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

• Published in: Journal of microscopy (Oxford) Vol. 236; no. 2; pp. 104 - 108
• Main Authors: WATANABE, N, UMEMOTO, H, ISHIMARU, M, ITAKURA, M, NISHIDA, M, MACHIDA, K
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.11.2009
• Subjects: Amorphous; energy dispersive X-ray spectroscopy (EDS); grain boundary; terbium; transmission electron microscopy (TEM); wetting-layer
• ISSN: 0022-2720; 1365-2818
• DOI: 10.1111/j.1365-2818.2009.03231.x

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 Nd₂Fe₁₄B grain. The results suggest that the wrapped structure prevents the nucleation of magnetic reversed domains and then improves significantly the coercivity of the magnet.