Preparation of submicron-sized Sm2Fe17N3 fine powder with high coercivity by reduction-diffusion process

Submicron-sized Sm 2 Fe 17 N 3 powders having high coercivity were prepared by a newly-developed synthesis procedure for submicron-sized Sm 2 Fe 17 powders and nitridation process with a proper post-process for the powders. It was revealed that the washing step, which is performed to remove excess Ca, supplied hydrogen into the Sm 2 Fe 17 N 3 crystal structure, and elongation of the crystal structure along the c-axis by the supplied hydrogen reduced coercivity. This phenomenon was observed clearly in powder with a smaller size and good dispersity. When the powders were subjected to dehydrogenation treatment, they showed high coercivity, as expected from the particle size, and coercivity of 24.7 kOe was achieved with the 0.5 μm powder. The fact that the intrinsic good thermal stability of Sm 2 Fe 17 N 3 is maintained at the submicron-scale was also confirmed. In addition, the obtained powder exhibited a high maximum energy product after disintegration treatment under appropriate conditions. This study demonstrated the high potential of Sm 2 Fe 17 N 3 for surpassing the performance of Nd Fe B magnets under hot environments.