Coercivity enhancement of Nd-Fe-B sintered magnets by grain boundary modificationviareduction-diffusion process

The interface between the Nd2Fe14B particles and the grain boundary surrounding them in Nd-Fe-B sintered magnets was modified by diffusion Dy metal selectively through the grain boundary involving the reduction of Dy2O3 or DyF3 with CaH2 and the coercivity of them was effectively enhanced from 0.98 MA/m to 1.42 MA/m with keeping the high value of remanence. The resultant coercivity was higher than that of the magnets modified with Dy2O3 (HcJ = 1.10 MA/m) and DyF3 (HcJ = 1.24 MA/m) without using any reductant such as CaH2, respectively.