Views:0 Author:Site Editor Publish Time: 2020-02-21 Origin:Site
In 1880, the Curie brothers first discovered the piezoelectric effect on a quartz crystal. It reflects the mutual coupling between the elastic and dielectric properties of piezoelectric crystals. When piezoelectric ceramic crystals are deformed by external forces, they generate different amounts of charge on the corresponding surfaces. This phenomenon without an electric field effect is called a positive piezoelectric effect simply because of deformation.
When an electric field of high focusing piezo bowl is applied to a piezoelectric crystal, it is not only polarization, but also deformation. This deformation caused by an electric field is called the inverse piezoelectric effect. The inverse piezoelectric effect is caused by the stress generated inside the crystal when the piezoelectric crystal is subjected to an electric field. This stress is called piezoelectric stress. As a result, piezoelectric strain is generated. Experiments show that all piezo crystals with positive piezoelectric effect must also have anti-piezoelectric effect, and the two are in one-to-one correspondence.
Any medium in the electric field will deform the medium due to induced polarization. This deformation is different from that caused by the inverse piezoelectric effect HIFU ceramic piezoelectric transducer. Dielectrics may cause elastic deformation under the influence of external forces, or deformation under the polarization of external electric fields. The deformation caused by induced polarization is proportional to the square of the external electric field, which is the electrostrictive effect. The deformation it produces is independent of the direction of the external electric field. The deformation caused by the reverse piezoelectric effect is proportional to the external electric field, and the deformation will change when the electric field is reversed (for example, the original elongation can be shortened or the original shortening can be extended).
In addition, whether it is a non-piezoelectric crystal or a piezoelectric crystal, the electrostrictive effect exists in all dielectrics; however, the electrostrictive effect of dielectric piezo ceramic crystals with different structures is different. The anti-piezoelectric effect only exists in piezoelectric disc transducers. Crystals that can generate piezoelectric effects are called piezoelectric crystals. One type of piezoelectric crystal is a single crystal, such as quartz (SiO 2), potassium sodium tartrate (also known as lossal salt, nakc 4h4 o 6 x H2O), bismuth germanate (bi 12 geo 20), and the like. Another type of piezoelectric crystal is called a piezoelectric ceramic, such as barium titanate (batei O3), lead zirconate titanate (Pb (zrxtirx) O3, code PZT), lead zirconate titanate niobium magnesium (Pb added PZT Pb (mg1 / 3n B2 / 3) O3, code PCM), lead antimony manganese zirconate titanate (Pb added Pit code PMS)