Abstract
? 2022 Elsevier B.V.Effective grain boundary (GB) reconstruction process has been proposed by introducing Pr-Fe-Al-Ga intergranular additive in the B-lean Nd-La-Ce-Fe-B multi main phase (MMP) magnets. A coercivity of ~2.0 T was yielded in the Nd-Fe-B sintered magnet with 24 wt% Nd substituted by La-Ce. Detailed structural analysis revealed that the RE6Fe13(Ga, Al)1 phase was apparently formed in the triple junction area, triggered by the conducive intergranular composition environment provided by the B-lean composition and the Pr-Fe-Al-Ga addition. Simultaneously, continuous nonferromagnetic GB phases were generated to decouple the intergranular exchange, accompanied by the suppressed fraction of REFe2 and REOx phases. Elemental distribution analysis demonstrated that Pr preferred to enter La/Ce-rich grains to form a Pr-rich shell that enhanced the magnetocrystalline anisotropy field of La/Ce-rich grain surface. Overall, the Pr-rich magnetic hardening shells and the reconstruction GB structure jointly gave rise to the restrained reversion of magnetic domains, thus an extraordinary coercivity was achieved in the Nd-La-Ce-Fe-B magnet. These phenomena may provide a new insight for the development of high-figure-of-merit Nd-La-Ce-Fe-B permanent magnets.
NSTL
Elsevier