Properties Of PSN-PMN-PT Ferroelectric Crystal And The Design Of Medical Piezoelectric Ultrasonic Transducer

As a relevant functional material for the development of excellent performance devices,relaxor-PMN-PT ferroelectric single crystal has widely used in intelligent capture,ultrasonic transducer,precise braking and other fields.However,the application of the PMN-PT crystal in high temperature and large power field is limited due to the low Curie temperature?T_C?and small coercive field?E_C?.The PSN-PMN-PT single crystal developed in our group,with high T_Cand large E_C,overcomes these shortcomings.Although extensive researches have been developed on PSN-PMN-PT,most related investigations were focused on the conventional electrical properties,and the research on other aspects such as optical properties and the tunability of non-contact external field regulation of ferroelectric polarization inversion is deficient.Compared with the conventional electric-controlled ferroelectric,the light-induced crystal is non-contacted,which avoids the introduction of circuits,and it is conducive to the miniaturization and functionalization of the devices.Therefore,we have studied the optical properties,light-induced electrical properties and the reversible reversal of ferroelectric polarization of the PSN-PMN-PT relaxor-ferroelectric single crystal systematically,which provide relevant parameters for the development of a new generation of the multifunctional photoelectric devices and light-induced electrical properties of ferroelectric.Ternary PSN-PMN-PT single crystal has the higher T_Cand more significant E_cthan binary PMN-PT crystal,and the piezoelectric constant in all of them are comparable,which have a certain advantage in the practical application.To further evaluate the potential of the PSN-PMN-PT single crystal,a series of medical ultrasonic transducers were designed and simulated.The main research contents and conclusions are as follows:Optical properties of ternary PSN-PMN-PT single crystal were studied systematically.The refractive index and extinction coefficient were tested,and the parameters of PSN-PMN-PT crystal were obtained by the modified Sellmeier equation and the single-oscillator dispersion relation.The PSN-PMN-PT single crystal has greater transmittance than that of PMN-PT crystal,and it is expected to be used as an optical window material.The polarization in the crystal can improve the transmittance effectively,and the improvement of the transmittance by A.C.poled is more obvious than that of D.C.polarization,which may be related to the decrease of the 71odomain wall and the more orderly structure in crystal.Compared with the PMN-PT single crystal,the addition of Sc³⁺ions causes the blue shift of the absorption edge in PSN-PMN-PT single crystal.And the band-gap energy is different between the PSN-PMN-PT?3.22 e V?and PMN-PT?3.18 e V?,which was calculated by the Tauc equation,indicating that the doping of Sc³⁺ions has modulation effect for the band structure and it give rise to the different optical properties between PSN-PMN-PT and PMN-PT crystal.The effects of light-induced electrical properties of PSN-PMN-PT ferroelectric and the coupling between light and matter were discussed.The electrical properties of ferroelectric can be regulated reversibly by the light?a non-contact external control device?when the laser is turned on,ferroelectric properties increase instantaneously and then maintain stabilization.After the light is removed,the light-induced electrical properties begin to recover,which showed that the light-controlled ferroelectric process is stable,reversible and rewritable.The light-induced PSN-PMN-PT crystal is more sensitive than that of the PMN-PT,and the dielectric properties increment in the unpoled crystal??104%?is more extensive than that of polarized PSN-PMN-PT crystal.Ultra-high light-controlled dielectric properties may be related to the interaction between the electric field component of the light and the electrical charge of the PNRs.We believe that these results will provide some references for the research on the light-induced process of ferroelectric materials in the further.To study the potential application of the PSN-PMN-PT single crystal in excellent performance transducer,the ternary PSN-PMN-PT piezoelectric single crystal medical ultrasonic transducers with a different frequency of 5 MHz and 10 MHz were designed and simulated respectively.The results show that,when the target frequency is 5 Hz and 10 MHz,the center frequency of the piezoelectric single crystal transducers is 4.771 MHz and 9.543MHz,respectively,and all the-6 d B bandwidth at the center frequency are about 80.42%.The results indicate that the ternary PSN-PMN-PT crystal is a potential material for the application of an ultrasonic transducer.