With the continuous development of high-tech, people's requirements for the precision of modern technology are also increasing. Piezoelectric materials are made into sensors, actuators, etc. for precision/ultra precision applications, enabling measurement of small deformations, stress measurement, nano positioning, and non-destructive testing of objects.
The advantages, disadvantages, and application scenarios of each piezoelectric material are different. Piezoelectric ceramics have strong piezoelectricity and high electromechanical coupling coefficient. There is no requirement for their shape during processing, and they can be made into any shape. They have a great price advantage and can be produced in large quantities. They can also be deeply processed and combined with other functional devices to meet the requirements of different fields. Therefore, they are widely used in various modern scientific technologies and daily life that require ultra precision machining.
Application of piezoelectric ceramics in precision/ultra precision fields
Due to the positive and negative piezoelectric effects of piezoelectric ceramic materials, they have been widely used in devices such as piezoelectric sensors, drivers, transducers, and filters. The application scope covers many fields such as aerospace, military, information electronics, industrial machinery, medical, automotive, etc. According to statistics, it is expected that the global market size of piezoelectric materials and devices will reach 35.4 billion US dollars by 2026. Among them, the production, use, and export of piezoelectric materials and devices in China account for over 60% of the global scale.
01 Piezoelectric transducer
Piezoelectric transducers utilize the piezoelectric and inverse piezoelectric effects of piezoelectric ceramics to achieve the mutual conversion of electrical and acoustic energy. Piezoelectric ultrasonic transducer is an underwater acoustic device that emits and receives ultrasonic waves. A piezoelectric transducer in water induces charges at both ends of the transducer under the action of sound waves, which is called a sound wave receiver; If an alternating electric field is applied to a piezoelectric ceramic sheet, the ceramic sheet will become thinner and thicker at times, while generating vibration and emitting sound waves, which is the ultrasonic transmitter.
Piezoelectric transducers are widely used in underwater navigation, ocean exploration, ultrasonic cleaning, solid-state testing, as well as medical imaging, ultrasonic diagnosis, and ultrasonic disease treatment. Another application area of piezoelectric ultrasonic transducers today is telemetry and remote control systems.
● Applied in the field of non-destructive testing. Non destructive testing technology refers to the use of sound, light, electricity, magnetism, and other techniques to detect the presence of defects or unevenness in the inspected object without damaging it, and to provide information on the size, location, nature, and quantity of defects.
The commonly used non-destructive testing methods such as ultrasonic testing, radiographic testing, machine vision testing, eddy current testing, and vibration testing are still in their early stages for concrete damage detection and wood structure damage detection. They cannot locate and describe internal damage, and the sensor prices are expensive. Piezoelectric ceramics have the characteristics of flexible use and low price, which can achieve the localization and intelligent detection of concrete damage and wooden structure damage.
● Applied in the field of piezoelectric energy harvesting. Piezoelectric energy harvester utilizes the resonance characteristics of piezoelectric oscillators and the piezoelectric effect principle of piezoelectric materials to convert solar energy, vibration energy, noise energy, and other environmental factors into electrical energy. This principle is also applied in piezoelectric ceramic ultrasonic motors. At present, piezoelectric energy harvesting technology is mainly applied in road piezoelectric power generation, converting the mechanical energy generated by vehicle driving into electrical energy.
The most commonly used piezoelectric material selection is lead zirconate titanate (PZT). However, research has shown that under high-frequency cyclic loading, PZT is prone to fatigue cracking and brittle fracture. Therefore, PZT cannot withstand excessive stress in piezoelectric energy harvesting systems, and piezoelectric polymer polyvinylidene fluoride (PVDF) can be used. Research has shown that PVDF has the advantages of high toughness, long life, and high efficiency.
02 Piezoelectric sensor
When a piezoelectric sensor works, pressure is generated on the piezoelectric element, which in turn generates an electric charge. After passing through the amplifier and conversion impedance components inside the sensor, the electric charge will form an amount of electricity proportional to the external pressure, and then release the generated electricity to ensure the normal operation of the sensor. It has been widely used in acoustics, medicine, mechanics, and navigation.
● Applied in the fields of micro displacement and 3D surface measurement. Piezoelectric ceramics are mainly used in ultra precision feed systems in the field of micro displacement. The micro displacement measurement tool uses an inductive micrometer with an accuracy of 0.01 μ m, a range of 0-10 μ m, a worktable stiffness of 200N/μ m, and a displacement stroke of 27.6 μ m. During the loading voltage and discharge process of piezoelectric ceramics, dynamic displacement occurs. The displacement of piezoelectric ceramics drives the worktable to produce feed motion, and the displacement sensor generates displacement feedback to the control system to form a closed-loop control. Communicate data between the inductance micrometer and the computer, and use Matlab or LabVIEW to achieve motion control of the measurement platform.
Principle block diagram of feed system
The main methods used in the field of 3D surface measurement include mechanical probe method, optical probe method, scanning probe method, and phase-shift interferometry method, among which phase-shift interferometry method has the best effect.
● Applied in the field of small deformation and stress measurement. In the field of small deformation and stress measurement, piezoelectric sensor elements are mainly used to apply the characteristics of piezoelectric ceramics to force measurement, as well as the measurement of non electric physical quantities that are ultimately transformed into force.
In terms of small deformations, traditional measurement methods such as vernier calipers and optical levers cannot meet the needs of precision and ultra precision fields. Therefore, using smart materials such as piezoelectric ceramics and sensors to measure small deformations in precision and ultra precision materials is currently an important research direction.
03 Piezoelectric driver
Piezoelectric actuators utilize the inverse piezoelectric effect of piezoelectric materials to achieve motion control. The resolution of piezoelectric ceramics can reach the nanometer level or even one order of magnitude higher, and can move in a straight line along a specified direction. When an electric field is applied, piezoelectric materials undergo mechanical strain, resulting in motion. This type of motion can be used to drive mechanical systems, achieving precise position control and motion control. Piezoelectric actuators are widely used in high-precision and fast positioning applications, with many advantages such as high output force, small size, fast response, and high stiffness.
Piezoelectric ceramic actuator
The driver is the core device of the micro positioning platform, which can be used to drive the micro positioning platform. Micro locators are mainly used for positioning control with micrometer and sub micrometer precision, such as in the production of optical instruments, fiber optic docking, high-precision 3D micro motion tables, high-precision machining, and research on tunnel effects. In positioning technology, traditional positioning devices such as rolling or sliding guides, precision spiral wedge mechanisms, turbine concave wheel mechanisms, gear lever mechanisms, and other mechanical transmission micro displacement actuators constitute the positioning mechanism. Due to the large clearance and friction, ultra precision positioning cannot be achieved. By using piezoelectric actuators combined with flexible hinge amplification mechanisms, the above drawbacks can be overcome to achieve ultra precision positioning at the micro nano level.
Summary
Overall, as the main functional material in modern industrial production, piezoelectric ceramics promote material development through their own advantages and have gained favor from many high-tech industries with numerous advantages. Research in the field of precision/ultra precision is also increasing. With the rapid development of emerging fields and the new demands of economic and social development, there will be higher requirements for the performance of piezoelectric ceramics in the future. For example, high Curie temperature, high electromechanical coupling coefficient and mechanical quality factor, as well as environmental protection, lead-free, composite, and nano piezoelectric ceramics will become the focus of future research.
