Preparation And Piezoelectric Properties Of PZT-based Flexible Composites

With the development of the times,the interaction and communication between human and intelligent equipment is increasing.As a new era group of intelligent equipment,wearable electronic devices with piezoelectric pressure sensors as the core are developing rapidly.However,the piezoelectric pressure sensor based on solid piezoelectric materials has the problems of insufficient flexibility,low sensitivity,poor stability and short service time,which cannot meet the needs of people’s daily life.In view of the above problems,this study designed to prepare flexible piezoelectric composites with traditional solid piezoelectric material-lead zirconate titanate(PZT)as filler,polyimide(PI)and chitosan(CS)as flexible matrix,respectively.The flexible matrix is used to transfer mechanical energy uniformly and dispersedly to PZT filler,and then the potential generated by piezoelectric effect is aggregated in the flexible matrix to achieve flexible and high-performance output.The specific research is as follows:(1)PZT/PI flexible piezoelectric composites were prepared by in-situ polymerization.With the addition of high dielectric constant PZT,the relative dielectric constant of the composites increased from 3.5 to 44.The dielectric loss is always below 0.02 at low frequencies.When the PZT content is 38.6 wt%,the assembled PZT/PI-based piezoelectric pressure sensor(PPS)has the highest output voltage of 9.2 V,showing good piezoelectric output performance.(2)In order to solve the problem of agglomeration and poor dispersibility of lead zirconate titanate in the polyimide matrix,PZT was coated and modified with polydopamine(Pdop).The Pdop@PZT/PI flexible piezoelectric composites were then prepared by in-situ polymerization.Compared with PZT particles,Pdop@PZT is more uniformly distributed in the PI matrix,with more two-phase interfaces and more charge accumulation.Under the action of 10 N mechanical force,the highest output voltage of Pdop@PZT/PI-based PPS is 12.8 V,and the output performance is improved by 39 %.In addition,the sensitivity of PPS is 1.4 V/N,which can maintain a stable output voltage under the action of external forces at different frequencies.After 10000 cycles of periodic impact/release,the open circuit voltage of PPS remained stable.In different limb movements,Pdop@PZT/PI-based PPS can generate sensitive piezoelectric signals.It shows that it has a good application prospect in biological health monitoring and personalized exercise.(3)Using chitosan as a film-forming agent,PZT was deposited in the chitosan matrix by a simple method,thereby forming a flexible piezoelectric composite material with a "brick-mortar stacking structure".With the increase of PZT content,the crystallinity of chitosan increased from 34.3 % to 57.9 %.Under the external force of periodic impact/release,the maximum output voltage of PZT/CS-based PPS is 5.6 V,and the sensitivity is 6.1 V/N,which can maintain a stable output voltage under the external force of different frequencies.After 10000 cycles of periodic impact/release,the open circuit voltage of PPS remained stable,indicating that the device had good stability and durability.After repeated testing for a month of intermittent time,the amplitude of PZT/CS-based PPS signal only shows very small attenuation.In different limb movements,PZT/CSbased PPS will produce different sizes of piezoelectric signals.It shows that it is suitable for collecting different forms of kinetic energy.