
Since the stack-type piezoelectric ceramic is formed by stacking and bonding and co-firing piezoelectric ceramic sheets, the compressive strength of the ceramic is much greater than its tensile strength.
When the ceramic is dynamically applied, both compression and tension forces are produced due to the acceleration of the ceramic material itself. To avoid damaging the piezoelectric ceramic, a preload can be applied to protect the ceramic. In general, the preload size is one-tenth of the maximum load.
The actuator can only withstand axial forces and cannot withstand lateral and shear forces.
Please apply the force to the entire surface to ensure uniform distribution of force and avoid point loading.
To avoid short circuits, do not directly attach metal sheets to the top and bottom surfaces. Instead, attach film to the metal surface or add an insulating gasket between the ceramic surface and the metal sheet.
The stack-type piezoelectric ceramic is very sensitive to tensile stress. To improve reliability, it is recommended to use a pre-tightening force.
Epoxy resin glue is very suitable for bonding piezoelectric ceramics to other surfaces. To avoid damage to the ceramic’s performance, the installation process should avoid mechanical clamping and glue sticking to the side.
Piezoelectric ceramics cannot withstand shear, lateral or torsional forces. The force applied to the moving end of the ceramic should be as close to the center of the ceramic’s movement direction as possible, and the edges of the piezoelectric ceramic should be kept free from clamping forces.
Piezoelectric ceramics cannot withstand point loading. During installation and use, avoid squeezing the edges and causing damage to the ceramic.
4.81、Do not use outside the voltage range given in the parameter table.
4.82、Do not scrape off the side coating of the stack ceramic.
4.83、Stack ceramics without pre-tension cannot withstand tensile forces. It is recommended to load a pre-tension force equal to one-tenth of the output.
4.84、The environment where the stack ceramics are located should be kept dry.
4.85、Temperature changes or load changes can cause charging inside the ceramic. Before using the ceramic, it is recommended to discharge the ceramic with a few hundred ohms resistor.
4.86、Prevent the surface of the stack ceramics from coming into contact with conductive or corrosive substances. Use isopropyl alcohol to clean the surface, and avoid contact with isopropyl alcohol at high temperatures and excessive ultrasonic cleaning.
4.87、The red lead is connected to the positive pole of the power supply. The side of the piezoelectric ceramic without leads and with the dot electrode facing is the positive pole.
4.88、Avoid pulling or tugging the wires, and do not move the ceramic by pulling it. Instead, move it in a gentle manner.
4.89、Do not directly touch the ceramic resin with your hands, as it may reduce the stability of the ceramic.
4.9、If you use glue to fix the ceramic, make sure that the glue between the ceramic and the bonding surface is very thin, and gently press it to fix it.
5、Case Pictures of piezoelectric stack actuators from He-Shuai Company