Introduction to piezoelectric ceramics -www.ultra-piezo.com

Piezoelectric ceramic, a functional ceramic material capable of converting mechanical energy and electrical energy to each other, is an inorganic non-metallic material. Piezoelectric ceramics are made by the relative stress of the internal positive and negative charge centers under the action of mechanical stress, which causes the opposite ends of the material to have oppositely bound trapped charges, ie piezoelectric effect, and has sensitive characteristics. Ceramics are mainly used in the manufacture of ultrasonic transducers, hydroacoustic transducers, electroacoustic transducers, ceramic filters, ceramic transformers, ceramic discriminators, high voltage generators, infrared detectors, surface acoustic wave devices, electro-optic devices, In addition to being used in high-tech fields, it is used to serve people in daily life and to create a better life for people.



Development History

In 1880, the Curie brothers first discovered the piezoelectric effect of tourmaline and began the history of piezoelectrics.

In 1881, the Curie brothers experiment verified the inverse piezoelectric effect and gave the same positive and negative piezoelectric constants for quartz.

In 1894, Voigt pointed out that crystals of only twenty point groups without symmetry centers are likely to have a piezoelectric effect. Quartz is a representative of piezoelectric crystals, and it has been applied.

In the First World War, Curie's heir, Lang Zhiwan, first used the piezoelectric effect of quartz to make an underwater ultrasonic detector for detecting submarines, thus uncovering the chapter on the history of piezoelectric applications.

BaTiO3 ceramics were discovered in the Second World War, and piezoelectric materials and their applications have made epoch-making progress.

In 1946, the Institute of Insulation of the Massachusetts Institute of Technology found that a DC high-voltage electric field was applied to the barium titanate ferroelectric ceramics, so that the spontaneous polarization was preferentially oriented along the direction of the electric field, and the residual polarization was maintained after the electric field was removed. With the piezoelectric effect, piezoelectric ceramics were born.

In 1947, Roberts applied high voltage on BaTiO3 ceramics to obtain the voltage of piezoelectric ceramics. Subsequently, Japan actively developed ultrasonic transducers, high-frequency transducers and pressure sensors using BaTiO3 piezoelectric ceramics. Applications of various piezoelectric devices such as filters, resonators, etc., have been conducted until the mid-1950s.

In 1955, B. Jaffe et al. found that PZT piezoelectric ceramics, which are superior in piezoelectricity to BaTiO3, have greatly advanced the application of piezoelectric devices. Some applications that are difficult to be practical in the BaTiO3 era, especially piezoelectric ceramic filters and resonators, have been rapidly put into practical use with the advent of PZT, and SAW filters, delay lines, and oscillators have been applied. The device was also implemented in the late 1970s.

Piezoelectric ceramic properties

Piezoelectric ceramics have sensitive characteristics and can convert extremely weak mechanical vibration into electrical signals, which can be used in sonar systems, weather detection, telemetry environmental protection, household appliances, etc. The sensitivity of the piezoelectric ceramic to external forces makes it possible to sense the disturbance of the air by the flying insects flapping their wings more than ten meters. It can be used to make piezoelectric seismographs, which can accurately measure the earthquake intensity and indicate the direction and distance of the earthquake. This cannot but be said to be a great achievement of piezoelectric ceramics.

Piezoelectric ceramics produce small deformation variables under the action of an electric field, up to a fraction of a millionth of their own size. Don't underestimate the slight change, the precise control mechanism based on this principle--piezoelectric actuator, for Precision instrumentation and mechanical control, microelectronics, bioengineering, etc. are all great news.

Frequency control devices such as resonators and filters are the key devices that determine the performance of communication devices. Piezoelectric ceramics have obvious advantages in this respect. It has good frequency stability, high precision and wide applicable frequency range, and is small in size, non-hygroscopic, and long in life. Especially in multi-channel communication equipment, it can improve the anti-interference, so that the previous electromagnetic equipment can not be expected to face it. The fate of substitution.

Piezoelectric ceramic application

1. Sound Converter Sound Converter is one of the most common applications. Piezoelectric ceramics can be used as sound transducers for pickups, microphones, earphones, buzzers, ultrasonic depth detectors, sonar, and ultrasonic flaw detectors. For example, a buzzer on a children's toy is a current that vibrates through the inverse piezoelectric effect of the piezoelectric ceramic, and emits a sound that can be heard by the human ear. Piezoelectric ceramics can generate vibrations of different frequencies through the control of electronic circuits, thereby emitting various sounds. For example, an electronic music greeting card converts an AC audio signal into a sound signal through an inverse piezoelectric effect.



2, ultrasonic transducer is suitable for ultrasonic welding equipment and ultrasonic cleaning equipment, mainly using high-power emission type piezoelectric ceramics, ultrasonic transducer is a device that can convert high-frequency electrical energy into mechanical energy, ultrasonic transducer As an energy conversion device, its function is to convert the input electrical power into mechanical power (ie, ultrasonic waves) and then pass it out, while it consumes a small amount of power itself.

3. Piezoelectric lighter A new type of electronic lighter used on gas stoves is made of piezoelectric ceramics. As long as the ignition button is pressed with a finger, the piezoelectric ceramic on the lighter can generate a high voltage, form an electric spark and ignite the gas, which can be used for a long time. Therefore, the piezoelectric lighter is not only convenient to use, safe and reliable, but also has a long service life. For example, a lighter made of a lead titanate piezoelectric ceramic can be used for more than one million times.

4. After the nuclear tester with anti-nuclear goggles carries the goggles made of transparent piezoelectric ceramics, when the optical radiation generated by the nuclear explosion reaches a dangerous level, the piezoelectric ceramic in the goggles turns it into a transient high voltage. Electricity, in 1/1000 s, can reduce the light intensity to only 1/10000. When the dangerous light disappears, it can return to its original state. The goggles are simple in structure and only a few tens of grams in weight. They are easy to carry on the anti-nuclear eye protection helmet.

5, piezoelectric detonator Since the British World War I invented the tank in the First World War, and the first use in the French Somme River battle and hit the German army, the tank in the battles to show their talents. However, in the 1960s and 1970s, due to the invention of anti-tank weapons, the tank lost its former glory. The warhead is equipped with piezoelectric ceramics, which can transform the powerful mechanical force at the time of collision into an instantaneous high voltage, and sparks to explode the explosive.

6, sonar In the naval battle, the most difficult to deal with is the submarine, it can snorkel under the sea for a long time, God unconsciously sneak attack on the port, the ship, so that the enemy is a big headache. How to find enemy submarines? It is not possible to use the radar, because the electromagnetic waves will be attenuated sharply in the sea water, and the signal cannot be transmitted effectively. The submarine is detected by the sonar ------ underwater ear. Piezoelectric ceramics are materials for making sonar. They emit ultrasonic waves, which are reflected back by the submarine. After being received and processed, the position and distance of the enemy submarine can be measured.

Piezoceramic PZT Material

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