Enhanced coercivity of Nd-Ce-Fe-B sintered magnets by adding (Nd, Pr)-H powders

Abstract

Incorporating the highly abundant rare earth (RE) Ce into Nd-Fe-B sintered magnets has attracted considerable interest recently. The inferior anisotropic field (HA) of Ce2Fe14B to Nd2Fe14B, however leads to low coercivity of the Nd-Ce-Fe-B magnets. To further enhance the coercivity, in this work, (Nd, Pr)-H powders were used as intergranular additive to restructure the grain boundaries of the low cost (Nd,Pr)22.3Ce8.24FebalB1 (wt.%) sintered magnets. When added with only 2 wt% (Nd, Pr)-H, the Hcj can be enhanced from 10.6 kOe to 12.7 kOe with slight reduction in remanence and maximum energy product. The dehydrogenation of (Nd, Pr)-H during sintering promotes the diffusion of Nd and Pr towards the 2:14:1 phase grains and the smoothing of grain boundaries. The formation of (Nd, Pr)-rich shell with locally enhanced magnetocrystalline anisotropy and the magnetic isolation between adjacent 2:14:1 phase grains result in obvious coercivity enhancement, which was supported by magnetic domain structure characterizations and micromagnetic simulations. It suggests that through grain boundary restructuring, the coercivity of Nd-Ce-Fe-B magnets can be enhanced to be comparable of commercial Nd-Fe-B magnets, which may shed new insights into the fabrication of low cost RE permanent magnets.