Preparation And Performance Study Of Bismuth Sodium Titanate Based Piezoelectric Ceramics And It’s Design Of Ultrasonic Transducer

In order to benefit environmental protection and human health,people have gradually attached importance to the development and research of lead-free piezoelectric materials.The lead-free piezoelectric material Bi_0.5Na_0.5Ti O₃（BNT）based piezoelectric ceramics have received widespread attention due to its advantages such as high Curie temperature,high residual polarization,and large electrical strain.The performance of piezoelectric ceramics plays a decisive role in the working ability of the transducer.Considering that lead-free piezoelectric ceramics often lag behind lead-containing piezoelectric ceramics Pb(Zr_1-xTi_x)O₃in terms of performance,in order to achieve good preparation and application of BNT based piezoelectric ceramics,this paper conducted research on key preparation issues and process conditions,new preparation methods,and applications of ultrasonic transducers for BNT based piezoelectric ceramics.The main research content of the full text is as follows:（1）0.94Bi_0.5Na_0.5Ti O3-0.06Ba Ti O₃（BNBT6）piezoelectric ceramics were prepared using conventional solid-state sintering method at a sintering temperature of 1150℃.In response to the problem of poor performance caused by the volatilization of Bi and Na elements during the sintering process of BNT based ceramics,BNBT6 ceramics were prepared by exposure to air,embedding pre synthesized powder,embedding pre synthesized powder,and sintering in an environment with element protection atmosphere to explore the most suitable sintering conditions.The results indicate that sintering with element atmosphere protection and embedding in the pre synthesized powder can solve the problems of easy stoichiometric mismatch and low sintering density of BNBT6ceramics.Therefore,BNBT6 ceramics prepared under these conditions have good piezoelectric properties.（2）BNBT6 piezoelectric ceramics were prepared on steel plate structures using plasma thermal spraying technology.The phase structure,micro morphology,dielectric properties,ferroelectric properties and piezoelectric properties of BNBT6 piezoelectric ceramics prepared by thermal spraying technology were characterized and tested,and its polarization process was optimized and determined.Research has shown that introducing a Ni Cr Al Y bonding layer between thermally sprayed BNBT6 piezoelectric ceramics and steel plates contributes to their structural bonding strength and heat treatment stability;The BNBT6 ceramic produced by plasma thermal spraying is a pure phase with some micro defects and low crystallinity;The relative dielectric constant of BNBT6piezoelectric ceramic prepared by plasma thermal spraying is 110,the dielectric loss is0.9（at room temperature,1 k Hz）,and the residual polarization is 104μC/cm²and coercivity field are 5.8 k V/mm;After appropriate polarization treatment,the piezoelectric coefficient d₃₃is 11 p C/N.（3）The propagation and defect detection of Lamb waves in steel plates were simulated using finite element method.We studied the Lamb wave frequency that is beneficial for steel plate defect detection in specific scenarios,and designed the structure of a comb transducer based on a feasible detection frequency.In addition,the acoustic reception ability of the thermal sprayed piezoelectric ceramic comb transducer integrated on the steel plate was tested.The research shows that it is feasible to apply the BNBT6piezoelectric ceramics made by thermal spraying in the field of Structural health monitoring.