Views:2 Author:Site Editor Publish Time: 2019-10-25 Origin:Site
When some dielectrics are deformed by an external force in a certain direction, polarization occurs inside them, and positive and negative opposite charges appear on the two opposite surfaces thereof. When the external force is removed, it will return to the uncharged state. This phenomenon is called the positive piezoelectric effect. When the direction of the force changes, the polarity of the charge changes. On the contrary, when an electric field is applied in the polarization direction of the dielectric, these dielectrics are also deformed, and the deformation of the dielectric disappears after the electric field is removed. This phenomenon is called an inverse piezoelectric effect, or electrostriction. Piezoelectric ceramics are actually a polarized ferroelectric ceramic with piezoelectric effect. It is a new material for information. Piezoelectric ceramics are one kind of functional ceramics.
First, the principle of the piezoelectric effect:
The principle of the piezoelectric effect pzt piezo ceramic is that if a pressure is applied to the piezoelectric material, it generates a potential difference (referred to as a positive piezoelectric effect), and vice versa, a mechanical stress (called an inverse piezoelectric effect) is generated. If the pressure is a high frequency vibration, then a high frequency current is generated. When a high-frequency electric signal is applied to a piezoelectric ceramic, a high-frequency acoustic signal (mechanical vibration) is generated, which is what we usually call an ultrasonic signal. That is to say, piezoelectric ceramics have the function of conversion and inverse conversion between mechanical energy and electrical energy, and this mutual relationship is indeed very interesting.Piezoelectric materials can generate electric fields due to mechanical deformation, or mechanical deformation due to electric field. This inherent mechanical-electrical coupling effect makes piezoelectric materials widely used in engineering. For example, piezoelectric materials have been used to make intelligent structures. In addition to self-supporting capabilities, such structures have functions such as self-diagnosis, self-adaptation, and self-healing, and they play an important role in future aircraft design.
2. Piezoelectric material
The piezoelectric effect of piezoelectric materials piezo disc sensor is due to the special arrangement of atoms in the crystal lattice, which makes the material have the effect of coupling the stress field and the electric field. Depending on the type of material, piezoelectric materials can be classified into piezoelectric single crystals, piezoelectric polycrystals (piezoelectric ceramics), piezoelectric polymers, and piezoelectric composite materials. According to the specific material form, it can be divided into two types: piezoelectric material and piezoelectric film.
3. Piezoelectric single crystal
Piezoelectric single crystals are mostly iron transistors. Also included are quartz, cadmium sulfide, zinc oxide, aluminum nitride and other crystals. These ferroelectric crystals include an oxygen transistor having an oxygen octahedron, such as barium titanate crystal, lithium niobate having a lithium niobate structure, bismuth ruthenate, and strontium ruthenate crystal having a tungsten bronze structure. A ferroelectric transistor is containing a hydrogen bond, such as potassium dihydrogen phosphate, ammonium dihydrogen phosphate, and lead hydrogen phosphate (and lead strontium phosphate) crystals. A barium titanate crystal or the like having a layered structure. At present, the most widely used non-ferroelectric quartz transistor, iron typical pressure transistor lithium niobate and bismuth ruthenate.
4. Piezoelectric polymer
As early as 1940, the Soviet Union discovered that wood was piezoelectric ceramics.piezoelectricity was found in tissues such as ramie, silk bamboo, animal bones, skin, and blood vessels. In 1960, the piezoelectricity of synthetic polymers was discovered. In 1969, it was found that polyvinylidene fluoride after electrodeposition has strong piezoelectricity. Materials having strong piezoelectric properties include PVDF and its copolymers, polyvinyl fluoride, polyvinyl chloride, poly-γ-methyl-L-glutamate, and nylon-11.
5. Piezoelectric composite materials
Piezoelectric composites are piezoelectric materials that are compounded from two or more materials. Common piezoelectric composites are two-phase composites of piezoelectric ceramics and polymers such as polyvinylidene fluoride reactive epoxy. This composite material combines the strengths of piezoelectric ceramics and polymers, has excellent flexibility and processing properties, and has a low density and is easy to match acoustic impedance with air, water and biological tissues. In addition, piezoelectric composites also have a high piezoelectric constant. Piezoelectric composites have a wide range of applications in the fields of medical, sensing, and measurement.
Application of piezoelectric effect of piezo ceramics
1. Manufacturing characteristics
Piezoelectric ceramics are characterized by polarization treatment of ferroelectric ceramics under a direct current electric field to have a piezoelectric effect. Generally, the polarization electric field is 3 to 5 kV/mm, the temperature is 100 to 150 °C, and the time is 5 to 20 min. These three are the main factors affecting the polarization effect. Piezoelectric ceramics with better performance, such as lead zirconate titanate ceramics, have an electromechanical coupling coefficient as high as 0.313 to 0.694.
Piezoelectric 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, acoustic surface devices, electro-optical devices ,igniter and piezoelectric gyro.
2. 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. Earthquakes are devastating disasters, and the source of the earthquake begins in the depths of the earth's crust. It was difficult to predict before, and humans were caught in an embarrassing situation. The sensitivity of the piezoelectric ceramic to the external force makes it possible to sense the disturbance of the air by the flying insects flapping the wings more than ten meters. It can be used to make the piezoelectric seismograph, which can accurately measure the earthquake intensity and indicate the direction and distance of the earthquake. This cannot be a great achievement of piezoelectric ceramics. Piezoelectric ceramics produce a small amount of deformation under the action of an electric field, up to a fraction of a millionth of their own size. Don't underestimate this small change, the precise control mechanism based on this principle--piezoelectric actuator, for Precision instrumentation and mechanical control, microelectronics, bioengineering and other fields are a great boon. 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 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 ability, so that the previous electromagnetic equipment can not be looked back.
Piezoelectric ceramics are new functional electronic materials with high intelligence. With the continuous research and improvement of materials and processes, the application of piezoelectric ceramics is becoming more and more extensive. As a machine, electricity, sound, light, and heat sensitive materials, piezoelectric materials piezo ceramic disc transducer has been widely used in sensors, transducers, non-destructive testing, and communication technologies. Polycrystals are formed by solid phase reaction in various countries around the world. And the general name of ferroelectric ceramics with piezoelectric effect by DC high voltage polarization treatment is a kind of research and development that can attach great importance to mechanical energy to piezoelectric ceramic materials. With the development of high technology, the application of piezoelectric ceramics will become more and more broad. In addition to being used in high-tech fields, it is more about serving people in daily life and creating a better life for people.
Five common applications of piezoelectric ceramics in our daily lives:
1: Application of positive and negative piezoelectric effect
2: Piezoelectric Ceramic Buzzer | Speaker
3: Piezoelectric ceramic pickup
4: Piezoelectric transformer
5: Piezoelectric ceramic igniter
It can be said that although piezoelectric ceramics is a new material, it is quite civilian. It is used in high-tech, but it is more in life to create a better life for people.