Preparation And Magnetic Properties Of Multiphase Ferrite Materials Induced By Metal Iron

The hexaferrite is an important material which is widely used in microwave processing, and how to regulate the saturation magnetization and the coercivity of the hexaferrite in large range is a significant research topic in preparing this microwave processing materials, In this paper, spark plasma sintering (SPS) technique was used to synthesize a series of M-type, W-type and Z-type barium ferrites induced multiphase ferrite mateials in large range to regulate saturation magnetizations and coercivities with metal iron as an induced agent. The phase composition, crystallization reaction mechanism, microsturcture and magnetic properties of the multiphase ferrite materials were comprehensively studied.By regulating the SPS sintering temperature, holding time and pressure, the optimized condition is holding 30 min at 900℃and 20 MPa for synthesizing M-type barium ferrite (BaM) induced multiphase ferrite materials. M-type barium ferrite induced multiphase ferrite materials were synthesized by sintering the coprecipitation precursors with nominal composition of xFe + BaFe₁₂O₁₉(0≤x≤1,â–³x=0.1) under the optimized SPS condition. The multiphase ferrite mat1erials were composed of BaM, Fe₃O₄ and Ba₂Fe₁₄O₂₂ (Fe₂Y) for 03 and Fe(OH)₃ to form BaM, Fe(OH)₃ and Fe to form Fe₃O₄, BaM and Fe₃O₄ to form Fe₂Y; the multiphase ferrite materials were composed of Fe₃O₄ and Fe₂Y for 0.8≤x≤1.0, and the crystallization reaction is BaCO₃, Fe(OH)₃ and Fe to form Fe₂Y and Fe₃O₄. Needle Fe₂Y mainly occurred in the interface area between Fe₃O₄ and BaM. As the x increased, the saturation magnetization of the multiphase ferrite first reduced significantly and remained almost constant, finally remarkably decreased again and then slightly increased, the coercivity of the multiphase ferrite first increased significantly and then decreased slightly.A series of M-type, W-type and Z-type barium ferrite induced multiphase ferrite materials fabricated by sintering the mixtures of irons and single phase BaM, BaCo₂Fe₁₆O₂₇ (Co₂W) and Ba₃Co₂Fe₂₄O₄₁ (Co₂Z) powders with nominal composition of xFe+BaFe₁₂O₁₉, xFe + BaCo₂Fe₁₆O₂₇ and xFe + Ba₃Co₂Fe₂₄O₄₁ (0≤x≤1,â–³x=0.1) using SPS method at 900℃and 20 MPa holding for 30 min, respectively. To the M-type barium ferrite induced multiphase ferrite materials, the grain size, the saturation magnetization and the coercivity reduced gradually, but the density increased with the x increasing. The crystallization reaction is BaM and Fe to form Fe₂Y and Fe₃O₄, when multiphase ferrite materials were composed of BaM, Fe₃O₄ and Fe₂Y; the crystallization reaction are BaM and Fe to form Fe₂Y and Fe₃O₄, Fe and Fe₂Y to form BaFe₂O₄ and Fe₃O₄, when the multiphase ferrite materials were composed of Fe₃O₄, Fe₂Y and BaFe₂O₄. To the W-type barium ferrite induced multiphase ferrite materials, the density increased, the saturation magnetization reduced and the coercivity increased and then reduced with the x increasing. The crystallization reaction is Co₂W and Fe to form Ba₂Co₂Fe₁₂O₂₂(Co₂Y), CoFe₂O₄ and Fe₃O₄ when multiphase ferrite materials were composed of Co₂W, Fe₃O₄, Co₂Y and CoFe₂O₄; the crystallization reaction are Co₂W and Fe to form Co₂Y, CoFe₂O₄ and Fe₃O₄, Fe and Co₂Y to form BaFe₂O₄, Fe₃O₄ and CoFe₂O₄ when the multiphase ferrite materials were composed of Fe₃O₄, Co₂Y, BaFe₂O₄ and CoFe₂O₄. To the Z-type barium ferrite induced multiphase ferrite materials, the density and the coercivity increased but the saturation magnetization reduced with the x increasing. The multiphase ferrite materials were composed of Co₂Z, Fe₃O₄, BaFe₂O₄ and Co₂Y, the Co₂Z disappeared with x=1.0. The crystallization reaction mechanism is Co₂Z and Fe to form Co₂Y, Fe₃O₄ and BaFe₂O₄.