多铁性锰氧化物的制备、结构表征及物性测试

论文总字数：17841字

摘 要

BiFeO₃作为为数不多的室温下同时存在铁电性和反铁磁性的单相多铁材料，在物理学、材料科学和信息存储技术方面备受关注。然而，BiFeO₃的铁磁性和铁电性分别由不同的离子提供，这就造成满足铁电性和铁磁序的结构特征（特别是对铁离子的电子排布的要求）相互排斥，虽然各种制备BiFeO₃的方法已经逐步完善，但室温下磁性较弱的问题没有得到明显改善。因此，在本文中，我们通过对BiFeO₃进行B位离子掺杂，观察其结构性质的变化并与之性能进行对比，研究有效提高BiFeO₃材料磁电耦合性能的方法和措施。

本文以硝酸铋、硝酸铁、硝酸钴为原料，酒石酸作为络合剂，采用溶胶-凝胶法制备出一组纯相的BiFe_1-xCo_xO₃（x=0,0.01,0.03,0.05）粉体样品，用X射线衍射（XRD）观察单相Co掺杂BiFeO₃样品的结构变化，以及分别测量观察BiFe_1-xCo_xO₃（x=0,0.01,0.03,0.05）粉体样品的铁电性和基本磁性。我们观察到，BiFeO₃材料的晶格结构没有因为离子掺杂而发生变化，依然为扭曲的钙钛矿结构。Co³ 离子掺杂使得BiFeO₃材料磁性有所增强，对其铁电性也有所改变，掺杂量x=0.01时铁电性最好。

关键词：多铁材料；BiFeO₃；溶胶-凝胶法；掺杂

MULTIFERROIC PRIPERTIES OF COBALT-DOPED BiFeO₃

Abstract

As one of the rare single-phase multiferroic materials which have both ferroelectric and antiferromagnetic ordering at room temperature, BiFeO₃ has get a lot of attention in physics, material science and information storage technology. However, the ferroelectricity and magnetism of BiFeO₃ come from different ions. This leads to the contradictions in structure (especially in the electronic configuration of iron ion) between ferroelectricity and ferromagnetic order. Today various methods have been gradually improved to get pure-phase BiFeO₃，but weak magnetism in BiFeO₃ is still an important problem. Our research focuses on the study of the ion doped BiFeO_3。Compared to previous studies on BiFeO_3, this work explains the change of the electrical and magnetic properties of the ion doped BiFeO₃ by analyzing local structure and electronic hybridized orbit.

To study the influence of ion doped BiFeO₃ on the magnetic properties and local microstructures, polycrystalline BiFe_1-xCo_xO₃（x=0,0.01,0.03,0.05）samples were synthesized via sol-gel method. The structures of samples were observed by X-ray diffraction (XRD) and the magnetic properties were measured by Physical Property Measurement System (PPMS). We find the lattice structure of BiFeO₃ has not been changed by doping Co³ ions. It still is distorted perovskite structure. Co³ ions replacing the position of Fe³ ions enhance the ferromagnetism of BiFeO₃.Besides,the ferroelectric properties of BiFeO₃ has changed visibly by Co³ doping. It is better than others when x=0.01.

Key：multiferroic materials; BiFeO₃;Sol-gel method; Doping

目录

摘 要 I

Abstract II

第一章 绪 论 1

1.1 引言 1

1.2 多铁材料的分类 1

1.2.1 单相多铁材料 1

1.2.2 复合多铁材料 2

1.3 BiFeO₃的结构和基本性质 2

1.3.1 BiFeO₃的结构 3

1.3.2 BiFeO₃的基本性质 3

1.3.3 BiFeO₃的掺杂 4

1.4 本论文研究思路 5

参考文献 6

第二章 BiFeO₃的制备方法和表征技术 7

2.1 BiFeO₃的制备方法 7

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