Effects of DyHx and Dy2O3 powder addition on magnetic and microstructural properties of Nd-Fe-B sintered magnets

The magnetic and microstructural properties of (Nd27.68Dy4.89)-Febal.B1.0M2.4 (wt. %, M = Cu, Al, Co, and Nb) sintered magnets doped with Dy2O3 and DyHx powders were studied. The coercivity of the DyHx-doped magnet improved, with no change in the remanence. Well-developed core-shell microstructures were seen in the DyHx-doped magnet, as compared to the case of the Dy2O3-doped magnet. Diffusion of Dy was enhanced in the DyHx-doped magnet, probably because dissolution of hydrogen in Nd2Fe14B increased the lattice parameter. The (00L) grain alignment in the DyHx-doped magnet was also improved.