Research On High Performance Piezoelectric Single Crystal High Frequency Ultrasonic Transducer

In ultrasonic imaging systems,the performance of ultrasonic transducers determines the quality of ultrasonic imaging.PMN-PT single crystals have excellent piezoelectric constants,clamped dielectric constant and electromechanical coupling coefficient,which are suitable for the fabrication of high sensitivity,good resolution broad bandwidth and small aperture high frequency ultrasonic transducers.However,the curie temperature and coercivity field of PMN-PT single crystal are relatively low,which have limitations in high temperature and voltage application.Furthermore,the large difference of acoustic impedance between PMN-PT and biological causes serious loss of energy transmission.As for the shortcomings of PMN-PT single crystal,the ultrasonic transducers with high performance piezoelectric single crystal were studied.This paper introduced the basic knowledge of piezoelectric materials and ultrasonic transducers.By introducing piezoelectric effect and piezoelectric equations,piezoelectric vibrator equivalent circuit,varied piezoelectric material and piezoelectric parameters,the working mechanism and performance of piezoelectric material were learned.By introducing the structure composition of transducer,transducer parameters and test methods,the structure and properties of transducer were acquired.The relationship between piezoelectric material performance and transducer performance was expounded.As for the low coercivity field and curie temperature of PMN-PT,Mn doped PIN-PMN-PT high frequency ultrasonic transducer was designed and Fabricated.In this paper,material characterization,PiezoCAD simulation,transducer fabrication and test are completed.The results shown that the doping of Mn and the introduction of PIN system enhance the coercivity field(4.5 kV/cm)and curie temperature(160℃)of piezoelectric material,which brought 42.5 MHz ultrasonic transducer excellent sensitivity(2.178V),effective electromechanical coupling coefficient(0.56)and insertion loss(-20.5dB).As for the high acoustic impedance of PMN-PT,PMN-PT/Epoxy 2-2 composite ultrasonic transducer was designed and fabricated.In this paper,the Comsol simulation design,composite material preparation,PiezoCAD simulation design,transducer fabrication and test are done.The research shown that the acoustic impedance(24.79 MRayl)of the PMN-PT/Epoxy 2-2 composite piezoelectric material was reduced and the electromechanical coupling coefficient(0.59)was improved.The 8.75MHz PMN-PT/Epoxy 2-2 composite ultrasonic transducer exhibits good sensitivity(0.374V)and-6dB frequency bandwidth(35.54%).