Piezoelectric ceramics is a new type functional ceramic material. It is a kind of ceramic material that converts mechanical energy into electrical energy. This feature can be used to make high-precision instruments, which plays a vital role in industrial production. An important topic is an important application of functional ceramics. In 1880, the Curie brothers first discovered the piezoelectric effect on the single crystals. Before 1940, it was known that there were two types of ferroelectrics: the resting salt and the potassium dihydrogen phosphate, which were piezoelectric. After 1940, it was found that BaTiO3 is a ferroelectric with a strong piezoelectric effect. It is a leap in the development of piezoelectric materials. After 1950, the piezoelectric PZT system was discovered, which has a very strong and stable piezoelectric effect and has significant practical progress. After 1970, binary PZT piezo ceramics of piezo cylinder tube transducer with different additives have excellent properties and have been used to make filters, transducers, transformers, and the like. With the development of the electronics industry, the requirements for piezoelectric materials and devices are getting higher and higher. The binary PZT has not been able to meet the requirements of use, so the research and development of ternary, quaternary or even five-element piezoelectrics is superior to material.
About piezoelectric effect, the root cause of the piezoelectric effect of piezo tube piezoceramic transducer is the displacement of the ionic charge in the crystal. When there is no strain, the charge is symmetrically distributed at the lattice position, so the internal electric field is zero. However, when stress is applied to the crystal, the charge is displaced. If the charge distribution is not symmetric, a net polarization occurs, and an electric field is generated, which is a piezoelectric effect. Piezoelectric ceramics are ferroelectric ceramic materials that have a piezoelectric effect after being polarized by DC high voltage. When the crystal is subjected to mechanical force, the surface generates a bound charge, and its charge density is linear with the magnitude of the applied external force. This process of converting from mechanical effect to electrical effect is called positive piezoelectric effect (force→deformation→voltage). The crystal is deformed by the external electric field and has a linear relationship between the two. The process of converting from electrical effect to mechanical effect is called inverse piezoelectric effect (voltage → deformation). Piezoelectric materials of piezo ceramic bimorph 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 are self-diagnostic, adaptive, and self-healing.
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