Study On Synthesis And Magnetism Of Flake Shaped BaFe₁₂O₁₉

In this thesis, firstly, In the design ideology, Barium ferrite was synthesized via coprecipitation method with different raw materials prepared by coprecipitation method and EDTA so/gel method, respectively. The results can show the seed of BaFe₁₂O₁₉ crastal growth along radial aspect and the size of it is micron. Secondly, we make it and analyse the process of the reaction. Thirdly, According to the process, different methods can influence the magnetic property.The product of BaFe₁₂O₁₉ crastal had been prepared by the-second coprecipitation method using the seed crastal and the size of the particle is 0.4-2μm, the diameter-to-thickness ratio is 4-20. The shape of the product is hexagonal platelet-like and the size of it is micron. The research methods, which consisted of XRD,IR,TG/DTA,SEM/EDS, were used to character the structure of the crystal, photograph, and thermal performance. From the results, it was shown that the precursor was the complex substance of the non-crystalline BaCO₃,the low- crystalline Fe(OH)₃ and the crystallineα-Fe₂O₃ adsorption on the seed crastal BaFe₁₂O₁₉ when preparing the product of BaFe₁₂O₁₉ by the-second coprecipitation reaction methods. The final product BaFe₁₂O₁₉ crystal was obtained by the process describing as following: firstly, losing H2O from Fe(OH)₃; secondly, then decomposition of BaCO₃; thirdly, formation of mesophasesα-Fe₂O₃ and BaO; and finally synthesis of the BaFe₁₂O₁₉ crystal. Based on the formation process of BaFe₁₂O₁₉, we discussed the influences of the main synthesized conditions as the consistency and time of the reaction to the final products, from the results, it was shown that under the proper consistency and the long time of reaction, and we can get the better magnetic property of BaFe₁₂O₁₉.Under optimum conditions for sythesis to obtain the seed of BaFe₁₂O₁₉ crastal by EDTA so/gel method, and the product of BaFe₁₂O₁₉ crastal had been prepared by EDTA so/gel—coprecipitation method using the seed crastal and the size of the particle is 0.8-1.5μm, the diameter-to-thickness ratio is 4-8. The research methods, which consisted of XRD,IR,TG/DTA,SEM/EDS, were used to character the structure of the crystal, photograph, and thermal performance. From the results, it was shown that the precursor was the complex substance of the non-crystalline BaCO₃,the low- crystalline Fe(OH)₃ and the crystallineα-Fe₂O₃ adsorption on the seed crastal BaFe₁₂O₁₉ when preparing the product of BaFe₁₂O₁₉ by coprecipitation reaction methods. The final product BaFe₁₂O₁₉ crystal was obtained by the process describing as following: firstly, losing H2O from Fe(OH)₃; secondly, then decomposition of BaCO₃; finally synthesis of the BaFe₁₂O₁₉ crystal.Contrast to the process of the platelet-like barium ferrite was prepared by the second coprecipitation method and EDTA so/gel—coprecipitation method. The research result , which consisted of XRD,IR,SEM/EDS and TG/DTA-MS, were shown as follows. Firstly,the content of the precursor is more and the coating substance on precursor was dispersed more even by the second coprecipitation method; Secondly, the thermal behavior of Fe(OH)₃ was basically unanimous, nevertheless the decomposition reaction of BaCO₃ was different by the second coprecipitation method. Thirdly, the thermal reaction make the purity,crystallization and diameter-to-thickness ratio better by the second coprecipitation method.According to the VSM results, it can show that the coercive force (Hc)of the products was higer by coprecipitation method than the raw materials, the saturation intensity(Ms) and remanent magnetization(Mr) were lower by the second coprecipitation method, howerer these were higer by the EDTA so/gel—coprecipitation method. The Hc, the Ms and Mr of the products were higer by EDTA so/gel—coprecipitation method than the second coprecipitation. It all shows the method by the coprecipitation on the raw materials of BaFe₁₂O₁₉ crystal can improve the magnetic of BaFe₁₂O₁₉.