Breaking through the coercivity enhancement limitation of heavy rare earth-diffused Ce-rich Nd-Ce-Fe-B magnets via tailored grain boundary engineering.

Authors

Qing Feng, Shuainan Xu, Jingxian Xia, Mingpeng Kou, Liuxin Yang, Hongya Yu, Zhongwu Liu

Published in

Materials horizons. Oct 03, 2026. Epub Oct 03, 2026.

Abstract

The grain boundary diffusion (GBD) process shows advantages in enhancing coercivity and reducing the usage of heavy rare earth (HRE) elements in Nd-Fe-B magnets but faces challenges in Ce-rich Nd-Ce-Fe-B magnets. Here, we investigated the effects of the intergranular CeFe₂ phase on Dy diffusion in sintered Nd-Ce-Fe-B magnets with 13 wt% Ce. The results revealed that the intrinsically higher diffusion efficiency of Dy in the liquid phase triggers preferential Dy segregation in the RE-rich phases, resulting in non-uniform Dy-rich grain shell formation. The dissolution of Dy in the CeFe₂ phase reduces the available Dy atoms for the formation of an effective Dy-rich shell, limiting coercivity enhancement to only 217.7 kA m^-1via DyH_x GBD. A tailored grain boundary engineering (GBE) strategy was proposed to overcome this limitation. Pr-Al-Ga alloy was initially employed to substantially reduce the CeFe₂ phase content and form a RE-rich phase-dominated grain boundary structure in the magnet, enabling subsequent highly efficient DyH_x diffusion. Specifically, the Pr-Al-Ga GBE process slightly increased the coercivity by 205.6 kA m^-1, while the subsequent DyH_x diffusion led to a further substantial increase of 500.7 kA m^-1. Finally, this grain boundary engineering-assisted diffusion led to a remarkable coercivity enhancement of 706.3 kA m^-1, which is comparable or even higher than those of the DyH_x-diffused Ce-free Nd-Fe-B magnets. Importantly, validation with TbH_x diffusion suggests that the proposed strategy is potentially applicable to different HRE diffusion sources. This work not only provides a feasible approach for breaking through the coercivity enhancement limitation of Ce-rich Nd-Ce-Fe-B magnets but also elucidates the critical role of the intergranular phase structure in GBD.

PMID:
42826992
Bibliographic data and abstract were imported from PubMed on 03 Oct 2026.

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