铁酸铋材料的相界调控、相组成优化及其与电学性能的关联研究

Multiferroics are key materials with potential important applications, and the related research is one of the international forefronts and hot topics in the field of materials science and engineering. Choosing the bismuth ferrite material system,the related researches will be conducted against two key scientific questions, which are assigned to "Phase boundary modification, phase compositions optimization, and phase transition mechanism of bismuth ferrite materials" and "Interrelationship between phase transition characteristics and enhanced electrical properties of bismuth ferrite materials". The core idea of this project is to modify the phase boundary by using the integrated use of a variety of measurements, to optimize the phase compositions, to realize the enhancement of electrical properties, and to explain the underlying physical mechanisms of bismuth ferrite materials.The research contents are listed as followed: Modifying the phase boundary of bismuth ferrite ceramics and thin films by several methods; Investigating the regulation of phase boundary modification and physical mechanisms of phase transition of bismuth ferrite materials; Illuminating the interrelationship between phase compositions and electrical properties of bismuth ferrite materials; Mastering the regulation of phase boundary modification, phase compostions optimization, and enhanced electrical properties of bismuth ferrite materials,and illuminating the physical mechanisms of its enhanced electrical properties. This project is both important and urgent, expected to achieve an important breakthrough in the basic researches of bismuth ferrite materials; more than fifteen papers cited by SCI will be published; over two invention patents will be authorized or applied; more than eight MSc and PhD candidates will be cultivated; keeping the related research achievement of bismuth ferrite materials in our country at the international forefront, having an important significance for the development of ferroelectrics and piezoelectrics.

多铁材料是具潜在重要应用的关键功能材料，相关研究一直是材料科学与工程的国际前沿和热点之一。本项目选择铁酸铋材料体系，针对"铁酸铋的相界调控、相组成优化与相变机理"、"铁酸铋的相变特性及其与电学性能增强的内在关联"两个关键科学问题开展研究。本项目的核心思想是综合运用多种措施调控铁酸铋材料的相界，优化其相组成，实现其电学性能增强。主要研究内容包括：采用多种调控措施开展铁酸铋陶瓷和薄膜的相界调控；研究铁酸铋材料的相界调控规律和相变物理机制；阐明铁酸铋材料的相组成与电学性能的关联；掌握铁酸铋材料的相界调控、相组成优化与电学性能增强的规律，阐明其电学性能增强的物理机理。本项目重要且紧迫，以期在铁酸铋材料体系基础研究中有重要突破；发表高水平SCI收录论文15余篇；授权（或申请）发明专利2项以上；培养博硕士研究生8余人；使我国铁酸铋材料的相关研究成果继续处于国际前沿，并对我国铁电压电学发展具重要意义。

铁酸铋材料因其性能可调且具丰富物理内涵，成为当前国际材料研究的前沿和热点之一。本项目选择铁酸铋材料为研究对象，研究并阐明了相界调控、相组成优化与电学性能之间的关联，提升电学性能并探讨其相关物理机理。本项目重点研究了三个关键科学问题并取得具有显示度的研究成果：组分设计与相界调控的关联、相界中的相组成优化与电学性能的关联、电学性能增强的物理机理。通过四年的努力，取得的主要成果如下：.(1) 采用组分设计与优化，在铁酸铋材料中实现了性能提升。采用淬火烧结工艺制备了铁酸铋陶瓷，并在宽的烧结温度范围内实现了良好的压电和介电性能。例如：La、Sm、Sc等元素取代铁酸铋陶瓷Bi或Fe位，实现了增强的压电性能(d33=50 pC/N)和铁电性能(2Pr=50~60 μC/cm2)以及非常低的介电损耗。在La和Co改性的铁酸铋薄膜中实现了好的介电性能、提升的铁电性能(2Pr~175.6 μC/cm2)以及好的铁电疲劳特性。.(2) 通过相界构建以及相组成优化增强了铁酸铋陶瓷的压电、铁电及应变性能。在铁酸铋陶瓷中，通过引入BaTiO3可实现多相共存并提升压电系数(d33=180 pC/N)。此外，调控离子取代的铁酸铋陶瓷中的缺陷，获得了较高的应变值（~0.66%）并发现应变记忆效应。最后利用Bi(Mg,Nb)O3改性BFO-BTO陶瓷并诱导弛豫铁电体的形成，实现了单轴/双轴应变值随温度的快速提升。当测试温度为200 oC、驱动电场E=4 kV/mm时，单轴应变值达到了0.32%，d33*为800 pm/V, H=5%。.(3) 阐述了铁酸铋陶瓷电学性能增强的物理机理以及相组成优化与性能的关联。离子取代的铁酸铋陶瓷材料体系压电性能与漏电流、微观结构、杂相以及Fe变价息息相关。而BFO-BTO基陶瓷压电性能的贡献主要来源于多相共存。此外，铁酸铋陶瓷内部的缺陷偶极子直接影响其铁电和应变特性。而弛豫相结构的设计也是获取高应变的有效措施。.本项目研究期间，作为第一作者或者(共同)通讯作者发表SCI收录论文17篇，包括Prog Mater Sci (2篇), J Mater Chem C（4篇）等, 一篇论文入选ESI高被引论文；1人获准国家自然科学优秀青年基金，正在培养博士后1名、博士4人以及硕士4人。受Springer Nature出版社邀请，独著撰写一本英文专著。完成了本项目的任务。