Poly(vinylidene) fluoride (PVDF) is a prototypical piezoelectric polymer, which exhibits a strong piezoelectricity after a poling treatment. In this work, we investigate the polarization behaviors of PVDF film under cyclic electric fields by measuring polarized currents. A compensation method is used to distinguish the polarized current from the capacitive and resistive currents. The PVDF samples with a thickness of 20 or 30 μm and an electrode area of 3 × 3 or 4 × 4 mm² are employed, respectively. From the observations, we find that the electrode area does not affect the current density, but a thicker film has a higher residual polarization due to its larger fraction of effective switchable dipoles. The amplitude of the applied field primarily determines the residual polarization. Impressively, an α‐ to β‐phase transformation occurs above 225 MV · m⁻¹ and the polarized current reaches the maximum and becomes converges at 350 MV · m⁻¹. Moreover, a high degree and reproducible residual polarization is obtained through gradually increasing applied field from 50 to 350 MV · m⁻¹, and the relative standard deviation is 3.74% for 20 available samples. Furthermore, a dipole switching model is used to describe the polarization behaviors of PVDF with a form of f(E) = Ae^{−B|E + C|} and the fitting parameters give a further illustration of polarization behaviors in PVDF. POLYM. ENG. SCI., 60:645–656, 2020. © 2020 Society of Plastics Engineers

中文翻译：

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循环电场下聚偏二氟乙烯薄膜的极化研究

聚偏二氟乙烯（PVDF）是一种典型的压电聚合物，经极化处理后具有很强的压电性。在这项工作中，我们通过测量极化电流来研究PVDF膜在循环电场下的极化行为。补偿方法用于区分极化电流与电容性和电阻性电流。PVDF样品的厚度分别为20或30μm，电极面积为3×3或4×4 mm ²。从观察结果中，我们发现电极面积不影响电流密度，但是较厚的膜由于有效可切换偶极子的比例较大而具有较高的残留极化。外加磁场的幅度主要决定残余极化。令人印象深刻的是从α到β的相变发生在225 MV·m ^-1以上，极化电流达到最大值并在350 MV·m ^-1处收敛。此外，通过将施加场从50 MV·m ^-1逐渐增加，可以获得高度且可重现的残留极化，并且对于20个可用样品，相对标准偏差为3.74％。此外，使用偶极子切换模型以f（E）= Ae ^{- B |}的形式描述PVDF的极化行为。^{E  +  C |} 拟合参数进一步说明了PVDF中的极化行为。POLYM。ENG。SCI。，60：645–656，2020.©2020塑料工程师协会