When voltage is applied to piezoelectric ceramics, it will produce mechanical deformation with changes in voltage and frequency. On the other hand, when the piezoelectric ceramic is vibrated, an electric charge is generated. Using this principle, when an electrical signal is applied to a vibrator composed of two piezoelectric ceramics or a piezoelectric ceramic and a metal sheet, so-called bimorph element, ultrasonic waves will be emitted due to bending vibration. On the contrary, when ultrasonic vibration is applied to the piezoelectric bimorph element, an electrical signal is generated. Based on the above effects, piezoelectric ceramics can be used as ultrasonic sensors.

Piezoelectric ceramic wafer is a simple and lightweight electrical device. It is widely used because of its high sensitivity, no magnetic field spreading, no copper wire and magnet, low cost, low power consumption, and easy mass production. Suitable for the transmission and reception of ultrasonic and infrasonic waves, a relatively large area of piezoelectric ceramics can also be used to detect pressure and vibration. The working principle is to use the reversibility of the piezoelectric effect to apply audio voltage on it to emit sound.

The main application range of piezoelectric ceramics

1. Piezoelectric ceramic frequency control device

Piezoelectric frequency control devices include filters, resonators, delay lines, etc. These devices are used in multiplying machines, microcomputers, and color TV delay circuits. Piezoelectric ceramic sheets (piezoelectric vibrators) will produce mechanical vibrations of a certain frequency under the action of external alternating voltage. In general, the amplitude of this vibration is very small, but when the frequency of the applied voltage is the same as the natural mechanical vibration frequency of the piezoelectric vibrator, resonance will be caused, and the amplitude will be greatly increased. At this time, the alternating electric field generates strain through the inverse piezoelectric effect, and the strain generates current through the positive piezoelectric effect, and the electrical energy and mechanical energy are converted to each other to the greatest extent, forming an oscillation. Using the characteristics of piezoelectric vibrator, various filters, resonators, etc. can be manufactured with good frequency stability, high precision, wide applicable frequency range, small size, non-moisture absorption, and long service life, especially in multi-channel communication equipment Zhongneng has improved its anti-interference ability, so it has replaced a considerable part of electromagnetic oscillators and filters, and this trend is still developing.

2. Piezoelectric transducer

The piezoelectric transducer uses the piezoelectric effect and the inverse piezoelectric effect of piezoelectric ceramics to realize the mutual conversion of electric energy and sound energy. Piezoelectric ultrasonic transducer is one of them. It is an underwater acoustic device that transmits and receives ultrasonic waves underwater. Under the action of sound waves, the piezoelectric transducer in the water induces charges at both ends of the transducer. This is the sound wave receiver; if an alternating electric field is applied to the piezoelectric ceramic sheet, the ceramic sheet will become thinner from time to time Sometimes it becomes thicker, and at the same time it vibrates and emits sound waves. This is an ultrasonic transmitter. Piezoelectric transducers are also widely used in the industry for underwater navigation, ocean exploration, precision measurement, ultrasonic cleaning, solid detection, medical imaging, ultrasonic diagnosis, and ultrasonic disease treatment. Another application field of today's piezoelectric ultrasonic transducers is telemetry and remote control systems. Specific application examples include: piezoelectric ceramic buzzers, piezoelectric igniters, and ultrasonic microscopes.

3. Applications in optoelectronics

In addition to piezoelectric effect, piezoelectric ceramics also have pyroelectric effect, photoelasticity, and photoelectric effect. Application devices in this area include: light modulators, light valves, electro-optical displays, optical information storage, image storage and display, and electronically controlled multi-color filters. Transparent ferroelectric ceramics (PLZT) is a valuable new electronic material, which opens up the development of piezoelectric ceramic materials in electro-optical applications. It can be easily processed into products of various sizes and shapes, and the composition properties can be controlled. Features such as wide range and low cost.

