Study On Preparation And Properties Of Multiferroic BiFeO₃by Hydrothermal Method

Multiferroics, defined as materials with coexistence of at least two characteristics of ferroelectric, ferroelastic, and ferromagnetic. As a typical single-phase multiferroic, Bismuth ferrite (BiFeO3) of perovskite structure has attracted renewed and ever increasing research interest during the past several years, which could be widely applied to such as Filter, Sensor, Performor, Executor, Information storage and Non-linear optical hardware. The main problems of study on BiFeO3can be concluded: the origin of high polarization, the relation of magnet-electricity to structure, synthesis method is complicated and pure phase sample is difficult to obtain and so on. Hydrothermal has many advantages in synthesis of ferroelectrics, such as simple device, easier composition control, and better homogeneity. It is a useful method and can be used in synthesis of BiFeO3.In this dissertation, stabilized BiFeO3powder is synthesized using hydrothermal method and the influencing factor is analyzed. Based on the successful synthesis by hydrothermal method, B site of BiFeO3doped by Cr is studied. The phase structure, surface morphology, electrical properties and magnetic properties are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and impedance analyzer (Angilent) respectively. The results are as follows:1. The condition of140℃0.3mol/L and12h can synthesize pure BiFeO3powders and the size of powders are3μm.2. The phase structure and microscopic appearance of BiFeO3ceramic sintered under830℃was better. The dielectric spectrum and temperature dependent of dielectric-temperature are better for BiFeO3ceramics also. The ferroelectricity and ferromagnetism property of BiFeO3under room temperature is weak.3. BiFe1-xCrxO3samples are synthesized by hydrothermal. With the increase amount of doping Cr, the structure of BiFeO3is changed. 4. The microscopic structure of sintered BiFe1-xCrxO3is better. With the increase amount of doping Cr, the size of powders is reduced. Compared with BiFeO3, the dielectric, dielectric-temperature and ferroelectricity characteristics have no change, but the ferromagnetic is improved.