Microstructure analysis of Nd‐Fe‐B sintered magnets improved by Tb‐metal vapour sorption

Abstract

Behaviours of constituent elements in the Nd-Fe-B sintered magnets improved by Tb-metal vapour sorption have been investigated by using an analytical transmission microscopy. It was found that a triple junction of the grain boundaries consists of fine Nd-O crystalline and amorphous phase. The energy dispersive X-ray spectroscopy (EDS) analysis showed that the amorphous phase mainly consists of Co, Nd and Tb. The Tb-treatment causes the formation of the amorphous Co-Nd(Tb) wetting-layer phase which wraps each Nd(2)Fe(14)B grain. The results suggest that the wrapped structure prevents the nucleation of magnetic reversed domains and then improves significantly the coercivity of the magnet.