Overcoming Refractory REFe <sub>2</sub> Phase Bottleneck in High‐Ce Nd–Ce–Fe–B Magnets via Praseodymium‐Induced Phase Transformation: Enabling Liquid‐Phase Grain Boundary Diffusion of Dysprosium
Qing Feng, Dong Huang, Lizhong Zhao, Jinkui Fan, Liang Jin, Yu Pan, Yuan Hong, Xiaolian Liu, Anjian Pan, Haoyang Jia, Shuai Liu, Zhongwu Liu, Xuefeng Zhang
Abstract
Abstract High‐cerium Nd–Ce–Fe–B magnets suffer from severe coercivity degradation, primarily stemming from the poor intrinsic magnetic properties of the Ce 2 Fe 14 B phase. Although dysprosium (Dy) grain boundary diffusion (GBD) has emerged as a critical strategy for coercivity enhancement, its effectiveness is significantly hindered by the presence of refractory rare‐earth REFe 2 phases. To address this bottleneck, the Dy x Pr 80−x Al 10 Ga 10 (x = 0, 20, 40, 80 at.%) diffusion sources are designed, where Pr (praseodymium), Al, and Ga synergistically transform REFe 2 into low‐melting‐point PrGa‐rich phases, thereby constructing efficient liquid‐phase diffusion pathways for Dy. First‐principles calculations indicate that the positive formation energy of Pr doped CeFe 2 phase destabilizes the (Pr, Ce)Fe 2 phase, facilitating the liquid‐phase transformation below the GBD temperature (930 °C). Correlative microstructural analyses demonstrate that these liquid‐phase pathways enable a higher Dy diffusion coefficient and more uniform core–shell structures, effectively suppressing reversed magnetic domains expansion and enhancing coercivity. For magnets with 26, 39, 45, and 61 wt.% Ce‐substitution, the robust coercivity increments of 7.0, 5.4, 5.5, and 3.9 kOe are achieved, respectively, using only ≈0.39 wt.% Dy. This strategy overcomes the long‐standing barrier of REFe 2 phases in GBD and provides a scalable route for producing Ce‐rich Nd–Ce–Fe–B magnets with high performance.