Performance Control Of High Performance Piezoelectric Single Crystal Materials And Medical High Frequency Ultrasonic Transducer

Ultrasound imaging technology has the advantages of non-invasive,real-time,convenient and economical,and is widely used in the field of medical imaging.At present,conventional ultrasonic devices are mostly low-frequency and low-resolution,and there are many limitations in applications such as ophthalmology and intravascular ultrasound imaging.New medical high-frequency ultrasound technology with higher resolution has rapidly developed,and there is an urgent need for high-performance piezoelectric materials for high-frequency ultrasonic transducers operating at frequencies from 20 to 80 MHz.In this paper,the performance of the(K_xNa_1-x)NbO₃（KNN）single crystal material with the best comprehensive performance in the current lead-free system is controlled,and the high-voltage electrical performance lead-free piezoelectric single crystal element is prepared and the operating frequency is up to 50 MHz.In order to overcome the shortcomings of the traditional method of preparing piezoelectric composite materials,lithography-deep reactive ion etching micro-nano processing method is used to prepare0.5mol%MnO₂-0.3Pb(In_1/2Nb_1/2)O₃-0.4Pb(Mg_1/3Nb_2/3)O₃-0.3PbTiO₃（Mn:PIMNT）based on high-performance relaxation ferroelectric single crystal was explored for its process parameters and control methods.The main research contents and results are as follows:In order to obtain environmentally friendly lead-free piezoelectric materials with high-voltage electrical properties,this paper uses Mn ion doping and polarization,annealing and other processes to optimize the performance of KNN single crystal.It was found by XRD,heating Raman and Piezoresponse force microscopy that Mn:KNN piezoelectric single crystal is a pure perovskite structure,which is an orthogonal phase at room temperature.Therefore,Mn:KNN piezoelectric single crystal in（001）direction is used.The electrical properties of the crystal were characterized and large d₃₃ of 300 pC/N,k_t of 0.64,and frequency constant N_t of 3210kHz·mm was obtained.Based on the prepared high performance Mn:KNN piezoelectric single crystal element,the high frequency ultrasonic transducer with simulated operating frequency of 50 MHz was simulated by PiezoCAD software,prepared according to the simulation results,and then prepared by pulse echo method.Mn:KNN lead-free piezoelectric single crystal high-frequency ultrasonic transducer,the center frequency,frequency range,pulse wavelength and bidirectional insertion loss of the ultrasonic transducer are 51.8 MHz,33.84⁶9.91 MHz,186 ns,-91.2 dB,respectively.The experimental results agree well with the theoretical simulations.The transducer bandwidth is as high as 70.2%,which is nearly 30%higher than the bandwidth of the existing conventional lead-free piezoelectric material ultrasonic transducer.The prepared high-frequency ultrasound transducer was used to test the intravascular imaging of small animal heart arteries,and the imaging effect was good,showing that it has excellent application prospects in the field of medical ultrasound imaging.Using high-voltage electrical properties of Mn:PIMNT single crystal and lithography-deep reactive ion etching micro-nano processing technology to prepare1-3 composite materials.The prepared ultrasonic transducer operating frequency can exceed the limit of 20 MHz.The verticality is up to 85°,the etching depth is about20μm,and it has been included in photolithography,electroplating,Specific parameters and regulation laws of key processes such as deep etching.In this paper,the performance of KNN-based lead-free piezoelectric single crystals is controlled to prepare high-voltage electrical properties of Mn:KNN lead-free piezoelectric single crystal components,simulating and actually preparing high frequency environment friendly with operating frequency up to 50 MHz.Type of medical ultrasonic transducer;in order to overcome the drawbacks of traditional methods for preparing 1-3 composite materials,lithography-deep reactive ion etching micro-nano processing technology combined with high-voltage electrical properties of Mn:PIMNT single crystal to prepare 1-3 composite Piezoelectric material.It lays a solid foundation for the development of a new generation of high-frequency medical ultrasound technology in China,and provides materials for the development of high-frequency medical ultrasonic transducers.