Fabrication of High-performance Sm–Fe–N isotropic bulk magnets by a combination of High-pressure compaction and current sintering

Abstract

TbCu7-type Sm–Fe–N coarse powders in the flake form were consolidated without a bonding medium using a low-thermal-load process of current sintering combined with high-pressure compression. When compacted at 1.2GPa, the relative density of the powder was increased by 80% with close stacking of the flake particles. Although the subsequent current heating was only briefly performed at a low temperature of 400°C to avoid decomposition, the compact was consolidated into a rigid bulk in which the particles were bonded at the atomic level. Finally, by using cyclic compaction, this process produced bulk magnets with a density of 92% that exhibited the highest maximum energy product (BH)max of 16.2MGOe, which surpasses that of conventional isotropic Sm–Fe–N bond magnets.