Fabrication Of Cobalt Doped Anatase Powders And Their Properties

The study background and application perspectives of DMS are introduced. Some of basic properties of DMS and TiO₂, such asmagnetic effect origin of ferromagnetism are also reviewed. Based on adequate study of background knowledge, we choose the preparation and magnetism as well as photocatalysis under magnetic field of the Co doped TiO₂ specimens to research.Co-doped anatase powders were fabricated using Sol-gel method. After selecting synthesis method based on the XRD and magnetization measurement, degradations of Rhodamine B using optimized specimens were placed to study the change of band structure under magnetic field. The main content of the thesis is as follows:First, specimens with room temperature ferromagnetic properties were obtained through optimized preparation process. No impurity phase besides anatase was detected by XRD measurement. The magnetization moments under magnetic field of 1.5T increased with escalating cobalt dopant.Semiconductor properties were studied by analysing the UV-VIS and PL spectrums of the specimens with different doping concentration. It is found that defect levels origins from cobalt dopant and surface defect made the red shift of energy band edge. Otherwise, compared with pure TiO₂ synthesized from similar preparation process, specimens with cobalt dopant had narrower band gap, indicating the existence of magnetic ordered structure.It is also found that the effect of magnetic field(0.1T) on the degradation of Rhodamine B during photocatalysis processes using spencimens of different doping concentration was not of the same trend. This phenomenon was contributed to two factors. First, the spin splitting out of magnetic field made the energy band edge shifted nearer the main wavelength of the lamp, so the absorption of optical energy increased; second, with escalating cobalt dopant, the exchange coupling between Co²⁺ and carriers was enhanced, making more carriers localized, so there were less electron-hole couples emitted by photons.