On the possibility of piezoelectric nanocomposites without using piezoelectric materials
On the possibility of piezoelectric nanocomposites without using piezoelectric materials
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DOI：
10.1016/j.jmps.2007.03.016
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发表时间：
2007-11
影响因子：
5.3
通讯作者：
N. Sharma;R. Maranganti;P. Sharma
中科院分区：
文献类型：
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作者：
N. Sharma;R. Maranganti;P. Sharma
在这项工作中，预测的纳米尺寸效应，我们探讨了诱人的可能性，创造明显的压电复合材料，而不使用压电组成材料。在压电材料中，施加的均匀应变可以引起电极化（反之亦然）。晶体学的考虑限制了这一技术上重要的性质，非中心对称系统。即使在非压电材料中，非均匀应变也会破坏材料的反演对称性，从而诱发极化。关键的概念是，所有的压电材料（包括非压电材料）都表现出上述的应变梯度和极化之间的耦合，这是一种实验验证的现象，在某些圈子里被称为挠曲电效应。然而，这种挠曲电耦合通常非常小，除非存在非常大的应变梯度（或相反的极化梯度），否则无法通过实验检测。基于场理论框架和相关的格林函数解决方案在以前的工作中开发，我们定量地证明了“设计压电性”的可能性，即我们利用大应变梯度存在于内部的复合材料包含纳米级的不均匀性，以实现整体非零极化，即使在均匀施加的应力。我们证明了只有当非均匀性的形状和分布都是非中心对称时，上述效应才可能实现。基于有限的材料数据和对不均匀形状和分布的限制性假设，我们的未优化定量结果表明，对于4nm范围内的不均匀尺寸，可以实现接近石英10%的表观压电行为。在未来的工作中，期望基于形状、拓扑结构和适当材料选择的优化来增强性能是不合理的。
In this work, predicated on nanoscale size-effects, we explore the tantalizing possibility of creating apparently piezoelectric composites without using piezoelectric constituent materials. In a piezoelectric material an applied uniform strain can induce an electric polarization (or vice-versa). Crystallographic considerations restrict this technologically important property to non-centrosymmetric systems. Non-uniform strain can break the inversion symmetry and induce polarization even in non-piezoelectric dielectrics. The key concept is that all dielectrics (including non-piezoelectric ones) exhibit the aforementioned coupling between strain gradient and polarization—an experimentally verified phenomenon known in some circles as the flexoelectric effect. This flexoelectric coupling, however, is generally very small and evades experimental detection unless very large strain gradients (or conversely polarization gradients) are present. Based on a field theoretic framework and the associated Greens function solutions developed in prior work, we quantitatively demonstrate the possibility of “designing piezoelectricity,” i.e. we exploit the large strain gradients present in the interior of composites containing nanoscale inhomogeneities to achieve an overall non-zero polarization even under an uniformly applied stress. We prove that the aforementioned effect may be realized only if both the shapes and distributions of the inhomogeneities are non-centrosymmetric. Our un-optimized quantitative results, based on limited material data and restrictive assumptions on inhomogeneity shape and distribution, indicate that apparent piezoelectric behavior close to 10% of Quartz may be achievable for inhomogeneity sizes in the 4nm range. In future works, it is not unreasonable to expect enhanced performance based on optimization of shape, topology and appropriate material selection.