PZT压电陶瓷缺陷偶极子诱导的电致应变效应及相关物理机制研究

Recently, based on symmetry-conforming principle for point defect, the large recoverable electrostrain effect induced by defect dipole have widely been paid attention. However, the microstructure regulation mechanism of high recoverable electrostrain is not clear, and the induced high recoverable electrostrain is uncertain. PZT piezoelectric ceramics close to the morphotropic phase boundary (MPB) have multi-scale domain structures. The interaction between these polarities and their response to external field are much complicated. Based on our earlier research results, we propose an novel idea to control the status of defect dipole and ferroelectric domain by changing the composition, the grain size and the post process method. The influence of composition and process on the electrostrain properties will be studied, and the structure regulation mechanisms of defect dipole and ferroelectric domain will be revealed. The defect dipole and the domain response to external field and their affect on the electrostrain will be investigated. The purpose of this project is to establish the relationship between the macroscopic electrostrain property and microscopic physics mechanism, and to develop the novel way to obtain the large recoverable electrostrain and strain memory effect. This project will promote the understanding about the electrostrain induced by defect dipoles. Moreover, these achievements could provide scientific directions and references for the development of novel devices as potential candidate for future applications.

近年来，基于点缺陷短程有序对称一致性原理、由缺陷偶极子诱导的巨可逆电致应变效应日益受到广泛关注。目前关于压电材料获得高可逆电致应变的微观结构调控机制尚不清晰，大应变获得存在不确定性。准同型相界（MPB）附近PZT压电陶瓷存在多尺度畴结构，引入缺陷偶极子时，材料中极性结构之间相互作用以及对外场响应更加复杂。本项目在前期研究基础上，以MPB附近PZT基压电陶瓷为研究对象，从调控缺陷偶极子和铁电畴状态本质出发，通过改变组成、晶粒尺寸、加载历史，研究不同组成和制备工艺对电致应变特性的影响规律；揭示缺陷偶极子与多尺度铁电畴结构调控机制; 研究外场下缺陷偶极子和铁电畴响应行为以及对电致应变特性的影响，建立宏观电致应变与微观结构的内在联系，发展出获得高电致应变和稳定应变记忆效应的新方法。本项目的实施将深化对与缺陷偶极子相关的电致应变效应的理解，为设计高性能新材料、拓展压电材料新应用提供科学依据和指导。

缺陷偶极子与铁电畴的相互作用可以诱导高电致应变效应，但目前对于这一效应的研究大多基于宏观电学性能测试分析，获得高电致应变的微观结构调控机制尚不清晰，大应变获得存在不确定性。项目组以MPB附近PZT基压电陶瓷为研究对象，从调控缺陷偶极子和铁电畴结构出发，改变材料组成、加载历史，研究了不同组成和外场条件下PZT压电陶瓷应变、应变记忆效应、电致疲劳特性及铁电畴动力学行为，揭示缺陷偶极子和铁电畴结构调控应变及应变记忆效应机制；在此基础上，基于协同调控缺陷偶极子及畴结构方法获得了大应变BaTiO3基压电陶瓷，证实了该高电致应变调控新方法的普适性。. 重要结果：（1）提出了一种协同调控缺陷偶极子与铁电畴状态提高压电材料应变和抗疲劳特性的新方法，获得了等效d33*高达1530pm/V的PZT压电新材料（2）设计出一种“畴夹持结构”，利用铁电畴和缺陷偶极子相互作用，Mn掺杂BaTiO3在5kV/mm电场下单极电致应变可达0.23%，应变提升近50%（3）通过引入引入A空位晶格缺陷材料，BiFeO3-BaTiO3电致应变达到0.45%,同时兼具低滞后（29%）及高温度稳定性（25℃-100℃应变变化率小于10%）（4）通过施加倍半极电场，在老化和极化处理的PZT样品中获得了高达0.3%应变记忆效应。. 本项目的实施可促进对缺陷偶极子与铁电畴相互作用机理的认识，深刻理解MPB附近压电陶瓷的结构-性能本质关联，相关物理机制可以拓展到多铁（铁磁、磁电耦合）材料中，为设计高性能新材料、拓展压电材料新应用和开发新型智能器件提供科学依据和指导。