铁电纳米颗粒相变中的尺寸效应

由铁电纳米颗粒和介电质基体组成的复合材料具有很多功能特性,这些特性可广泛用于新型电子和能量收集装置.然而,铁电颗粒的形状、尺寸和在介电质基体中的取向对这些功能的影响还没有被研究清楚.利用一种中尺度建模方法,模拟了具有极性、弹性和热自由度的铁电纳米复合材料的性质,以及这些性质对尺寸、形状和取向的依赖性.基于时间依赖的朗道...

Study on size effect in ferroelectric nanoparticles phase transition

Composite materials comprised of ferroelectric nanoparticles in a dielectric matrix have a variety of functional properties attractive for a wide range of novel electronic and energy harvesting devices. However, the dependence of these functionalities on shapes, sizes and orientation of ferroelectric particles is currently not fully understood. In this paper, a mesoscale modeling approach is developed to simulate the properties of ferroelectric nanocomposites with polar, elastic, and thermal degrees of freedom, as well as the dependence of these properties on the size, shape, and orientation. A time-dependent Ginzburg-Landau approach combined with coupled physics finite element method was used to simulate the behavior of polarization in isolated PbTiO3 or BaTiO3 nanoparticles embedded in a dielectric medium. The equilibrium polarization is strongly affected by particle size, as well as the choice of inclusion and matrix materials, with monodomain, vortex-like and multidomain patterns emerging for various combinations of size and materials parameters. The calculations result show that there is a critical particle size below which ferroelectricity vanishes. For the PbTiO3 and BaTiO3 particle, this size is 2 and 3.4 nm, respectively.