Strategy for Co‐Enhancement of Remanence–Coercivity of RE‐Fe‐B Sintered Magnets with High Ce‐Content: Appropriate La Substitution

Abstract

The development of low-cost RE-Fe-B sintered magnets with large La/Ce content is of great significance for the balanced utilization of rare earth (RE) resources, but it is limited by reduced magnetic properties. In this work, the coercivity (H_cj ), remanence (B_r ), maximum energy product [(BH)_max ], and temperature stability are simultaneously enhanced for magnets with LaCe accounting for 40 wt% of the total RE. The synergistic regulation of the REFe₂ phase, Ce-valence, and grain boundaries (GBs) in RE-Fe-B sintered magnets is realized for the first time by introducing appropriate La elements. The La elements inhibit the generation of the REFe₂ phase and tend to stay in the triple junctions, promoting the segregation of the RE/Cu/Ga elements and contributing to the formation of Ce/Nd/Cu/Ga-rich continuous thicker lamellar GBs, and as a result, weakening the detrimental effect on HA caused by La element substitution and enhancing H_cj . In addition, partial La atoms entering the RE₂ Fe₁₄ B phase are beneficial for improving the B_r and temperature stability of the magnets and promoting the Ce³⁺ ion ratio, which also provides additional benefit for B_r . The findings provide an effective and feasible way to co-enhance the remanence and coercivity of RE-Fe-B sintered magnets with high Ce content.