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Preparation and Characterization of Fe-based Oxides Narrow Bandgap Semiconductors

Author: ZhangTong
Tutor: HongZhangLian
School: Zhejiang University
Course: Materials Physics and Chemistry
Keywords: Narrow - band -gap semiconductors Visible Photocatalytic BiFeO3 SiO2/YFeO3 Bi5Ti3FeO15
CLC: TN304
Type: Master's thesis
Year: 2010
Downloads: 210
Quote: 0
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Abstract


In recent years, the semiconductor photocatalytic technology at the air / water purification clean, harmful pollution control and other aspects of significant value are of great concern and extensive research, is the solution to industrial development an important pollution of the global environmental pollution problems caused by control technology. Among them, the development of efficient semiconductor photocatalyst is one of the key technology. Currently, there are two broad categories of semiconductor photocatalyst: one is based on TiO , 2 is represented by the traditional semiconductor material and the doping system; the other is the new composition of the narrow band gap semiconductor materials. Compared with the traditional TiO 2 wide band gap material, a narrow band gap semiconductor material because it can effectively absorb the energy of sunlight visible band characteristics can be used to the visible degradation of organic matter and water photolysis Hydrogen and other outstanding features, become a hotspot of research and development of new semiconductor materials. In the narrow band gap semiconductor preparation and research progress on the basis of preparation around the iron-based semiconductor materials, structure characterization and properties of conducting research, hydrothermal method using solid-phase method and sol-gel method the the BiFeO of the perovskite structure 3 , the SiO 2 / YFeO 3 complexes and Aurivillius Compounds the Bi 5 Ti 3 FeO 15 ; focusing on the process conditions on the ratio of raw materials, the reaction temperature, holding time, the number of coated synthetic samples phase synthesis law, phase structure and species, as well as synthetic product under visible photocatalytic degradation of methyl orange (MO) characteristics of the effect; the the nanometer dimensions Bi 5 the Ti 3 FeO of 15 hydrothermal synthesis route, semiconductor characteristics and magnetic properties were analyzed and characterized. The first part of the thesis, based on the Bi 2 O 3 , the Fe 2 O 3 , nitrate as raw material, solid-phase method and hydrothermal prepared the BiFeO 3 of the research work. Solid-phase synthesis process, focusing on the ratio of raw materials, visible light photocatalytic performance of the types of raw materials and sintering temperature on the synthesis of pure phase the BiFeO 3 of the impact of the law, as well as product. Meanwhile, in the supporting role of the mineralizing agent hydrothermal conditions synthesized the BiFeO 3 ; and solid-phase method and hydrothermal synthesis of BiFeO 3 phase formation conditions , as well as products in the visible light photocatalytic performance differences were compared and analyzed. The results show that using solid phase method synthesis of BiFeO 3 when the increase in raw material bismuth / iron ratio, are more prone to BI 25 FeO of 40 Miscellaneous ; fixed bismuth / iron ratio of 1:00, reaction temperature on the purity of the product have a major impact, increasing the reaction temperature the prone Bi 2 the Fe 4 O 9 miscellaneous-phase. In addition, the the nano Fe 2 the O 3 particles as a raw material, the analysis with the solid-phase reaction nano the Fe 2 the O 3 < / sub> easy and Bi 2 O 3 mixed raw material particles surface energy of the solid phase reaction-diffusion rate increases and other factors. On this basis, access to the single phase BiFeO of Solid Phase Synthesis of impurities less 3 The optimum conditions: raw material bismuth / iron ratio of 1:1, and incubated for 3h in the 830 ° C temperature. Hydrothermal Synthesis the BiFeO 3 process, increasing the reaction temperature, or an increase in the reaction temperature holding time in the holding time conditions, are conducive to the promotion of BiFeO 3 generated. The photocatalytic efficiency test results show that solid phase synthesis contains impurities the BiFeO 3 product, visible catalytic efficiency is better than the hydrothermal synthesis of pure-phase BiFeO 3 , photocatalytic efficiency . The reason for this difference may be related to miscellaneous auxiliary the BiFeO 3 degradation mechanism of MO photocatalytic performance level with the BiFeO 3 product particles shaped developmental state and crystal lattice defects. The second part of the thesis work is Pechini sol - gel method, the amorphous SiO 2 microspheres the composite YFeO 3 . YFeO 3 precipitation coated precursor solution prepared by the different number of coated SiO 2 / YFeO 3 complexes of different coated The times on SiO 2 / YFeO 3 complex morphology, degradation of MO process and degradation kinetics of visible light catalytic performance of law, and the number of coated products. It was found that the increase in the number of coated, the product visible light photocatalytic degradation of MO efficiency. The third part of the work by the hydrothermal method and prepared by solid Aurivillius Compounds Bi 5 Ti 3 FeO 15 . Increase the holding time conditions, the product Bi 5 the Ti 3 FeO 15 phase formation process and structure in the process of hydrothermal method proved evolution. In the process, the solid phase method, by changing the sintering temperature obtained by the synthesis of single-phase Bi 5 the Ti 3 FeO 15 of the preferred sintering conditions. The study found that the process of hydrothermal method 200 ° C insulation 48h, solid-phase method at 900 ℃ for 5 hours, can be prepared by a single-phase Bi 5 Ti 3 FeO 15 . The product Bi 5 the Ti 3 FeO 15 In addition to the semiconducting at room temperature exhibit paramagnetic properties.

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