立方核壳晶粒模型的分布介电效应

Dielectric Effect of Distributed Curie Temperature in a Model of Cubic Core-Shell Grain

摘要: 用立方晶粒模型模拟多面体核壳结构，得到了有效介电常数与核壳尺寸的关系。当壳层为极薄的低介电常数时，该关系表现为晶粒尺寸效应：介电峰移向低温及介电常数下降；当壳层较厚且核与壳介电常数峰不同时，核对介电常数的贡献为其尺寸平方比相关的线性叠加关系。二阶铁电相变时，分布的居里温度会使介电峰向高温移动，同时介电常数减小；分析结果发现：其顺电相介电隔离率的温度关系不能用幂律表示。壳层居里温度的线性分布与核的高斯分布结合能够得到较为平稳的介电常数温度关系。认为铁电体极化强度的平方相当于偶极子的作用，利用偶极子复介电常数关系，导出了分布式铁电相变的损耗温度关系。

Abstract: A model of cubic core-shell grain with the distribution of the Curie temperature is proposed for simulation of the polyhedron core-shell structure to obtain the size related dielectrics. When the shell is a very thin layer with low dielectric constant, the shell has the grain-size effect: dielectric constant decreases and the peak moves to low temperature. When the shell is thick with different dielectric peak from the core one, the contribution of the core to the dielectric constant is a linear relation to the square of it size. The distribution of the Curie temperature will move dielectric peak to high temperature with dropping dielectric constant, and the temperature relation of im-permeability in paraelectric phase can not be expressed by the power-law. Ferroelectrics will have high stability of relation of dielectric constant with temperature for the combination of the shell in linear distribution and the core in Gaussian distribution. It is the square of spontaneous polariza-tion in ferroelectrics that has the same function as dipole in dielectrics for contribution to the complex dielectric constant, and therefore a temperature dependent dielectric loss of the distri-bution of the Curie temperature is derived.