Study On Condensed Structure And Electrical Properties Of P(VDF-TrFE)synthetic Via A Hydrogenation Process

P(VDF-TrFE)is a kind of excellent ferroelectric and piezoelectric materials,which can be widely used in electromec.hanical sensors,actuators,storage and other transducer devices.The ferroelectric and piezoelectric properties of P(VDF-TrFE)are closely related to their crystallization properties.Only the ?-form P(VDF-TrFE)exhibits excellent piezoelectric and transducing properties.The formation of ?-form P(VDF-TrFE)is affected by man.y factors.In addition to the single composition of VDF and TrFE,sample preparation conditions are important factors.The preparation of P(VDF-TrFE)is usually carried out by conventional copolymerization and indirect hydrogenation.Compared with the conven,tional P(VDF-TrFE),the crystallinity of P(VDF-TrFE)obtained by dehydrochlorination is less studied.Moreover,there are few studies on the relationship between hy'drogenated P(VDF-TrFE)crystals and their electrical properties.In view of the tendency of hydrogenated P(VDF-TrFE)to replace the traditional P(VDF-TrF E)and tensile PVDF piezoelectric fiilms,it is necessary to study the hydrogenation of P(VDF-TrFE)ferroelectric and its piezoelectric properties.And phase transition dependence.In response to the above objectives,this paper has carried out the following work:1)Using the environmentally friendly controlled radical chain transfer(ATRCT)method,the industrial P(VDF-CTFE)with CTFE unit content of 20 mol%was used as raw material to synthesize the total hydrogenated P(VDF-TrFE).TrFE molar content is 20%.On this basis,P(VDF-TrFE)films with different heat treatment conditions were prepared by solution casting method under different thermal conditions.2)The crystallization performance of the P(VDF-TrFE)film with different heat treatment conditions was tested.The ? crystal form can be confirmed from XRD in the diffraction peak at 20= 19.70°and the endothermic peak in DSC.It is proved that P(VDF-TrFE)with TrFE content of 20 mol%is single crystal form under different temperature service conditions.It was found by using POM that the grain size was small.3)The dielectric properties of P(VDF-TrFE)with TrFE unit content of 20 mol%under different preparation conditions were characterized by dielectric thermogram.The P(VDF-TrFE)film with different heat treatment conditions showed that the dielectric constant increased with the increase of temperature,and the dielectric loss decreased with the increase of frequency.The film annealed at 200? had a dielectric constant of 70.3 at a frequency of 100 Hz and a dielectric loss of 0.07.Moreover,the dielectric thermogram data indicates that the ferroelectric P(VDF-TrFE)film has a ferroelectric-paraelectric phase transition(F-P)temperature of 80-100?,which is consistent with the DSC results.4)Different thickness P(VDF-TrFE)films were prepared by changing the solution concentration.The ferroelectricity of different films was tested by hysteresis loop,and the relationship between polarization mode and service conditions was investigated.It is found that at very low temperatures,the dipole is bound and cannot be turned over.As the test temperature increases,the dipole flip increases and the contribution increases.The maximum electrode polarization(Pm)of P(VDF-TrFE)with TrFE unit content of 20mol%reached 12.25 ?C/cm2 under electric field of 200MV/m after polarization,and the residual polarization(Pr)was 9.54?C/cm2.The direction piezoelectric constant(d33)reached-22pC/N.Finally,the electromechanical coupling coefficient of P(VDF-TrFE)with different thicknesses was characterized and simulated by electrical impedance spectroscopy.It was found that the electromechanical coupling coefficient of hydrogenated P(VDF-TrFE)reached 0.26-0.34,close to the copolymerization sample,and it decreases as the thickness increases.The above results show that the hydrogenated P(VDF-TrFE)piezoelectric film has a wide source of raw materials and a green preparation process,and its ferroelectric,piezoelectric and electromechanical coupling performance is close to the conventional P(VDF-TrFE)film.Therefore,hydrogenated P(VDF-TrFE)films are expected to replace conventional P(VDF-TrFE)and PVDF piezoelectric films,playing an important role in transducer and memory devices.