Preparation And Magnetic Properties Of Hexagonal M-type SrFe₁₂O₁₉ Ferrite Obtained By Using Different Iron Sources

Hexagonal M-type SrFe₁₂O₁₉?SrM?ferrite is widely-used due to its high coercivity and fine cost performance.Currently,how to improve the magnetic properties of SrM ferrite is still a hot research topic.In this thesis,cubic-like?-Fe₂O₃,shuttle-like?-Fe₂O₃ and acicular?-FeOOH were obtained via a hydrothermal method.Then,SrM ferrites were obtained by using these different iron sources via a ceramic method,and the effects of different iron sources and sintering temperatures on the phase composition and magnetic properites were studied.For the experiments using cubic-like and shuttle-like?-Fe₂O₃ as Fe sources,it was found that with the increase of sintering temperature from 1200°C to 1300°C,the saturation magnetization and coercivity of SrM specimens present an increasing and decreasing trend,respectively.When the sintering temperature is 1300°C,the saturation magnetization of SrM specimen obtained using cubic-like?-Fe₂O₃ is 66.4 emu/g,while the coercivity decreased rapidly to 12.4 kA/m due to the abnormal growth of?008?lattice plane.In general,the magnetic properties of specimens obtained using cubic-like?-Fe₂O₃ are better than those of specimens obtained using shuttle-like?-Fe₂O₃.For the experiments using acicular?-FeOOH as Fe sources,it was found that the structural and magnetic properties of SrM were affected by the different hydrothermal temperatures of?-FeOOH.The specimens exhibited a high saturation magnetization.The specimen obtained at a sintering temeperature of 1200°C and using?-FeOOH with a hydrothermal temperature of 180°C had a maximum saturation magnetization of 76.7 emu/g,while its coercivity dereased markedly.For the experiments using both acicular?-FeOOH and commercial?-Fe₂O₃ as Fe sources,the saturation magentiztion and coercivity of SrM specimens presented an increasing and decreasing trend,respectively,compared with those of specimens only using?-FeOOH as Fe sources.When the sintering temperature is 1250°C and the mass ratio of?-Fe OOH:?-Fe₂O₃ is 7:3,the specimen exhibited the best magnetic properties?saturation magnetization:71.9 emu/g;coercivity:139.2 kA/m?.