Application of piezoelectric materials and piezoelectric effects

Views: 2 Author: Site Editor Publish Time: 2019-09-24 Origin: Site

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The rapid development of the world economy has led to a sharp increase in energy consumption. With the depletion of non-renewable energy sources and the protection of the environment, countries are vigorously developing sustainable clean energy. Clean energy such as light, wind and solar energy is gradually causing
The piezoelectric effect can be used for pressure power generation, because it has the advantages of simple structure, no heat, no electromagnetic interference, no pollution, easy to achieve miniaturization and integration, and with the improvement of piezoelectric properties of piezoelectric materials piezoelectric disc transducer andnew power electronics. The usage of devices can meet the power requirements of low-energy products and become one of the hotspots of current research.
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1 Principle of piezoelectric effect
When some dielectrics are deformed by external forces in a certain direction, while internal polarization occurs, positive and negative charges appear on two opposite surfaces of the piezo crystal. This phenomenon is called piezoelectric effect. The piezoelectric effect is divided into a positive piezoelectric effect and an inverse piezoelectric effect. The so-called positive piezoelectric effect refers to the effect of the medium being dielectricized by the action of mechanical stress and charging the surface. Conversely, when an electric field is applied outside the crystal, the crystal affected by the electric field will undergo mechanical deformation, called the inverse piezoelectric effect.

2 Piezoelectric material classification
Piezoelectric materials have experienced several milestones in quartz crystals, piezoelectric ceramics, piezoelectric polymers, and piezoelectric composites. The main types of piezoelectric materials are briefly introduced.

1) Piezoelectric ceramics crystal.
Piezoelectric crystals are the materials used in the early piezoelectric effect, mainlyquartz crystal (SiO2), water-soluble piezoelectric crystal (potassium sodium tartrate) and lithium niobate crystal. Due to the stable performance of piezoelectric single crystal, the cost is high. Only for standard instruments or sensors with high accuracyrequirements. The development of piezoelectric ceramic technology has gradually replaced the trend of the above materials. However, in recent years, scholars from various countries have done a lot of work for the development of new crystalline piezoelectric materials. At present, a single crystal piezoelectric piezo ceramic disc with a maximum of 2600pc/N and a k33 of up to 0.95 has been developed, and its energy storage density can reach 130J/kg, which is more than 10 times of the storage density of piezoelectric ceramics. Research on the production process of piezoelectric materials has been carried out and the success of mass production will certainly expand the further application of piezoelectric materials.

2) PbTiO3 based piezoelectric material.
PbTiO3 (referred to as PT) piezoelectric materials have been widely used in the fabrication of high frequency and high temperature piezoelectric ceramic components. At present, some researches have been carried out on this material, mainly in the preparation of PbTiO3 nanopowder, including the production of raw materials, production methods and manufacturing processes. The diversity of raw materials and the continuous updating of manufacturing processes have made the performance of PbTiO3 continuously improved. At present, the material has been widely used in transducer, ultrasonic and industrial nondestructive testing.

3) Piezoelectric ceramics.
Piezoelectric ceramics are artificially fabricated polycrystalline piezoelectric materials . The development of processing technology has enabled the size of piezoelectric ceramics to be reduced to sub-micron, so that the substrate can be made thinner and fine-grained piezoelectric ceramics appear. This material increases the array frequency and reduces the array loss, but it also reduces the effects of the piezoelectric effect. The development of nanotechnology has improved the piezoelectric effect of fine-grained piezoelectric ceramics, and its piezoelectric effect is comparable to that of coarse-grain piezoelectric ceramics. At present, the research and development of piezoelectric ceramic materials is of concern to all countries.

