Preparation And Properties Of PVDF Based 1-3 Piezoelectric Composite

Traditional 1-3 type piezoelectric composite materials are mostly filled with epoxy resin base with small curing volume shrinkage and no piezoelectricity.The polymer phase cannot affect the inorganic piezoelectric body from a microscopic perspective to enhance the piezoelectric effect of the composite system.Therefore,in this paper,piezoelectric polymer polyvinylidene fluoride-trifluoroethylene P(VDF-TrFE)or ?-phase vinylidene fluoride PVDF is used as a filled,oriented novel relaxation ferroelectric single crystal lead niobate-titanate Lead Pb(Mgi/3Nb2/3)O3-PbTiO3(hereinafter referred to as PMN-PT)is an inorganic piezoelectric body,and a 7-hole and 12-hole structure PMN-PT/PVDF,PMN-PT/P are prepared by cutting hot pressing method(VDF-TrFE)1-3 piezoelectric composite materials;then research and explore the composition,performance,reverse polarization,space size(spatial distribution,orientation,aspect ratio)of each phase in the composite structure,and design according to the parameters Porous mold,research process,Piezoelectric composite sheets with thicknesses of 0.9 mm,1.2 mm,1.5 mm,1.8 mm,and 2.1 mm were prepared;finally using piezoelectric tester,impedance analyzer and ferroelectric tester.The change law of dielectric,ferroelectric,piezoelectric and strain properties is compared and analyzed.The research results obtained are as follows:1)PVDF polymer cylindrical block was prepared by hot pressing process,and the crystal form of PVDF and P(VDF-TrFE)block body was characterized by XRD and DSC.The results show that the PVDF block has three diffraction peaks in the range of 16-24°,there are mixed crystal forms of?,?and ?,while P(VDF-TrFE)only shows typical diffraction peaks of ? crystal form at 20.7°.The phase transition temperature of P(VDF-TrFE)is 70?-40?,the melting temperature of PVDF with a molecular weight of 90 M is 165.1?,and the melting temperature of P(VDF-TrFE)is 155?.The above parameters provide a basis for selecting the preparation parameters of hot pressing at 165?,2 h,3 MPa,and found that the polymer matrix obtained under this condition is dense,good light transmittance,uniform interface,and excellent mechanical properties,which laid a good foundation for subsequent compounding.2)PMN-PT/PVDF,PMN-PT/P(VDF-TrFE)1-3 piezoelectric composite sheets with 7-hole and 12-hole structures were prepared and polarized in different directions(PMN-PT:1MV/m,5 min;PVDF:5MV/m,110?,30 min).When the composite material is lower than the coercive electric field by 0.5MV/m,only a single-phase inverse piezoelectric effect is generated.Above the coercive field,a "butterfly" strain curve produced by both the polymer and the single crystal is produced.In the low-frequency region,as the frequency increases,the ?r of the composite decreases slowly,and the tan? is relatively stable.In the high-frequency region(>1 MHz),?r decreases rapidly with the increase of frequency.When the aspect ratio G is 1.4,the sample thickness is 2.1 mm,the of the 7-hole composite material is-1501 pC/N,and the kt value is 0.49;the d33 of the 12-hole composite material is 1125 pC/N,and the kt value is 0.97,the composite material Shear stress is generated at the interface between the two phases,and the stress and strain are reversed,resulting in a decrease in piezoelectric constant.When the electric field is 1.85 MV/m,the residual polarization Pr is 6.6 ?C/m2,and the maximum polarization intensity Pm is 7.6?C/m2.The electrical performance is the best under this structural parameter.The above results show that replacing the epoxy-based filler with PVDF polymer with piezoelectric effect can exert the electro-deformation effect of piezoelectric polymer and enhance the piezoelectric effect of inorganic single crystal;in addition,1-3 composite materials It can provide multiple signal receiving points and has potential application prospects in matrix ultrasound probes.