Template-free Growth And Characterization Of Low-Dimensional Bi₂Fe₄O₉ Nano-materials By Hydrothermal Synthesis

is an important functional material because of its potential applications as semiconductor gas sensor and good catalyst. Nano-sized Bi2Fe4O9 shows electrical, magnetic and optical properties different from bulk materials. The research of Bi2Fe4O9 started in recent years. At present, it is difficult to get the pure Bi2Fe4O9 because they required complex synthesis conditions. There have few reports about the control of phase and morphology. In this dissertation, Bi2Fe4O9 were chosen as the object of study. We studied systematically the effect of hydrothermal parameters and try to control of the structure and properties. The obtained main results are as follows:Pure nano-sized Bi2Fe4O9 has been preparation via template-free hydrothermal method, with NaOH and KOH as the mineralizer, respectively. Through varying the hydrothermal parameters variety morphologies Bi2Fe4O9 is prepared. The optimum hydrothermal processing conditions for Bi2Fe4O9 nanobelts of orthorhombic structure characterized by even size and morphology and well crystallization are:the concentration of NaOH of 12 M, the hydrothermal time of 24 h, the hydrothermal temperature of 200℃. When CKOH 12 M, nanowire Bi2Fe4O9 with regular morphology are synthesized after the precursor was heated at 200℃for 24 h.The growth mechanism of Bi2Fe4O9 was investigated by studying the influence of hydrothermal temperature, reaction time and mineralizer concentration, especially, on the structure and morphology of the products. It has been suggested that the presence of the OH- ions may promote the formation of crystal growth. The difference of adsorption capacities of various crystal planes leads to the differences of growth speed. In the addition, Na+ and K+ also have a pronounced effect certain various morphologies.The relationship between properties and structure of the bismuth ferrite had been validated by some testing methods. The dielectric constant and dielectric loss 9 are lower after it is applied bias. The J-V curves shows that the leakage current density of Bi2Fe4O9 is stable. With the UV-Vis spectra, Bi2Fe409 powders have a broad absorption band in the range of 200-350 nm and a good visible-light-response ability.