应变条件下四方铁电体中90度铁电畴壁结构演化的像差校正电子显微学研究

项目名称： 应变条件下四方铁电体中90度铁电畴壁结构演化的像差校正电子显微学研究

项目编号： No.51501194

项目类型： 青年科学基金项目

立项/批准年度： 2016

项目学科： 一般工业技术

项目作者： 唐云龙

作者单位： 中国科学院金属研究所

项目金额： 20万元

中文摘要： 铁电畴壁及其外场动力学特性决定了铁电材料的使役行为，但PbTiO3等四方铁电体中90度畴壁结构及其物理特性的研究历来具有分歧；研究90度铁电畴壁的原子结构、应变宽度及其对局域弹性应变的响应等物理参量对理解和调控铁电材料的极化及压电性能至关重要。本项目拟利用衬底应变调控系列PbTiO3薄膜中90度铁电畴的结构组态；结合像差校正电子显微技术与第一原理计算，在原子尺度揭示90度畴壁的精细结构及其随局域应变的演化规律。拟通过精确测定像差校正条件下高分辨像中Pb、Ti等离子坐标，准确提取不同应变状态下90度畴壁及其附近晶格的应变分布与极化离子位移信息，结合第一原理模拟，定量描述90度畴壁的畴壁能与运动势垒、应变宽度和极化特征与局域弹性应变之间的关系及其演化特征。项目的完成不但有助于系统性认识四方铁电体中90度铁电畴壁的原子结构特征，而且为深入理解铁电畴壁的使役行为提供重要的原子尺度结构信息。

中文关键词： 铁电畴壁；；原子结构；高分辨电子显微学；应变；结构演化

英文摘要： The properties of ferroelectric materials are determined by field-dependent domain wall dynamics. However, the structures and properties of 90 degree domain walls in tetragonal ferroelectrics, like PbTiO3, are still unclear. Revealing the atomic structures, strain widths and their response to local strains is essential to understanding/modulating polar and piezoelectric properties of ferroelectric materials. In this project, we will investigate the fine structures of 90 degree domain walls at the atomic scale as well as their evolutions under strains by using a combination of aberration-corrected transmission electron microscopy and first-principles calculations. The configurations of 90 degree domain walls are controlled in PbTiO3 films prepared under series of strains by PLD technique. The strains and polar ion displacements of domain walls and nearby unit-cells will be precisely determined through measuring the positions of Pb, Ti columns in images under aberration-correction condition. Combined with first-principles calculations, the domain wall energy, energy barrier for the movement of domain wall, strain widths and polarization distribution as well as their evolutions under location strains will be quantitatively elucidated. The studies in this project would help to systemically understand atomic structures of 90 degree domain walls in tetragonal ferroelectrics, and provide fundamental information for the exploration of numerous novel domain wall phenomena in ferroelectrics.

英文关键词： ferroelectric domain wall;atomic structure;high-resolution TEM;strain;structural evolution