BiFeO3基材料的结构调控对多铁性能的影响

BiFeO3 appears to have important potential application because it is known to be the material which is both ferroelectric and ferromagnetic at room temperature. Although the problem of leakage current density and the remnant polarization of the BiFeO3 are improved, its ferromagnetic and ferroelectric are still relatively poor and the magnetoelectric coupling effect is also relatively weak, which limit its practical application. This project intends to use solid-state sintering and hydrothermal method to prepare a variety of microscopic scale Bi1-xAxFe1-yByO3 (A = La, Yb, B = Mn, Te, Nb) polycrystalline samples. The crystal structure and magnetic structure of the samples are determined by X-ray powder diffraction and neutron powder diffraction, so as to get the relationship between multiferroic properties and crystal structures. Meanwhile, the effect of grain size on the material properties is also discussed. The project will use a variety of valence elements doping to find out the key structural parameters that determine the material properties, to explore the magnetoelectric coupling mechanism and its impact on the multiferroic performance mechanism. The obtained structure-property relationship law will be used to guide the synthesis of materials and prepare new materials with superior properties, laying a theoretical and technical foundation for the application of the BiFeO3 based multiferroic materials.

BiFeO3作为少数室温下同时具有铁电性和铁磁性的多铁材料，有重要的理论研究意义和应用价值。虽然其剩余极化强度低和漏导电流大的问题有所改善，但是铁电性能以及铁磁性能仍相对较差，磁电耦合效应也相对较弱，这些都限制了其实际的应用。本项目拟利用固相烧结以及水热法制备多种微观尺度的Bi1-xAxFe1-yByO3（A=La，Yb，B= Mn，Te，Nb）多晶材料。通过X射线衍射、中子衍射确定材料的晶体结构、磁结构，建立起晶体（磁）结构-多铁性能关系规律，并讨论不同晶粒尺寸对材料性能的影响。利用多种价态元素掺杂，找出决定材料性能的关键结构参数，探讨其对多铁性能的影响机制，深入探索磁电耦合机理。将获得的结构-性能关系规律用于指导材料的合成，制备出性能优越的新材料，为此类材料的应用奠定理论和技术基础。

多铁材料具有丰富的物理内涵以及在传感器、调制器、存储以及开关等方面极具应用前景。铁酸铋作为少数室温下同时具有铁电性和铁磁性的多铁材料，是近年来研究的热点。针对目前存在的剩余极化强度低、漏导电流大以及铁磁性弱等问题，本项目以铁酸铋为研究对象采用逐层深入的掺杂策略，从单纯的B位掺杂到与钛酸钡固溶，以及形成固溶体后进一步在A/B位采用阳离子共掺杂等方法解决现存问题。针对铁酸铋合成难、易形成杂相的特点，我们采用了固相烧结、微波烧结以及溶胶凝胶等方法合成了多种BiFeO3基陶瓷材料。研究发现，B位Zr4+高价离子微量掺杂实现了晶体结构、微观形貌的调控，从而引起了本征极化、磁性的提升。与具有优良电性能的钛酸钡固溶后，形成准同型相界。在相转变处，材料的铁磁性以及铁电性稳步提升。同时，协同变化的铁磁、铁电性能预示磁电耦合效应存在。固溶后，采用稀土元素进行A位掺杂，利用磁性元素Gd提升体系的饱和磁化强度到1.08emu/g，同时提升材料的剩余极化强度。通过掺杂含量的变化，实现了介电弛豫以及居里温度的调控。利用镧系4f末位元素Tm掺杂,实现了同种元素A、B位同时掺杂，达到了铁电性、铁磁性同时改善的效果，阐明了离子掺杂对材料结构和多铁性能的影响极其机制，为后续该体系组分设计提供了理论依据和实验基础。