Designing soft pyroelectric and electrocaloric materials using electrets
Designing soft pyroelectric and electrocaloric materials using electrets
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DOI：
10.1039/c8sm02003e
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发表时间：
2019-01-14
期刊：
影响因子：
3.4
通讯作者：
Sharma, Pradeep
中科院分区：
文献类型：
--
作者：
Darbaniyan, Faezeh;Dayal, Kaushik;Sharma, Pradeep
温度的变化可以使热释电材料电极化。在其相反的表现形式中，电热效应导致由于施加电场而引起的温度变化。这些现象有着广泛的应用，从红外探测传感器、固态制冷到能源收集。然而，热释电-电热效应通常是在某些类型的硬脆晶体材料中观察到的，这些材料必须满足严格的晶格对称条件。然而，一些有限的实验表明，在软泡沫中嵌入固定电荷和偶极子(从而产生驻极体状态)可能会导致类似热释电的响应以及软物质所需的大变形。在这项工作中，我们发展了一个关于软驻极体的电、热和机械耦合响应的系统理论。通过简单的例证，我们得到了驻极体热释电系数和电热系数的闭合显式表达式。虽然以前已经注意到驻极体中的热释电，但我们的推导公式为解释(并最终设计)这种效应提供了一个明确的量化基础，并深入了解了几何非线性变形和麦克斯韦应力是如何引起这种效应的。我们提出了获得更大的热释电和电热响应的条件。特别是，首次预测了这种材料的电热效应，结果表明，在10 mV cm(-1)的电场作用下，适当的设计和合理的材料选择可以使温度降低1.5K。
A temperature variation can electrically polarize a pyroelectric material. In its converse manifestation, the electrocaloric effect entails a change in temperature due to the application of an electric field. These phenomena have wide applications ranging from infrared detection sensors and solid-state refrigeration to energy harvesting. However, the pyroelectric-electrocaloric effect is typically observed in certain classes of hard, brittle crystalline materials that must satisfy a stringent set of lattice symmetry conditions. Some limited experiments have however demonstrated that embedding immobile charges and dipoles in soft foams (thus creating an electret state) may lead to a pyroelectric-like response as well as large deformations desired from soft matter. In this work, we develop a systematic theory for coupled electrical, thermal and mechanical responses of soft electrets. Using simple illustrative examples, we derive closed-form explicit expressions for the pyroelectric and electrocaloric coefficients of electrets. While pyroelectricity in electrets has been noted before, our derived expressions provide a clear quantitative basis to interpret (and eventually design) this effect as well as insights into how the geometrically nonlinear deformation and Maxwell stress give rise to its emergence. We present conditions to obtain a larger pyroelectric and electrocaloric response. In particular, the electrocaloric effect is predicted for the first time in such materials and we show that a proper design and a reasonable choice of materials can lead to a temperature reduction of as much as 1.5 K under the application of electrical fields of 10 MV cm(-1).