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

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.