热处理方式对P(VDF-co-TrFE)压电、介电及铁电性能的影响

Influence of Thermal Processing on Piezoelectric,Dielectric and Ferroelectric Properties of a Poly(vinylidenefluoride-co-trifluoroethylene) Copolymers

采用溶液流延法制备了铁电聚合物聚偏氟乙烯-三氟乙烯(P(VDF-co-TrFE))厚膜,用X射线衍射仪(XRD)和热重分析仪(DSC)确定了聚合物晶型,并用偏光显微镜(POM)比较了不同热处理后聚合物的结晶形态。在此基础上,用热极化方式处理了P(VDF-co-TrFE),使该材料的压电系数(d33)提高到-22 pC/N,并比较了不同极化电场下三种热处理聚合物的压电性能。然后用介电测试系统表征了退火处理后不同d33P(VDF-co-TrFE)样品的介电性能,结果表明高压电性会降低此类材料的介电常数。最后通过铁电测试系统解释了P(VDF-co-TrFE)偶极子转向对材料极化强度的影响,阐明了其压电性的来源和影响机理。研究结果表明,通过物理方式改善聚合物的结晶性能,可提高材料剩余极化强度,并可获得高压电性能聚合物厚膜。

Poly（vinylidenefluoride-co-trifluoroethylene）（P（VDF-co-TrFE）） ferroelectric thick films are prepared in solution casting method.X-Ray Diffraction（XRD） and Differential Scanning Calorimeter（DSC） are employed to character the crystal structures of the ferroelectric copolymer.On the basis of which Polarized Optical Microscopy（POM） is used to treat the copolymer so as to make the piezoelectric constant（d33） raise to-22 pC/N and to compare the crystal properties of the copolymer with different thermal treatments of three kinds.Then P（VDF-co-TrFE） electrets are obtained by hot-poling process and the dielectric properties of annealed P（VDF-co-TrFE） with different d33 are compared through the dielectric test system.The results illustrate that dielectric constants（εr） decrease as the function of d33 increase.Finally,ferroelectric test system is employed to express how dipoles reverse influence on polarization properties.The results illustrate that the improvement of crystal properties as well as remnant polarization are an effective way to obtain copolymer films with high piezoelectric property.