Synthesis of Sm2Fe17N3 powder having a new level of high coercivity by preventing decrease of coercivity in washing step of reduction-diffusion process

Abstract

Synthesis of Sm2Fe17N3 powder by a reduction-diffusion technique requires a washing process to remove CaO and Ca residues, but it is typically associated with a decrease of coercivity. Synchrotron radiation X-ray diffraction study revealed forming of a SmFe5 poor hard magnetic phase in a water washing treatment. Cross-sectional electron microscopic analysis of particles revealed an acetic acid washing treatment to dissolve the impurity phases accompanied surface damages on Sm2Fe17N3 particles. A new washing process to avoid forming of the factors which decrease coercivity was examined, and Sm2Fe17N3 powders having about 20% higher coercivity than that in the previous reports, achieving up to 28.1 kOe, were successfully demonstrated.