Bismuth layered piezoelectric ceramics

Finding a piezoelectric ceramic material that is comparable to PZT ceramic without lead .which piezoelectric plates crystal becomes an urgent need in the field of electronic materials. At present, the research focuses mainly on two main categories: bismuth-containing (B i2O2) piezoelectric ceramics and bismuth sodium titanate (NaxBix) (BNT) with perovskite structure. Electric ceramic is composed of two-dimensional perovskite and (Bi2O2) layers alternately arranged from each other and its special layered structure determines the following characteristics: low dielectric constant, high curie temperature, electromechanical coupling coefficient , rectangle piezo sensor has high resistivity, low aging rate, large dielectric breakdown strength and low sintering temperature, etc. These characteristics determine that piezo ceramic is particularly suitable for high temperature and high frequency applications, thus solving the problem of high power resonance PZT piezoelectric ceramics However, the bismuth layered piezoelectric ceramics have their own disadvantages: one piezoelectric electricity generation is that the coercive field (E c) is too high, which is not conducive to polarization; the other piezoelectric activity is low. In order to overcome these two kinds of defects, Mainly piezo harvesting plate is used for high temperature polarization, because the coercive field decreases with increasing temperature and doping modification, Li and other 0.94TiO3 join La, Nb, the coercive field decreased, the piezoelectric activity has been greatly improved, This material is suitable for the manufacture of piezoelectric filters, oscillators, piezoelectric resonators and the like.In addition, performance improvements of piezo plates transducer can be achieved through process improvements such as grain-oriented technique. which ncrease the anisotropy of bismuth-clad transistors. Bismuth sodium titanate TiO3 (BNT) is also the hotspot of lead-free ceramics. It was first discovered in 1960 and has a perovskite structure. The same sodium bismuth titanate also has low piezoelectric activity, large coercive field and so on. At present, bismuth titanate sodium is modified mainly by adding various perovskite structure dopants. Wang (B i0. 5N a0. 5) was added to the material fraction of 0.5% CeO2 and 0.75% of La2O3 by conventional sintering and found that the piezoelectric ceramics .Piezoelectric tubes for micro-actuator improved the properties of d33 at 1kH z resonance frequency , Dielectric loss tan δ = 2.0%, by X-ray diffraction found that CeO2 and La2O3 dispersed in the crystal lattice during sintering, it does not affect the performance of the piezo ceramic. BaTiO3 is the earliest material that found a lead-free piezoelectric ceramics.