Coercivity enhancement of the sintered Nd-Ce-Fe-B magnet via grain boundary diffusion with Tb70Fe30 alloy

Commercial N45 sintered Nd-Ce-Fe-B magnets were processed by the grain boundary diffusion (GBD) with Tb and Tb70Fe30 alloys. Although the substitution of Tb (30 at.%) by Fe in the Tb70Fe30 alloy, the coercivity was still remarkably enhanced from 12.71 kOe to 22.17 kOe, nearly as well as the Tb GBD magnet. Especially, the Tb70Fe30 GBD magnet possessed a higher remanence of 13.01 kGs than that of 12.72 kGs for the Tb GBD magnet. The thickness of the Tb-rich shell was reduced in the Tb70Fe30 GBD magnet. Moreover, the antiferromagnetic RE6Fe13Cu phase was found in grain boundary in both diffused magnets, while more Fe atoms provided in the Tb70Fe30 alloy decreased the decomposition of the matrix grains due to the formation of the RE6Fe13Cu phase, thereby suppressed the remanence degradation. This work provides new prospects for the development of the Nd-Ce-Fe-B magnets processed by grain boundary diffusion.