Influence of additional compounds on coercivity of sintered Nd-Fe-B magnets

Thanh Pham,Dan Nguyen,Mashirov Alexey,Kamantsev Alexander,Ngoc Nguyen,Quang Dinh,Lam Nguyen,Yen Nguyen,Koledov Victor,Duong Nguyen,N Perov,A Semisalova

doi:10.1051/epjconf/201818504031

Abstract

In this paper, we investigated the influence of additional compounds of Dy-Nb-Al, Nd-Cu-Al… on the coercivity of the sintered Nd16.5Fe77B6.5 magnets. The additional compounds were first prepared by arc-melting method and then ground into particles with size in the range of 40 - 80 nm using a high energy ball milling method. After that, the additional powder were mixed with micrometer Nd-Fe-B powder before magnetic anisotropic pressing, vacuum sintering and annealing. The structure of the magnets was thoroughly analyzed using X-ray diffraction and electron microscopy techniques. The magnetic properties of the magnets were investigated on a pulsed field magnetometer. The results show that the coercivity of the sintered Nd-Fe-B magnets can be improved by introducing additional nanoparticles to their grain boundaries. The improvement of the coercivity of the magnets is clearly dependent on composition and fraction of the additional compounds. The coercivity has been enhanced 40% for the magnets by adding 3 wt% of the Dy-free compound of Nd40Cu30Al30.

Highlights

Due to excellent magnetic properties such as the high saturation magnetization (Ms = 16 kOe) and large magnetocrystalline anisotropy (HA = 75 kOe) of the Nd2Fe14B phase, the sintered Nd-Fe-B magnets are widely applied in practice [1, 2]
We investigated the influence of additional compounds of Dy-Nb-Al, Nd-CuAl... on the coercivity of the sintered Nd16.5Fe77B6.5 magnets
The structure of the magnets was thoroughly analyzed using X-ray diffraction and electron microscopy techniques

Summary

Introduction

Due to excellent magnetic properties such as the high saturation magnetization (Ms = 16 kOe) and large magnetocrystalline anisotropy (HA = 75 kOe) of the Nd2Fe14B phase, the sintered Nd-Fe-B magnets are widely applied in practice [1, 2]. With addition of compound containing Dy, the coercivity is considerably increased by the formation (Nd,Dy)2Fe14B phase with high magnetocrystalline anisotropy. Other research results have been confirmed that both of Al and Cu do not enter the Nd2Fe14B phase, the intrinsic properties (Ms and HA) of the Nd2Fe14B grains remain unchanged. These elements of Al and Cu mainly help to improve microstructure such as uniform distribution of grain boundaries, controlling of the particle size. The influence of the additional compounds of Dy-Nb-Al, Nd-Cu-Al... on the coercivity of the sintered Nd-Fe-B magnets was investigated

Experimental

Results and discussion

M B BH

Conclusion