Preparation And Characterization Of Bismuth Ferrite

Bismuth ferrite (BiFeO3) is a typical multiferroic material, which has applications in spintronic devices and sensors, information storage. BiFeO3(BFO) powders were synthesized by coprecipitation. The technological parameters for the pure BFO powders were obtained by X-ray diffraction (XRD) analysis; the photocatalytic of BFO powders, dielectric and magnetic propeties of BFO ceramics were analyzed; BFO thin films were prepared by sol-gel method and the magnetic propeties of BFO films were investigated. The main results and conclusions in this dessertation include the following parts:1. BFO powders with rhombohedrally distorted perovskite structre were obtained through a coprecipitaion process. The conditions for pure BFO powders were established:Bi content had an excess of 4～5%, pH>12, calcined at 500℃for 2h, the heating rates was 10～15℃/min, the size of the BFO powders were 30～90nm. UV-Vis absorption spectrum indicated that the energy bandgap is 2.05eV, which means that the response wavelength range is wide. During 3h UV irradiation,0.3 g BFO powders can make 4.8mg/L RhB aqueous solution (100 ml) to decolorize and its decomposition rate reach up to 96.4%.2. BFO ceramics were prepared through dry pressing and sintered at 850℃, in which uniform particle sizes in the range of 1～4μm. Dielectric constants (ε) was about 240,220,210 corresponding to the frequency of 1KHz, 10KHz and 100 KHz when the temperatures below 100℃.εrose markedly at high temperatures, and showed big differences among three frequencies. The spin magnetic structure make BFO ceramics not show ferromagnetic behavior, the magnetic hysteresis loop proves their anti-ferromagnetic properties.3. Pure BFO thin films were synthesized on the glass substrates by sol-gel and spin method.500nm thick BFO thin films with rhombohedrally distorted perovskite structre could be obtained by the following fabrication parameters:Bi3+:Fe3+= 1.05:1, the concentration of the precursor was 0.3M, calcined at 500℃, the numbers of spin-coated layers was 6. The surface of BFO thin films were smooth without microcracks, BFO thin films showed weak ferromangnetism at room temperature.