Sm_2Co_(17)基高温稀土永磁材料的显微结构与磁性

MICROSTRUCTURE AND MAGNETIC PROPERTIES OF Sm_2Co+(17)-BASED HIGH TEMPERATURE PERMANENT MAGNETS

Cu含量较高的Sm2Co17基永磁材料在高温下具有较大的内禀矫顽力,而Fe含量较高时其高温下的磁性较差. TEM显示磁体由胞状结构构成,胞内为2:17R相,胞壁为1:5相.在MFM(磁力显微镜)下可观测到片状相(1:7相), 畴结构为波纹畴和条状畴,但是在片状相出现的区域并未观察到畴壁钉扎点,而在胞壁相的三角结合区域畴壁的钉扎强度最高.高温X射线衍射分析表明,随着性能的降低观测到材料的相结构发生了较大的变化,由室温下的2:17R主相、1:5相和1: 7相变为非晶结构,且最终转变成700℃时的SmCo3主相和2:17R相.相结构的转变直接导致磁体性能的降低.

High temperature Sm2Co17-based permanent magnets have been attained and the microstructures have been investigated by TEM, MFM and high-temperature XRD. The coercivity of the magnets at high temperature gradually increases with increasing Cu content, but decreases with Fe content increasing. The magnet has a cellular structure consisting of 2 ： 17R phase in cell interior and 1 ： 5 phase at cell boundary. Lamellar phase （1 ： 7 phase）, wavy domain wall and strip domain wall can be found by MFM. But no distinctive domain wall pinning sites along the lamellar phase were observed. At the triple junction of cell boundaries, the domain wall pinning strength is the highest.XRD shows that 2 ： 17R, 1 ： 5 and 1 ： 7 phases are transformed into amorphous phase at 500 ℃,and ultimately SmCo3 and 2 ： 17R formed at 700 ℃, accompanied by a degradation of magnetic properties of the magnets.