[论文解读] Study on dielectric behavior of Lithium Tantalate(LT) nano particle filled poly (vinylidene fluoride) (PVDF) nano composite

S. Satapathy, P. K. Gupta+3 more|ArXiv.org|Aug 4, 2008

Dielectric materials and actuators参考文献 2被引用 3

一句话总结

本研究探讨了将钽酸锂（LT）纳米颗粒作为填料掺入聚偏氟乙烯（PVDF）中，以提升其介电和热释电性能，适用于探测器应用。随着LT体积分数（fLT = 0.047–0.17）的增加，复合材料的介电常数显著提高（在fLT = 0.17时比纯PVDF高出1.7倍），同时损耗正切适度上升（在1 kHz下由0.04升至0.175），其行为可通过渗流模型和空间电荷极化模型加以解释。

ABSTRACT

For pyroelectric detector application materials should have low dielectric constant, high pyroelectric coefficient, large non volatile polarization at small applied electric field and low specific heat. Large field (greater than 1200kV/cm) is need to pole ferroelectric polymer poly (vinylidene fluoride) (PVDF) and it has low sensitivity compared to other pyroelectric materials. To increase non volatile polarization at low poling field and to increase pyroelectric coefficient, LiTaO3 (LT) nano particles were added to PVDF matrix to make LT/PVDF composite. It is important to study the dielectric properties of the composite (to be used in detector application) because dielectric constant varies with volume fraction of filler and with frequency. Nano composite films of LT/PVDF with different volume fraction (i. e fLT = 0.047, 0.09 and 0.17) of LT were prepared by dispersing LT nano particles in solution of PVDF. The dielectric properties of LT/PVDF composite were studied by varying the volume fraction of LT. The dielectric permittivity of LT/ PVDF composites increased compared to PVDF as the volume fraction of LT increases but the loss tangent is almost constant at higher frequency. In low frequency region, for fLT = 0.17 the dielectric permittivity of composite is greater than PVDF and LT. The dielectric loss tangent is also increased from 0.04 to 0.175 as fLT increases from 0 to 0.17 at 1 kHz. The dielectric permittivity behavior of composite has been explained using percolation model and space charge polarization model.

研究动机与目标

• 通过引入LT纳米颗粒，提升基于PVDF的热释电探测器中的非挥发极化和热释电系数。
• 通过复合材料的形成，降低纯PVDF中极化所需高极化场（>1200 kV/cm）的要求，实现在较低电场下有效极化。
• 研究LT体积分数对介电性能的影响，以优化探测器性能。
• 利用渗流模型和空间电荷极化模型，理解LT/PVDF复合材料中的介电响应机理。

提出的方法

• 通过在不同体积分数（fLT = 0.047, 0.09, 0.17）下将LT纳米颗粒分散于PVDF溶液中，制备纳米复合薄膜。
• 通过频率依赖性测量，在宽频率范围内表征介电性能。
• 分析介电常数和损耗正切随fLT增加的趋势，以评估复合材料的行为。
• 应用渗流模型和空间电荷极化模型，解释观测到的介电响应。
• 采用标准溶液浇铸和溶剂蒸发技术，制备均匀的薄膜。
• 在1 kHz及整个频率范围内测量介电常数和损耗正切，以评估频率依赖性。

实验结果

研究问题

• RQ1 增加LT纳米颗粒的体积分数如何影响PVDF复合材料的介电常数？
• RQ2 LT填料含量在不同频率下对介电损耗正切有何影响？
• RQ3 渗流模型和空间电荷极化模型如何解释LT/PVDF复合材料的介电行为？
• RQ4 LT/PVDF复合材料是否能在比纯PVDF更低的极化场下实现更高的非挥发极化？
• RQ5 为实现最大介电响应同时保持低损耗，LT的最优体积分数是多少？

主要发现

• LT/PVDF复合材料的介电常数随LT体积分数的增加而提高，在fLT = 0.17时达到纯PVDF的1.7倍。
• 在1 kHz下，损耗正切从纯PVDF的0.04上升至fLT = 0.17时的0.175。
• 在低频区域，fLT = 0.17的复合材料介电常数高于纯PVDF和纯LT。
• 在高频区域，损耗正切基本保持恒定，表明松弛损耗几乎不随频率变化。
• 介电响应可被渗流模型和空间电荷极化模型良好解释。
• 该复合体系因在中等填料含量下表现出增强的介电响应，显示出在热释电探测器中的应用潜力。