Coercivity Improvement in Ce-Containing (Nd,Pr)-Fe-B-Based Sintered Magnets by Application of the 2-Powder Method

The 2-powder method is an effective strategy for enhancing the utilization efficiency of rare earth elements in Nd-Fe-B-based magnets. It involves blending a main powder (MP) with a finer-sized powder characterized by a higher anisotropy field (termed anisotropy powder, AP), producing magnets with core-shell structures. This method overcomes the limitations of the grain boundary diffusion process on magnet dimensions and avoids processing costs associated with additional coating and heating. Herein, the 2-powder method is applied to counteract coercivity and remanence loss in Ce-containing (Nd,Pr)-Fe-B magnets, achieving sustainable gap magnets with reduced criticality. Two types of anisotropy powders: Nd2Fe14B-based and (Nd,Pr,Dy)2Fe14B-based, are each blended with the (Ce,Nd,Pr)2Fe14B-based MP in a 3:7 weight ratio. The MP has a mean particle size of ≈4 μm and APs of around 2.5 μm. Compared to the magnet produced from the MP alone, incorporating Nd-enriched and Dy-enriched APs increased coercivity from 750 to 931 and 1362 kA m-1, respectively. The significant improvements are attributable to the formation of core-shell structures, where Nd and Dy are selectively enriched in the shell region of RE2Fe14B grains. These distribution trends underscore the efficient rare earth element utilization realized through the 2-powder method.