二价铁过量M型钡铁氧体的放电等离子体烧结合成

在氩气保护下用化学共沉淀工艺制备了名义组成为BaFe³⁺_11.8Fe²⁺_0.3O₁₉的Fe²⁺过量M型钡铁氧体（BaM）前驱体，采用XRD、SEM和Archimedes法研究了前驱体在放电等离子体烧结（SPS）条件下的物相组成、显微结构和致密度. 结果表明，合成高致密度的单相Fe²⁺过量BaM材料的优化SPS工艺为850℃、保温30min和压力10MPa，其结晶机制为低温下前驱体分解形成α-Fe₂O₃和Fe₃O₄或γ-Fe₂O₃，高温下Fe²⁺过量BaM结晶，整个结晶过程中没有BaFe₂O₄中间相形成. 单相Fe²⁺过量BaM材料的饱和磁化强度为58.2A·m²·kg^-1，矫顽力为255kA·m^-1， 说明Fe²⁺占据自旋向上的2a磁晶位.

M-type Barium Hexaferrite with Excessive Divalent Iron Synthesized by Spark Plasma Sintering Method

The precursor of M-type barium hexaferrite (BaM) with excessive divalent iron BaFe³⁺_11.8Fe²⁺_0.3O₁₉ was prepared by chemical coprecipitation process in Ar atmosphere. The phase compositions, microstructures, and densities of sintered products synthesized by spark plasma sintering (SPS) method were investigated with XRD, SEM and Archimedes methods. The optimizing SPS condition for synthesizing single phase and high compactness BaM materials with excessive divalent iron is holding for 30min at 850℃ and 10MPa. The crystalline reaction process is composed of the decomposition of the precursor into α-Fe₂O₃ and Fe₃O₄ or γ-Fe₂O₃ at low temperature and the crystallization of BaM with excessive Fe²⁺ at high temperature, without intermediate phase BaFe₂O₄ forming in the whole process. Saturation magnetization and coercivity of single phase BaM materials with excessive divalent iron are of 58.2A·m²·kg^-1 and 255kA·m^-1, respectively, which imply that the excessive divalent irons spin upward at 2a site in FeO₆ octahedron.