RE₂Fe₁₄C: Potential heavy-rare-earth-free permanent magnets toward high temperature applications

The reliance on heavy-rare-earth elements poses a critical challenge for the development and application of Nd-Fe-B permanent magnets, which are essential for future technologies. In this study, we propose a novel solution by designing and fabricating heavy-rare-earth-free permanent magnets based on the RE₂Fe₁₄C system, aimed at achieving high coercivity and high thermal stability for potential usage in high-temperature applications. Using first-principles calculations, we identified the distortion of trigonal prisms in the crystal structure as the key factor driving phase instability of the RE₂Fe₁₄C phase, and confirmed that B substitution can significantly enhance phase stability. Then, we validated our approach by producing high-performance Pr₂Fe₁₄(C, B) ribbons through melt spinning and heat treatment. For the optimized composition and processing, a coercivity of 1975 kA/m was achieved. Additionally, we developed a one-step hot deformation process that yielded a high-purity 2:14:1 phase with a strong c -axis texture. The resulting hot-deformed magnets exhibited magnetic properties comparable to commercial H-grade magnets, with _i H _C = 1459 kA/m, B _r = 1.17 T and ( BH )_max = 249 kJ/m³, despite the absence of heavy rare earth and typical alloying elements such as Ga, Cu, Al, and Zr. A pinning mechanism of the high coercivity of the HD magnet is also observed. Both the ribbons and bulks show significantly improved coercivity temperature coefficients compared to their commercial counterparts. This work provides valuable insights into the phase stability of the RE₂Fe₁₄C system and demonstrates its potential as low-cost and high-coercivity magnets, unlocking new possibilities for the development of advanced permanent magnets.