Journal Article

FZJ-2021-02611

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Microstructural insights into the coercivity enhancement of grain-boundary-diffusion-processed Tb-treated Nd-Fe-B sintered magnets beyond the core-shell formation mechanism

Soderžnik, K. Ž. (Corresponding author) ; Rožman, K. Ž. ; Komelj, M. ; Kovács, A.FZJ* ; Diehle, P. ; Denneulin, T.FZJ* ; Savenko, A. ; Soderžnik, M. ; Kobe, S. ; Dunin-Borkowski, R. E.FZJ* ; Mayer, J.FZJ* ; Markoli, B. ; Šturm, S.

2021
Elsevier Lausanne

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Please use a persistent id in citations: http://hdl.handle.net/2128/28069  doi:10.1016/j.jallcom.2021.158915

Abstract: We propose a dominant core-shell formation mechanism for grain-boundary-diffusion-processed (GBDP), Tb-treated, Nd2Fe14B sintered magnets. A depth-sensitive analysis of Tb-treated samples, relative to a non-GBDP Nd2Fe14B magnet, showed a 30% increase of the coercivity in the central part of the magnet. A structure-chemistry-magnetic-property analysis revealed the dominant GBDP mechanism. On the surface of the Tb-treated magnet, the Tb is released from the starting precursor following a cascade of chemical reactions between the Tb oxide and the Nd and/or the Nd-Fe-B. The released Tb diffuses along the grain boundaries, forming a core-shell structure. The calculated optimum concentration for a 30% increase in the coercivity was 50 ppm of Tb. Off-axis electron-holography measurements were used to quantitatively map the characteristic magnetic states of the samples, confirming a different magnetic domain structure in the shell than in the core. The magnetic induction in the core was found to be 26% higher than that of the shell, which has a lower magnetic saturation due to the presence of Tb. The results show that the measured increase in the coercivity is due to a structural effect, and not the magnetic contribution of the Tb. Our results pave the way towards grain-boundary-engineering studies that can be used to increase the coercivity of Nd-Fe-B magnets for e-mobility and eco-power applications.

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Contributing Institute(s):

1. Physik Nanoskaliger Systeme (ER-C-1)

Research Program(s):

1. 535 - Materials Information Discovery (POF4-535) (POF4-535)
2. ESTEEM3 - Enabling Science and Technology through European Electron Microscopy (823717) (823717)
3. 3D MAGiC - Three-dimensional magnetization textures: Discovery and control on the nanoscale (856538) (856538)
4. DFG project 405553726 - TRR 270: Hysterese-Design magnetischer Materialien für effiziente Energieumwandlung (405553726) (405553726)

Appears in the scientific report 2021

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Database coverage:
; ; ; Clarivate Analytics Master Journal List ; Current Contents - Physical, Chemical and Earth Sciences ; Ebsco Academic Search ; Essential Science Indicators ; IF < 5 ; JCR ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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