[15P-T16-05] Microstructure and Magnetic Properties of NdFeB Sintered Magnets with Nd-Based Alloy Layer Using PVD Process
キーワード：NdFeB magnet, Grain boundary diffusion process, PVD coating, Nd-based alloy layer, Magnetic property
Grain-boundary diffusion treatment has been purposed as a heavy rare-earth (HRE) element saving method, where HRE atoms are allowed to diffuse from the surface of NdFeB sintered magnets to its interior through grain boundaries upon heating. Since the magnet used for this treatment is almost fully dense, HRE atoms have the problem to diffuse into the magnet. Therefore, the low diffusion effect of heavy rare earth elements causes the limitation of the thickness of higher performance NdFeB sintered magnet. The coercivity of NdFeB sintered magnets is currently achieved at only 40% of the theoretical value. To enhance coercivity, methods such as reducing the grain size of NdFeB sintered magnets and uniformly coating the grain boundaries with oxides to suppress the formation of reverse domains have been researched.
In this study, physical vapor deposition (PVD) was performed to uniformly coated NdFeB magnetic powder with Nd-based alloy. Deposition time and voltage were optimized for thickness control of the coated layer thickness. Furthermore, the effect of sintering conditions were investigated to control the diffusion behavior of coated Nd-based alloy layer, and the correlation between the distribution of Nd layer and the magnetic properties was estimated.
In this study, physical vapor deposition (PVD) was performed to uniformly coated NdFeB magnetic powder with Nd-based alloy. Deposition time and voltage were optimized for thickness control of the coated layer thickness. Furthermore, the effect of sintering conditions were investigated to control the diffusion behavior of coated Nd-based alloy layer, and the correlation between the distribution of Nd layer and the magnetic properties was estimated.