Study On Preparation And Properties Of The Multiferroic BiFeO₃-based Compounds

Multiferroic materials, which simultaneously exhibit two or more ferroic natures(such as ferroelectricity, ferromagnetism), and more importantly, magnetoelectric coupling effect, have stimulated increasing interest in research for the novel devices such as actuators, sensors, transducers and memories. As a representative single-phase multiferroic material, perovskite-type BiFeO₃ (BFO) may exhibit ferroelectric and antiferromagnetic properties simultaneously at room temperature. In view of the defects of BFO, in this dissertation, we mainly report the preparation of BFO and the effects of La doping and magnetic field on the structure and properties of BFO. Main works are as following:Chapter 1: Introducing the history and present status of research on multiferroic materials. Discussing the structure, properties and existed problems of multiferroic material BFO.Chapter 2: In view of volatilty of Bi, preparation of BFO by choosing different ratio of Bi:Fe and Bi_1-xLa_xFeO₃ with x=0, 0.05, 0.1, 0.15, 0.2, and obtainng the best content with Bi at x=1.02) and La at x=0.1.Chapter 3: Preparing Bi_0.9La_0.1FeO₃ ceramics in the magnetic field of 0.5T and 0T by solid reaction, respectively. It is found that the compactness of samples is improved, particle scale is minished, and, polarization of BLFO is improved correspondingly.Chapter 4: Preparing the compound of Bi_0.9La_0.1FeO₃ and CoFe₂O₄ (CFO) by solid-phase reaction in the magnetic field of 0.4T and 0T respectively. By analyzing it is found that the ferroelectric and magnetic properties are improved greatly.Chapter 5: Summarizing the previous work, and looking for the future word briefly.