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-likeα-Fe₂O₃,shuttle-likeα-Fe₂O₃ and acicularα-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-likeα-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-likeα-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-likeα-Fe₂O₃ are better than those of specimens obtained using shuttle-likeα-Fe₂O₃.For the experiments using acicularα-FeOOH as Fe sources,it was found that the structural and magnetic properties of SrM were affected by the different hydrothermal temperatures ofα-FeOOH.The specimens exhibited a high saturation magnetization.The specimen obtained at a sintering temeperature of 1200°C and usingα-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 acicularα-FeOOH and commercialα-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 usingα-FeOOH as Fe sources.When the sintering temperature is 1250°C and the mass ratio ofα-Fe OOH:α-Fe₂O₃ is 7:3,the specimen exhibited the best magnetic properties（saturation magnetization:71.9 emu/g;coercivity:139.2 kA/m）.