应变梯度对铁电材料力电耦合性能的调控

项目名称： 应变梯度对铁电材料力电耦合性能的调控

项目编号： No.11472242

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 数理科学和化学

项目作者： 王杰

作者单位： 浙江大学

项目金额： 90万元

中文摘要： 本项目将基于铁电材料Landau-Devonshire非线性热力学理论，考虑材料中应变梯度和电极化的耦合，提出能够同时包含挠曲电效应和表面效应的新型相场模型。结合第一性原理计算和新型相场模型，建立微纳米尺度下铁电材料分层次的多尺度理论模型。采用多尺度的理论模型预测应变梯度、表面效应和晶体缺陷对铁电材料表观压电系数、介电常数和弹性常数的调控作用。研究应变梯度和晶体缺陷对铁电材料中新畴形核与长大以及畴壁运动的影响。探讨挠曲电效应和表面效应与材料微观畴结构及宏观性能之间的内在关联。基于挠曲电效应、表面效应以及晶体缺陷调控的基本原理，针对含有不同晶体缺陷的微纳米铁电材料，设计相应的表面边界条件和应变梯度模式，优化畴结构的空间分布，以提高材料力学、电学及多场耦合性能。

中文关键词： 应变梯度；铁电材料；相场法；第一性原理；多场耦合

英文摘要： In this project, a new phase field model will be proposed for ferroelectric materials based on the Landau-Devonshire nonlinear thermodynamics theory. The phase field model includes the coupling between the strain gradients and polarization, which can describe the flexoelectricity and surface effect of ferroelectric materials. A hierarchical multiscale model will be developed for micro- and nano-scale ferroelectric materials by combining the first-principles calculation and the proposed phase field model. The multiscale model will be employed to investigate the effect of strain gradients,surface and defects on the apparent piezoelectric coefficients, dielectric constants and elastic constants. The influence of strain gradients and defects on the nucleation and growth of new domain and the motion of domain wall will be studied. The intrinsic relations between the flexoelectricity, surface effect, microscopic domains and macroscopic material properties will be examined. Based on the tuning principles of flexoelectricity, surface effect and defects, different boundary conditions of surface and different models of strain gradient will be devised to optimize the domain structures for the micro and nano ferroelectric materials with different geometries, which will eventually enhance the mechanical, electrical and multi-field coupling properties of the materials.

英文关键词： Strain gradient;Ferroelectric materials;Phase field method;First- principles calculations;Multi-field coupling