Comparison of (Pr, Nd)H-x grain boundary restructuring and diffusion on the magnetic properties of Nd-La-Ce-Fe-B sintered magnet

摘要

Exploiting high-performance 2:14:1-type permanent magnet at high La-Ce substitution level remains a bottleneck concern due to the severe magnetic dilution from inferior intrinsic magnetism and microstructural deterioration. In present work, to promote the La-Ce application, (Pr, Nd)H-x is introduced into LaCe-40 sintered magnet (La-Ce/TRE = 40 wt%, TRE: total rare earth) through two approaches, grain boundary restructuring (GBR) and grain boundary diffusion process (GBDP). Results show that (Pr, Nd)H-x GBR leads to a twofold coercivity by optimizing the distribution of GB phase and forming a Pr/Nd-rich magnetically hardening shell. However, the remanence is lowered drastically due to massive formation of REFe2 phase during high-temperature sintering. Comparably, (Pr, Nd)H-x GBDP magnet with an identical average composition to GBR one yields a nearly threefold coercivity without sacrificing the remanence, ascribing to the formation of more continuous RE-rich GB layer and thicker Pr/Nd-rich shell near the surface region. Above comparative study highlights the crucial role of surface magnetic isolation in enhancing the coercivity of Nd-La-Ce-Fe-B sintered magnet, and delights the prospect of abundant La-Ce for industrial application. (C) 2021 Elsevier B.V. All rights reserved.