4. Piezo Driver

The piezoelectric actuator is made of piezoelectric ceramic material lead zirconate titanate (PZT). If a single-plate piezoelectric ceramic PZT is used, if a 1cm thick PZT wants to obtain a driving displacement of about 10 microns, a voltage of 5KV needs to be applied at both ends. Applying such a high voltage to PZT may cause insulation breakdown and cause mechanical damage. Because the amount of deformation of piezoelectric ceramics has nothing to do with the thickness, people have developed laminated piezoelectric actuators. Make piezoelectric ceramics into very thin slices (0.05 mm piezoelectric ceramic slices can now be manufactured), and connect multiple piezoelectric ceramic substrates mechanically in series and circuit in parallel, and then sintered together production. In this way, a great drive displacement can be obtained by applying a voltage of hundreds of volts to it. In application, people have also developed a flexible hinge structure with small size, no mechanical friction, no gap, and high motion sensitivity for displacement amplification.

5. Micro positioner

Micro-positioners are mainly used for micron and sub-micron precision positioning control, such as the production of optical instruments, fiber optic docking, high-precision three-dimensional micro-motion stage, high-precision machining and tunnel effect research. In positioning technology, traditional positioning devices, such as rolling or sliding guide rails, precision spiral wedge mechanism, turbine-concave mechanism, gear-lever mechanism and other mechanical transmission micro-displacement drives constitute the positioning mechanism, due to the large gap. And friction, so ultra-precision positioning cannot be achieved. The use of a piezoelectric driver combined with a flexible hinge magnifying mechanism can overcome the above shortcomings and achieve ultra-precision positioning at the micro-nano level.

6. Ultrasonic motor

Ultrasonic motor is a new type of motor, which relies on piezoelectric ceramic material as a driver. Under the alternating electric field, ceramics produce expansion and contraction. When a certain type of ultrasonic frequency vibration and fluctuation is excited in the elastic body, the surface of the elastic body uses friction to push the objects in contact with it to move. Generally, it is necessary to convert and recombine various vibration modes so that the piezoelectric motor can change the simple stretching mode of the piezoelectric body into the required driving mode that can be used to generate rotation or linear motion.

7. Active vibration control

Active vibration control uses the intelligent function of piezoelectric ceramics (piezoelectric ceramics can not only sense noise signals, but also send out sound signals with the opposite phase and intensity of the noise signals to counteract noise). It is mainly used for aircraft and diving Active noise control of boats and military vehicles is a very useful high-tech, which will play a very important role in the future military field.

8. Ultrasound medical treatment

The most widely used piezoelectric ultrasonic medical instrument is the B-type ultrasonic diagnostic instrument. In this diagnostic instrument, there is an ultrasonic generating probe made of piezoelectric ceramics. The ultrasonic waves emitted by it are transmitted in the human body. Various tissues in the body have different reflection and transmission effects on the ultrasonic waves. The reflected ultrasonic waves are converted into electrical signals by the piezoelectric ceramic receiver and displayed on the screen. From this, the position, size, and disease of the internal organs can be seen. The B-mode ultrasonic diagnostic apparatus is usually used to check visceral diseased tissues (such as masses, etc.). Piezoelectric ceramics can also be used in ultrasound therapy. When the ultrasonic wave entering the human body reaches a certain intensity, it can cause a certain part of the human body to heat up and vibrate slightly, which can play a massage and massage function to achieve the purpose of treatment, such as the treatment of joints, muscles and other soft tissue injuries and strains. In addition, ultrasound can also be used to pulverize stones in the body, such as gallstones, kidney stones, urinary tract stones and so on.

As the main functional material in modern industrial production, piezoelectric ceramics are favored by many high-tech industries with many advantages, such as electronic technology, aerospace, and biological research. It is believed that with the improvement of related technology, the quality of piezoelectric ceramic materials will be further improved, and be applied in more industries, and promote the development of materials through its own advantages.