Zhang Jianwei, Du Xiaoping, Zhao Jiguang, Duan Yongsheng
Graduate Schools, Space Engineering University, Beijing 101416, China.
Department of Electron & Optics Engineering, Space Engineering University, Beijing 101416, China.
Nanomaterials (Basel). 2022 Apr 11;12(8):1293. doi: 10.3390/nano12081293.
Understanding the effects of polar nanoregions (PNRs) dynamics on dielectric properties is a complex question of essential importance for both fundamental studies of relaxor ferroelectrics and their applications to electro-optic devices. The frequency dependence of dielectric response to the bias electric field opens a brand new window for the study of this problem. A novel model from mesoscopic to macroscopic, revealing the relationship between the dielectric permittivity to the applied electric field, temperature, and PNRs, was established based on mean field approximation and the theory of continuum percolation, and not only validates the field-induced percolation and the relaxation time divergency at the freezing temperature, but also predicts the frequency dependence of dielectric response. Unexpectedly, the model reveals the field-enhanced correlation length results in the nonmonotonic behavior of dielectric response, and implies that the increased orientation consistency of dipolar clusters and coercive fields originated from inherent inhomogeneity slow down the relaxation time of PNR reorientation. Considering the multi-scale heterogeneity of PNRs in relaxor, we found that the increased heterogeneity degree reduces the dielectric permittivity, but changes the slope of dielectric response to the bias electric field.
理解极性纳米区域（PNRs）动力学对介电性能的影响，对于弛豫铁电体的基础研究及其在电光器件中的应用来说，都是一个极其重要的复杂问题。介电响应随偏置电场的频率依赖性为研究该问题打开了一扇全新的窗口。基于平均场近似和连续渗流理论，建立了一个从中观到宏观的新颖模型，该模型揭示了介电常数与外加电场、温度以及PNRs之间的关系。它不仅验证了场致渗流以及冻结温度下的弛豫时间发散，还预测了介电响应的频率依赖性。出乎意料的是，该模型表明场增强的关联长度导致了介电响应的非单调行为，这意味着偶极团簇取向一致性的增加以及源于固有不均匀性的矫顽场会减缓PNR重新取向的弛豫时间。考虑到弛豫体中PNRs的多尺度不均匀性，我们发现不均匀性程度的增加会降低介电常数，但会改变介电响应随偏置电场的斜率。
