An internal-variable-based interface model for the charging process of ferroelectrets
An internal-variable-based interface model for the charging process of ferroelectrets
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DOI：
10.1016/j.euromechsol.2013.12.011
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发表时间：
2014-11
影响因子：
4.1
通讯作者：
Bai-Xiang Xu;H. Seggern;S. Zhukov;D. Gross
中科院分区：
文献类型：
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作者：
Bai-Xiang Xu;H. Seggern;S. Zhukov;D. Gross
带电的微孔泡沫，称为铁驻极体，表现出非常大的纵向压电系数。在目前的构型中，微孔材料被夹在两个固体材料之间，可以阻止电荷的运动。在铁电驻极体的充电过程中，泡沫的气孔中发生了电击穿(帕森击穿)，并引入了自由电荷对。这些对被外加电压感应的电场隔开。根据极性的不同，它们被重新定位在聚合物和电击穿介质之间的界面上，在那里它们被准静态地捕获。界面电荷是观察到的铁驻极体的压电性的关键。本文提出了一种基于内变量的界面模型来模拟铁电驻极体的充放电过程。该模型还考虑了界面电荷之间的静电力。对于块体行为，采用了基于麦克斯韦应力的机电模型。特别阐述了模型的二维非线性有限元实现，其中包括一种新型的嵌入界面单元。对夹层铁电驻极体的模拟表明，界面模型可以再现界面电荷密度的滞后行为，并与相应的实验结果进行了比较。利用该模型进一步数值研究了几何参数、弹性参数和电学参数对磁滞回线和压电系数的影响。该模型还被用来模拟透镜形状的铁驻极体单元。
Electrically charged micro-porous foams, referred to as ferroelectrets, exhibit a very large longitudinal piezoelectric coefficient. In the present configuration the microporous material is sandwiched between two solid materials which can block the motion of charges. During the charging process of the ferroelectret electrical breakdown (Paschen breakdown) takes place in the air pores of the foam and introduce free charge pairs. These pairs are separated by the electric field induced by the applied voltage. Depending on the polarity they are relocated at the interfaces between the polymer and the electrically broken-down medium, where they are trapped quasistatically. Charging of the interfaces is key for the observed piezoelectricity of ferroelectrets. In the present article, an internal-variable-based interface model is proposed to simulate the charging and discharging of ferroelectrets. The model includes also the electrostatic force between the interface charges. For the bulk behavior, an electromechanical model based on the Maxwell stress is used. In particular, a 2D nonlinear finite element implementation of the models is elaborated, which involves a novel embedded interface element. Simulations of a sandwiched ferroelectret show that the interface model can reproduce the hysteresis behavior of the interface charge density, as it is demonstrated by the comparison with the corresponding experimental results. The model is further used to numerically study the influences of geometric, elastic and electrical parameters on the hysteresis and the piezoelectric coefficients. The models are also used to simulate a lens-shaped ferroelectret unit.