核/壳结构磁电复合材料的设计与耦合机理研究

Multiferroic materials with coexistence of ferroelectricity and ferromagnetism have recently attracted increasing interest because of their significant technological promise in novel multifunctional devices. In this program, to obtain high magnetoelectric properties, the core/shell structure is designed as basic micro building blocks to construct multiferroic composite materials. A general approach of combined hydrothermal and annealing process is proposed for the fabrication of ferrite/perovskite oxide core/shell nanostructures with uniform size and shape. The structure of the interface and the interaction of the core and shell materials will be investigated and novel properties of the special structure will be explored. With the help of some in situ synthesis technology, many ordered composite materials with remained core/shell feature will be fabricated. The mechanism of magnetoelectric effect will be investigated by micro and macro magnitude respectively and the results of this program will extend the understanding between these small functional units and the material properties. New application areas will be explored based on the properties of the materials which will promote the practical progress of multiferroic materials.

多铁性材料由于兼具铁电性与铁磁性，并且不同的铁性间可相互耦合产生新性能，为发展新型器件模型提供了广阔的应用前景，已成为近来国际上一个新的研究热点。本项目以多铁性磁电复合材料的结构设计为主要研究方向，通过实验设计引入铁氧体/钙钛矿结构氧化物core/shell 复合结构作为材料微观结构单元。以典型的铁氧体、钙钛矿结构铁电体为材料体系，探索实现铁电体作为包覆壳层的包覆方法，得到理想的core/shell纳米磁电复合颗粒；研究复合颗粒的界面结构以及包覆结构对于核心和壳层材料的影响，开发包覆后复合颗粒的独特性能；以包覆颗粒作为基本组成单元，构筑有序的厚膜和块体磁电复合材料；从微观和宏观上研究两相的磁电耦合机理，探索材料微观功能单元与宏观性能间的关系；在获得良好磁电性能的前提下，开发材料的应用领域，推动多铁性材料的实用化进程。

多铁性材料由于兼具铁电性与铁磁性，并且不同的铁性间可相互耦合产生新性能，为发展新型器件模型提供了广阔的应用前景。本论文以制备多铁性铁氧体/钙钛矿结构铁电氧化物的核/壳(core/shell)纳米结构为主要研究内容，从颗粒制备到块体材料开展了一系列研究。在乙二醇-NaOH体系中利用水热法合成了铁氧体和Co等铁磁性颗粒。通过调节反应物配比，制备了形貌和磁性能可调的磁性颗粒；研究了试剂浓度以及反应温度对钴金属颗粒形貌的影响，分析了物相和微结构的演变过程，进而探索出不同微结构的钴金属颗粒的磁学性能。开展ABO3结构铁电颗粒的制备，通过简单的热溶剂法合成了Er3+掺杂的KNbO3纳米片结构，这种掺杂的钙钛矿结构具有优异的上转换（UC）光致发光（PL）特性。利用水热和热处理结合的方法实现了γ-Fe2O3/PZT，PbFe12O19-PZT等材料的理想包覆，包覆后的两相表现出强的相互作用。同时开展特定结构磁电复合薄膜和块体材料的设计和制备工作。