Controlling grain growth to achieve improved magnetic properties of NdCeFeB magnets via grain boundary diffusion

The abnormal growth of grains near the surface of NdCeFeB magnets reduces the number of grain boundaries, and meanwhile, the formation of REFe2 phase also hinders the diffusion of rare earth elements, both of which limit the enhancement of magnetic properties. This poses a certain challenge for the preparation of high Ce content NdCeFeB magnets. In this work, it is found that the TbPrNdAl diffusion source can suppress the mutual diffusion between Ce in the main phase and rare earth elements in the diffusion source, thereby restraining the abnormal growth of grains and inhibiting the formation of REFe2 phase. Eventually, a more uniform core-shell structure and thin and continuous RE-rich phase are formed. The coercivity of 1389 kA/m and magnetic energy product of 289 kJ/m3 can be obtained without reducing the remanence, which are 612 kA/m and 30 kJ/m3 higher than those of the initial magnet, respectively. This diffusion source can greatly promote the development of NdCeFeB magnets with high Ce content.