The Preparation And Properties Of Ferrite Bismuth And Its Compsite Materials

Multiferroic materials are characterized by simultaneous coexistence of two or more kind of ferroelectric,(anti)ferromanetic and ferroelasticity. BiFeO3showing multiferroic properties materials at room temperature rarely and having widely potential applications, caused much attention of many scholars. Therefore, we selected the ferrite bismuth and its composite material as the research object. The process conditions of bismuth ferrite powders syntheized by molten salt methods, the superfine strontium titanate powder prepared by hydrothermal technology and the preparation technology of the composite material have carried out the detailed research in this thesis. The effects of strontium titanate content on the properties of bismuth ferrite-based composites were investigated. This paper main content is as follows:(1) The introduction focuses on the definition, classification and basic properties of multiferroic materials, research status of the BiFeO3and the causes of choosing this topic, and determined the research content.(2) The single-crystalline BiFeO3submicron powder was successfully synthesized by molten salt (KCl-KBr) using BiO3and Fe2O3as raw materials. The effects of different kinds of molten salt, the mass ratio of molten salt and raw materials, calcination temperature and calcination time on the preparation BiFeO3were investigated. The results revealed that the single crystalline BiFeO3powder with rhombohedral structure can be obtained by using molten salt (KC1-KBr) from750to800℃as the mass ratio of molten salt and raw materials as1.0. The average particle size of the BiFeO3powder is about0.6μM. The formation mechanism of BiFeO3synthesized by molten salt method is discussed, based on template formation mechanism.(3) The superfine strontium titanate (SrTiO3) particles was successfully synthesized by hydrothermal method using K2TiO(C2O4)2-2H2O, Sr(NO3)2as raw materials and NaOH as mineralizer. The effect of the molar ratio of mineralizer and raw materials, hydrothermal temperature and hydrothermal time, etc. on the preparation superfine BiFeO3V powder was investigated. The as-prepared samples were examined by X-ray powder diffraction (XRD) for phase identification, and scanning electron microscopy (SEM) for particle microstructure anlysis. The results show that the single phase of SrTiO3can be obtained at200℃for12h as the molar ratio of raw materials and mineralizer was1:6. The hydrothermal temperature is the main reason which affected the crystal growth rate.(4) Using the superfine SrTiO3powder prepared by hydrothermal method and the submicron BiFeO3powder synthesized by molten salt method as the starting materials, the (1-x)BiFeO3-xSrTiO3(0.00<x<1.00) composite were prepared at different sintering temperature by adding the sintering additive (Bi2O3) and adhesive (PVA), and then tableting. The sintering process affecting to the (1-x) BiFeO3-xSrTiO3composites’ relative density was investigated. The strontium titanate content impacting to (1-x)BiFeO3-xSrTiO3composite phase composition, dielectric constant, dielectric loss and ferroelectric properties were discussed in detail. The results show that, in the preparation process of (1-x) BiFeO3-xSrTiO3composite material, the optimum sintering temperature increases with the strontium titanate content increasing and the optimum temperature range from780to950℃. It is found that the structure phase of samples transsiton an anti-ferromagnetic rhombohedron structure (R3c) to the non-magnetic cubic phase structure with the strontium titanate content increasing when the x value is range from0.00to0.30. the bismuth ferrite and strontium titanate are coexistence when the x value is range from0.35to1.00. Dielectric properties, ferroelectric properties and ferromagntic properties tests show that the incorporation SrTO3help to improve the dielectric properties, ferroelectric properties and ferromagnetic properties of the sample.