4) High polymer composites.
Research on piezoelectric polymer composites began in the early 1970s. From the perspective of use, piezoelectric polymers can be classified into piezoelectric plastics, piezoelectric rubbers, piezoelectric resins, piezoelectric high polymer composites, and synthetic polypeptides. Piezoelectric plastics are based on synthetic or natural piezoelectric polymers, which can be molded during processing, while the product can finally maintain a constant shape of piezoelectric polymer. Piezoelectric rubber isa general term for highly elastic piezoelectric polymers. In general, piezoelectric polymers with large elongation, tensile strength and resilience in the temperature range of -130 ° C to 150 ° C are all pressed in the processed piezoelectric polymer.Electric rubber, specifically can be divided into piezoelectric silicone rubber, piezoelectric fluororubber and so on. Piezoelectric resin is a semi-solid, solid or pseudo-solid amorphous piezoelectric polymer, transparent or translucent, piezoelectric piezoelectric resin such as nylon-11, amorphous polar alternating copolymer of cyanide - Vinyl acetate, polypropylene, polycarbonate, and the like. Then developed is a piezoelectric high polymer composite material, which is composed of two or more differentpiezoelectric materials through physical mixing or chemical grafting, etc., which are “length-to-length” and have better performance than any of them. A material, PZT-epoxy resin, ceramic-polymer piezoelectric material is more commonly used. There are no strict limits for piezoelectric polymers, whether they are derived from the composition of the material or the form of the finished product.

3 Application of piezoelectric effect
Piezoelectric effect technology has been widely used in the fabrication of various transducers, actuators, and sensors. A typical example of the application of piezoelectric effects in transducers is the application of electrical signal time delays. In the past, the delay line fabricated by the transmission line is large in volume, and the signal loss is large during transmission. The piezoelectric transducer is attached to the transmitting transducer and the receiving transducer on a solid medium, and the electrical signal is transmitted through the inverse piezoelectric effect. The signal is converted into an acoustic signal and propagated in a solid medium. After a periodof time, the acoustic signal is converted into an electrical signal by the receiving transducer through the positive piezoelectric effect, and the signal delay task is completed. Since the velocity of sound waves in a solid medium is five orders of magnitude slower than that of an electromagnetic wave, signal delay can be achieved with only a small solid medium. The delay line made by the piezoelectric transducer has the characteristics of small volume, light weight, stable performance, and the like, and is relatively easy to manufacture. Various actuators can be made using theinverse piezoelectric effect. Piezoelectric actuators can be divided into rigid displacement drivers and resonant displacement drivers according to different driving methods. Piezoelectric actuators do not require a transmission mechanism and achieve high displacement control accuracy. At the same time, the response speed is fast, there is no mechanical anastomosis gap, voltage follow-up displacement control can be realized, and the power output is large while the power consumption is low. China has achieved outstanding results in this field, such as piezoelectric ultrasonic motors, micro-robots, and tiny grippers. Various sensors can be fabricated using the piezoelectric effect, such as piezoelectric pressure sensors, ultrasonic sensors, and piezoelectric acceleration sensors.

Piezoelectric accelerometers are characterized by their simple structure, small size, light weight and long service life. They have been widely used in vibration and shock measurement of aircraft, automobiles, ships, bridges and buildings, especially aviation and It has its special status in the field of aerospace. Piezoelectric sensors can also be used to measure internal combustion pressure and vacuum, and are used in military industry and biomedical measurements. In addition, piezoelectric measuring technology can also be used to make various measuring instruments such as piezoelectric gyro and piezoelectric flowmeter, aswell as discriminators, piezoelectric oscillators, transformers, filters, etc., which are produced in production, life, scientific research and national defense. piezo disc

With its unique advantages, piezoelectric effect HIFU ceramics transducer technology has been widely used in today's growing energy demand. In this paper, piezoelectric materials are introduced from four aspects: piezoelectric crystal, PbTiO3 piezoelectric material, piezoelectricceramic and high polymer composite. The application of this technology in transducers, actuators and sensors is given. I believe that the development of piezoelectric technology will bring us a better tomorrow. To ensure the quality of the construction, and to reduce the occurrence of safety accidents during the construction process. The introduction of new technologies into the construction process can not only improve the construction quality, but also improve the safety of the construction process, such as the use of live online testing equipment technology.

4) Strengthen the maintenance of construction equipment.
In the long-term use of electric power construction equipment, it will be affected by industrial pollution and environmental pollution. In order to reduce these effects, it is necessary to prepare accordingly before construction. For example, pre-corrosion treatment of insulated wires before construction, or selection of insulators with strong anti-pollution ability, and regular maintenance and maintenance of equipment.