Novel powder processing technologies for production of rare-earth permanent magnets

Post-neodymium magnets that possess high heat resistance, coercivity, and (BH) are desired for future-generation motors. However, the candidate materials for post-neodymium magnets such as Sm₂Fe₁₇N₃ and metastable magnetic alloys have certain process-related problems: low sinterability due to thermal decomposition at elevated temperatures, deterioration of coercivity during sintering, and the poor coercivity of the raw powder. Various developments in powder processing are underway with the aim of overcoming these problems. So far, the development of advanced powder metallurgy techniques has achieved Sm₂Fe₁₇N₃ anisotropic sintered magnets without coercivity deterioration, and advances in chemical powder synthesis techniques have been successful in producing Sm₂Fe₁₇N₃ fine powders with huge coercivity. The challenge of a new powder process is expected to open the way to realizing post-neodymium magnets.