Negative permittivity derived from inductive characteristic in the percolating Cu/EP metacomposites
Negative permittivity derived from inductive characteristic in the percolating Cu/EP metacomposites
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渗流 Cu/EP 复合材料中的感应特性衍生的负介电常数
DOI：
10.1016/j.jmst.2019.07.015
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发表时间：
2019
影响因子：
10.9
通讯作者：
Choy Kwang Leong
中科院分区：
文献类型：
--
作者：
Sun Kai;Xin Jiahao;Li Yaping;Wang Zhongyang;Hou Qing;Li Xiaofeng;Wu Xinfeng;Fan Runhua;Choy Kwang Leong
近年来，随着由周期阵列结构组成的新型超材料的发展，负介电常数受到越来越多的关注。然而，考虑到制备的简便性，重要的是基于材料的本征性质而不是其人为的周期性结构来实现负介电常数行为。本文提出用聚合法制备铜分散在环氧树脂中的渗流复合材料，以实现负介电常数行为。当复合材料中的铜含量达到80 wt%时，电导率突然上升了三个数量级，表现为渗流行为。在渗流阈值以下，电导谱符合Jonscher幂定律；当达到渗流状态时，由于集肤效应，在高频段的电导率逐渐降低。结果表明，其导电机制由跳跃导电转变为电子导电。此外，由于漏电流的存在，在渗流阈值附近，介电常数并不随铜含量的增加而单调增加。同时，在渗流阈值以上观察到符合Drude模型的负介电常数。进一步的研究表明，介电常数与电抗之间存在本构关系。当导电填料略高于渗流阈值时，导电渗流网络的电感特性导致介电常数为负值。这种负电性材料有可能应用于新型电子器件，如高功率微波滤波器、叠层电容器、负电容场效应晶体管和无线圈谐振器等。此外，基于渗流复合材料的设计策略为负电材料的研究提供了一种途径。
Recently, increasing attention has been concentrated on negative permittivity with the development of the emerging metamaterials composed of periodic array structures. However, taking facile preparation into consideration, it is important to achieve negative permittivity behavior based on materials’ intrinsic properties rather than their artificially periodic structures. In this paper, we proposed to fabricate the percolating composites with copper dispersed in epoxy (EP) resin by a polymerization method to realize the negative permittivity behavior. When Cu content in the composites reached to 80 wt%, the conductivity abruptly went up by three orders of magnitudes, suggesting a percolation behavior. Below the percolation threshold, the conductivity spectra conform to Jonscher’s power law; when the Cu/EP composites reached to percolating state, the conductivity gradually reduced in high frequency region due to the skin effect. It is indicated that the conductive mechanism changed from hopping conduction to electron conduction. In addition, the permittivity did not increase monotonously with the increase of Cu content in the vicinity of percolation threshold, due to the presence of leakage current. Meanwhile, the negative permittivity conforming to Drude model was observed above the percolation threshold. Further investigation revealed that there was a constitutive relationship between the permittivity and the reactance. When conductive fillers are slightly above the percolation threshold, the inductive characteristic derived from conductive percolating network leads to the negative permittivity. Such epsilon-negative materials can potentially be applied in novel electrical devices, such as high-power microwave filters, stacked capacitors, negative capacitance field effect transistors and coil-free resonators. In addition, the design strategy based on percolating composites provides an approach to epsilon-negative materials.