Ce对烧结钕铁硼磁体永磁性的影响-中国材料进展

文章信息/Info

Title:: Effects of Cerium on Permanent Magnetic Properties of Sintered Nd-Fe-B Magnets

Keywords:: Ce mixed valence; CeFe2; Nd-Fe-B; sinter; rapidly quench; dual-alloy; dual-main-phase

摘要:: Ce在镧系元素中是具有特殊性质的一员，其根源在于它的混合价特性。在Ce2Fe14B化合物中，Ce表现出强烈的+4价倾向，不仅自身4f电子缺失无法贡献稀土离子磁性，而且离子半径过小导致Fe-Fe间距缩减，使Ce2Fe14B居里温度和饱和磁极化强度都以较大幅度下降。另外，在Ce-Fe-B三元合金中，Ce倾向于生成Laves相CeFe2，而非富稀土低熔点晶界浸润相，不能在烧结磁体中产生使主相晶粒退磁耦合的矫顽力机制，烧结Ce-Fe-B难以实现高矫顽力。尽管如此，Ce2Fe14B仍具有优良的内禀磁性，通过快淬方法可制备出性能适中的(Ce,Nd)-Fe-B各向同性磁粉，而通过贫Ce富Nd和贫Nd富Ce双合金或双主相烧结的方法，用富Nd相承担分割主相晶粒提高矫顽力的功能，也实现了高性价比(Ce,Nd)-Fe-B烧结磁体的商品化。本文针对Ce影响钕铁硼磁体内禀磁性和矫顽力方面的研究工作进行了综合阐述。

Abstract:: Cerium is a very special element in Lanthanide, originating from its mixed valence characteristics. Ce exists in Ce2Fe14B as Ce4+ ion. The lack of 4f electron leads Ce4+ to make no contribution to magnetism. Small ion radius shrinks the Fe-Fe distances and decreases the Curie temperature and saturation polarization of Ce2Fe14B. In addition, it is in favor of CeFe2 Laves phase instead of Ce-rich phase to magnetically decouple Ce2Fe14B grains. Sintered Ce-Fe-B magnet has very poor coercivity. Rapidly quenched isotropic (Ce,Nd)-Fe-B powder can realize reasonable HcJ for certain applications. By dual-alloy or dual-main-phase techniques, using Ce-rich/Nd-lean alloy and Nd-rich/Ce-lean alloy as starting materials, sintered (Ce,Nd)-Fe-B magnet is commercialized with high ratio of performance to cost. The key point is to let Nd-rich phase decouple (Ce,Nd)2Fe14B grains. This article reviews the effects of Cerium on the intrinsic and extrinsic magnetic peroperties of Nd-Fe-B permancent magnets.