A Promising MM–Fe–Al–Ga–B Permanent Material with Substantially Boosted Magnetic Performance

Exploiting the potential of mischmetal (MM, La-Ce-Pr-Nd mixture containing ≈80 wt% La-Ce) based MM-Fe-B permanent material as an advantageous alternative for the current Nd-Fe-B is intriguing, whereas remains an arduous quest due to the drastically deteriorated magnetic performance. Herein, a facile two-step strategy is proposed that Al-doping towards high maximum energy product (BH)_max with the subsequential grain boundary diffusion processing (GBDP) toward high coercivity H_cj, i.e., a representative 0.7 wt% Al doping and Nd/Pr-based GBDP yields the record-high H_cj = 10.14 kOe and (BH)_max = 28.02 MGOe for the MM-Fe-Al-Ga-B sintered magnets. Appropriate Al-doping plays a pivotal role in accelerating the La/Ce segregation in the LaCe-rich RE-(Al, Ga), La-rich RE₆(Fe, Al, Ga)₁₄, and Ce-rich REFe₂ intergranular phases, resulting in enhanced intrinsic and extrinsic magnetism. The following Nd/Pr-based GBDP generates large quantities of RE₆(Fe, Al, Ga)₁₄ phase in triple junctions and grain boundaries, together with continuous Nd/Pr-rich magnetically hardening shell, finally harvesting the substantially boosted magnetic performance. This demonstration marks a clear picture of the two-step strategy towards fully utilizing the abundant MM resources, and overcoming the long-standing difficulty of applicable MM-Fe-B permanent material for industrialization.