Modified Process for High-Performance Anisotropic Sm2Fe17N3 Magnet Powder

The magnetic properties of an anisotropic Sm2Fe17N3 magnet powder were improved by enhancement of nitrogenation homogeneity. We made the Sm2Fe17 parent material powder by a reduction-diffusion method which contains a reduction-diffusion heat treatment and a subsequent wet process for removal of a CaO by-product. In the present study, as the modified process for the magnet powder, the nitrogenation heat treatment was done between the reduction-diffusion heat treatment and the wet process, though the nitrogenation was normally done after the wet process. The surface of the Sm2Fe17 powder before the wet process is rather clean than the surface after the wet process. It was found that the modified process seemed to promote the nitrogenation and decreased the number of Sm2Fe17N3 particles with unnitrogenated phase. The magnetic properties of the magnet powder through this process reached Br = 1.46 T, Hc = 874 kA/m and (BH)max = 353 kJ/m without demagnetizing field correction and (BH)max = 371 kJ/m with the correction assuming the density 7.67 Mg/m.