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10 Minutes to Quickly Understand Piezoelectric Ceramics

Views:130     Author:Site Editor     Publish Time: 2020-06-28      Origin:Site

Piezoelectric ceramics are functional ceramic materials that convert mechanical energy and electrical energy. In addition to piezoelectricity, piezoelectric ceramics also have dielectric properties, elasticity, etc., and have been widely used in medical imaging, acoustic sensors, acoustic transducers, ultrasonic motors, and so on. Weifang Jude Electronic Co. Ltd is a manufacturer and supplier of high-quality piezoelectric ceramics for a multitude of electrical functions.


piezoelectric ceramic


Principle


Usually, ceramics are composed of fine crystals. Each crystal consists of a positively or negatively charged atom. Most ceramics have a well-balanced positive and negative charge. However, even under natural conditions, some dielectric ceramics called "ferroelectrics" produce unbalanced positive and negative charges in the crystal, resulting in charge shift (spontaneous polarization). In general, ceramics appear to have a well-balanced positive and negative charge. However, with the application of a high DC voltage, the polar axes generated by spontaneous polarization are aligned in a uniform direction, even if the voltage is removed. The process of aligning the polar axes of spontaneous polarization is called the polarization process.

If the polarization process is applied to ferroelectric ceramics, piezoelectric ceramics are produced. When an external voltage is applied to the piezoelectric ceramic, the centers of the positive and negative charges in the ceramic are respectively attracted or repelled by the external charges, causing the ceramic to expand or contract.

In other words, the piezoelectric material expands or contracts when subjected to a voltage, and generates a voltage when subjected to pressure. As described above, piezoelectric ceramics realize mutual conversion between electric energy and mechanical energy by utilizing the polarization of crystals.


History


The property of converting mechanical energy into electrical energy and converting electrical energy into mechanical energy is called piezoelectric. The piezoelectric effect discovered in 1880 caused crystal materials (such as quartz) to generate charge when compressed, twisted or pulled. Vice versa, the crystal material compresses or expands when a voltage is applied.

In the 1950s, barium titanate was the first piezoelectric ceramic material to be used, mainly as an ultrasonic transducer element in fish finder.

By the late 1950s, the discovery of lead zirconate titanate (PZT) piezoelectric ceramic materials in the United States has greatly advanced the application of piezoelectric devices, and PZT has become a popular piezoelectric ceramic.


piezoelectric ring


Characteristic


1. Dielectric

The dielectric properties of piezoelectric ceramics reflect the degree of response of ceramic materials to external electric fields. Piezoelectric ceramic components for different purposes have different dielectric constant requirements for piezoelectric ceramics. For example, an audio component such as a piezoelectric ceramic speaker requires a ceramic having a large dielectric constant, and a high-frequency piezoelectric ceramic component requires a material having a low dielectric constant.


2. Elastic property

The elasticity of piezoelectric ceramic is a parameter that reflects the relationship between the deformation of the ceramic and the force. Piezoelectric ceramic materials, like other elastomers, follow Hooke's law. For piezoelectric bodies, the value of the spring constant is related to electrical boundary conditions due to the presence of piezoelectricity. Elastic coefficient


3. Piezoelectricity

The largest characteristic of piezoelectric ceramics is piezoelectricity, including positive piezoelectricity and reverse piezoelectricity.

Positive piezoelectricity refers to the fact that some dielectrics are subjected to mechanical external forces, and the positive and negative charges in the medium are relatively displaced to cause polarization, which leads to the oppositely bound charges on the two ends of the dielectric.

When an external electric field is applied to a piezoelectric dielectric, the positive and negative charge centers inside the dielectric are relatively displaced and polarized, whereby the displacement causes the dielectric to deform. This effect is called inverse piezoelectricity.


4. Other features

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 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.

piezo ceramic ring

Manufacturing process


The process is as follows: ingredients - mixing and grinding - pre-burning - secondary grinding - granulation - molding - plasticizing - sintering into porcelain - shape processing - by electrode - high-pressure polarization - -Aging test.


1. The ingredients

Pre-treatment of the material, in addition to impurities and tides. The raw materials are then weighed according to the formulation ratio, and a small number of additives are placed in the middle of a large number of materials.


2. The mixing and grinding

The purpose is to uniformly mix and grind the various raw materials, for the pre-burning. Dry or wet grinding is generally used. The dry grinding method can be used in small batches, and the method of the agitating ball mill or jet milling can be used in large quantities, which is more efficient.


3. Pre-burning

The purpose is to react to various raw materials at high temperatures to synthesize piezoelectric ceramics. This process is important and directly affects the sintering conditions and the performance of the final product.


4. Secondary fine grinding

The purpose is to uniformly mix and grind the pre-fired piezoelectric ceramic powder to lay a good foundation for the uniform performance of porcelain.


5. Granulation

The purpose is to make the powder form a high density of particles with good fluidity. Manual methods are less efficient and can be spray granulated. This process involves the addition of a binder. 6. Molding: The purpose is to press the finished material into the required preformed size blank.


piezoelectric components


6. Distorting

The purpose is to remove the binder added during granulation from the blank.


7. Sintering into porcelain

The blank is sealed and sintered into porcelain at high temperatures.


8. Shape processing

The polished product is polished to the required finished product size.


9. Electrode

Place a conductive electrode on the desired ceramic surface. The general methods are silver layer infiltration, chemical deposition, and vacuum coating.


10. High-voltage polarization

The ceramic internal charge is aligned so that the ceramic has piezoelectric properties.


11. Aging test

After the ceramic performance is stable, the indicators are tested to see if the expected performance requirements are met.


Application


In sensors, piezoelectric ceramic materials convert pressure into electrical signals. Therefore, they can be used in the manufacture of ceramic filters, ceramic transformers, ceramic discriminators, high voltage generators, infrared detectors, Pilot ignition device, and piezoelectric gyros.

In Sonic and ultrasonic actuators, piezoelectric ceramic materials convert the voltage into vibration. Therefore, they can be used in various fields, such as ultrasonic equipment for eyeglass cleaning machines, cosmetic equipment for facial massage, transmitters and receivers for sonar, and the like.

In addition to being used in high-tech fields, piezoelectric ceramic materials are more in everyday life. From radio parts to lighter ignition systems, piezoelectric parts have become standard in a variety of applications. Piezoelectric ceramics are also integrated into electronic components in various household appliances or industrial products to create a better life for people. Piezoelectric ceramics are already an integral part of our lives, and the market for such materials continues to expand.


Weifang Jude Electronic Co. Ltd is a manufacturer and supplier of high-quality piezoelectric ceramics for a multitude of electrical functions. If you have any needs, please contact us.

piezo components

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