Hydrothermal Synthesis And Photics Properties Research Of Bi₂₅FeO₄₀ Powders

Materials of the sillenite family (B12MO20, M= Si, Ge, Ti) exhibit photics and thermallyinduced effects associated with changes in optical absorption, photorefractive and photoconductivity because of their special crystal structures. There are few reports about hydrothermal synthesis and photics properties of Bi25FeO4o powders until now. In this paper, Bi25Fe04o powders had been successfully synthesized by hydrothermal method. The photo-absorption, photoluminescence and photo-catalytic properties of Bi25FeO40 powders were also investigated.1) The pure phase of Bi25FeO40 powders was prepared by adjusting the conditions of hydrothermal synthesis such as concentrations of mineralizer, time and stoichiometry of reagents. NaOH, KOH and LiOH were chosen as mineralizers. With LiOH as mineralizer, the smaller particles were obtained.The hydrothermally growing mechanism and the structure of Bi25Fe04o powders were also studied. It was found that concentration of mineralizer and stoichiometry were related to the phase and morphology of as-prepared samples. When stoichiometry of reagents is changed, the pure Bi25Fe04o powders were obtained, which refered that the structure of Bi25FeO40 is stable with great openness.2) The band structure of Bi25Fe04o was calculated with Accelrys Material Sutido 4.0 CASTEP molde and the band-gap is 2.0eV. The valence band is mainly consisted of Bi 6s orbits, O2p orbits and part of Bi 6p orbits, while the conduct band is consisted of part of Bi 6p orbits.3) It was founded that Bi25FeO40 powders have good UV and visible light response in the wavelength of 200nm-600nm with analysis of UV-Vis diffuse spectrum, which is consistent with the result of calculation.The photoluminescence property was tested at room temperature. Excited wavelength is 350nm and Bi25Fe04o powders emit a blue band with the center of 469nm. The emission peaks are related with the band structure of Bi25Fe04o.4) Photo-catalytic activity of Bi25Fe04o powders was evaluated by the degradation of methyl violet solution under UV-Vis light irradiation. After irradating for 90min 90% of the methyl violet was degraded by the best sample. Bi25FeO40 is efficient for photo-degradation of the methyl violet owing to excellent absorption of UV-Vis light irradiation and its own crystal structure which benefits the separation of electron-hole.