Signs You Need Help With Piezoelectric Transducer

The bismuth layered structure compound of ultrasonic receiver transducer was first discovered by Aurivillius in 1949. Then its unique crystal structure and high Curie temperature of ultrasonic transducer application aroused widespread concern, this system has done in-depth study. The chemical formula of bismuth layered ceramic can be expressed as (Bi2O2) 2+ (Am-1BmO3m + 1) 2-, which is formed by (Bi2O2) 2+ and perovskite layers (Am-1BmO3m + 1) Arrangement, A bit of 12 coordination with 1 ~ 4 valences or the compound between them, such as: K +, Na +, Ca2 +, Pb2 +, Ln3 +, Bi3 +, U4 + and so on; B position for octahedral coordination of ions Or a combination thereof, such as: Fe3 +, Cr3 +, Ga3 +, Ti4 +, Zr4 +, Nb5 +, Ta5 +, etc. m is an integer corresponding to the number of octahedral layers in the perovskite layer, typically between 1 and 5. Curie temperature PZT material piezo is TC = 790 ℃, is the more common and more studied bismuth layered piezoelectric ceramics. ultrasonic piezoelectric cylindergenerally have a relatively low dielectric constant, sintering temperature and aging rate, as well as excellent insulation resistance and withstand voltage characteristics, very high Curie temperature and significant anisotropy of the electromechanical coupling coefficient, which piezoelectric sensor circuit make them suitable for use as high temperature , Piezoelectric materials used in high-frequency occasions.However, due to the low symmetry of the bismuth layered structure and its plate-like crystal characteristics, the coercive field of the piezoelectric tube sensor is very large and very difficult to polarize, which usually needs to be carried out under high temperature. On the other hand, Limit, so the piezoelectric activity is very low, the piezoelectric coefficient d33 generally do not exceed 20 pC / N. In order to improve the piezoelectric properties of bismuth layered ceramic, it needs to be modified. There are two commonly used methods: process improvement and doping substitution. The purpose of the process improvement is to hope that the growth orientation of the crystal grains can be controlled by some special processing to obtain the textured ceramic. Generally there are two ways to get a certain texture of the ceramic: one is a special heat treatment process, such as hot-casting method and hot pressing, etc., this method is mainly through the grain boundary dislocation movement and grain boundaries Of the slip, so that the crystal grain to achieve directional orientation, and the other is through the template crystal growth method, the molten salt obtained by the method of certain orientation of the crystal grains as a template dispersed into the matrix, the use of additional driving force to grain Oriented growth according to the orientation of the template.