【作者】 吴晓艳；

【导师】 赵文俞；

【作者基本信息】 武汉理工大学 ， 材料学， 2009， 硕士

【摘要】 六角铁氧体是一种广泛应用在微波信号处理领域的重要材料,如何大幅度调控饱和磁化强度和矫顽力一直是此类材料研究的重点。本文以金属铁作为诱发剂、采用放电等离子体烧结（SPS）技术制备了一系列饱和磁化强度和矫顽力均可大幅度调控的M型、W型和Z型钡铁氧体诱变复相铁氧体材料,重点研究了复相铁氧体的物相组成、结晶反应机制、显微结构和磁性能。通过优化SPS烧结的温度、保温时间和压力,确定了制备M型钡铁氧体（BaM）诱变复相铁氧体材料的优化SPS工艺为900℃、保温30 min和压力20MPa。利用该工艺,以名义组成为xFe+BaFe₁₂O₁₉（0≤x≤1.0,△x=0.1）的共沉淀前驱体制备了BaM诱变复相铁氧体材料。0<x<0.8时复相铁氧体由BaM、Fe₃O₄和Ba₂Fe₁₄O₂₂（Fe₂Y）组成,结晶反应为BaCO₃与Fe（OH）₃生成BaM,Fe（OH）₃与Fe生成Fe₃O₄,BaM与Fe₃O₄生成Fe₂Y;0.85≤x≤1.0时复相铁氧体由Fe₃O₄和Fe₂Y组成,结晶反应为BaCO₃、Fe（OH）₃与Fe生成Fe₃O₄和Fe₂Y。针状Fe₂Y主要分布在Fe₃O₄和BaM之间的界面区。随着x增加,复相铁氧体的σ_s呈先显著降低后几乎不变、再显著降低和缓慢增大现象,H_c呈先大幅度降低后略增大现象。在900℃、保温30 min和20 MPa的SPS条件下,分别用金属铁粉与单相BaM、BaCo₂Fe₁₆O₂₇（Co₂W）和Ba₃Co₂Fe₂₄O₄₁（Co₂Z）粉体构成的xFe+BaFe₁₂O₁₉、xFe+BaCo₂Fe₁₆O₂₇和xFe+Ba₃Co₂Fe₂₄O₄₁（0≤x≤1.0,△x=0.1）的均匀混合物制备了系列M型、W型和Z型钡铁氧体诱变复相铁氧体材料。BaM诱变复相铁氧体随x增加其晶粒尺寸、瓯和皿逐渐减小但致密度逐渐增大,物相组成为BaM、Fe₃O₄和Fe₂Y时结晶反应为BaM与Fe生成Fe₂Y和Fe₃O₄,为Fe₃O₄、Fe₂Y和BaFe₂O₄时结晶反应为BaM与Fe生成Fe₂Y和Fe₃O₄,Fe与Fe₂Y生成BaFe₂O₄和Fe₃O₄;CO₂W诱变复相铁氧体随x增加其致密度逐渐增大、σ_s逐渐降低、H_c先增大后降低,物相组成为Co₂W、Ba₂Co₂Fe₁₂O₂₂（Co₂Y）、CoFe₂O₄和Fe₃O₄时结晶反应为Co₂W与Fe生成Co₂Y、CoFe₂O₄和Fe₃O₄,为BaFe₂O₄、Fe₃O₄、CoFe₂O₄和Co₂Y时结晶反应为Co₂W与Fe生成CoFe₂O₄、Co₂Y和Fe₃O₄,Fe与Co₂Y生成BaFe₂O₄、Fe₃O₄和CoFe₂O₄;Co₂Z诱变复相铁氧体随x增加其致密度和H_c增大、σ_s降低,物相组成由Co₂Z、Fe₃O₄、BaFe₂O₄和Co₂Y组成,但x=1.0时Co₂Z消失,结晶反应为Co₂Z与Fe生成Co₂Y、Fe₃O₄和BaFe₂O₄。更多还原

【Abstract】 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,△x=0.1） under the optimized SPS condition. The multiphase ferrite mat1erials were composed of BaM, Fe₃O₄ and Ba₂Fe₁₄O₂₂ （Fe₂Y） for 0<x<0.8, and the crystallization reaction are BaCO₃ 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,△x=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.更多还原