Optimization of the microstructure and phase composition of high Ce-content sintered magnets by intergranular addition of Gd-Cu alloy

Compared to introducing Nd70Cu30 (at%) alloys, the addition of Gd70Cu30 exhibited a better enhancement effect, and both the best coercivity of 9.38 kOe and magnetic energy product of 29.72 MGOe were simultaneously obtained when the Gd70Cu30 addition amount reached 4 wt% in the Nd-Ce-Fe-B magnet with Ce accounting for more than 14.16 wt% of the entire magnet. The further microstructural analyses showed that the higher coercivity when adding Gd70Cu30 alloy was mainly attributed to the continuous thin-walled grain boundary phases and the typical core-shell structure with a Ce-rich core and Gd/Nd-rich shell. Meanwhile, the unfavorable REFe2type phases had been greatly suppressed and the ratio of Ce3+ ions to Ce4+ ions had been promoted, which was generally beneficial for the improvement of magnetic properties. This work provides further insights into preparing sintered magnets with high Ce-content and high-performance.