Simultaneous application of Dy-X (X = F or H) powder doping and dip-coating processes to Nd-Fe-B sintered magnets

Tae Hoon Kim; Seong Rae Lee; Hyo Jun Kim; Min Woo Lee; Tae Suk Jang

doi:10.1016/j.actamat.2015.04.019

Simultaneous application of Dy-X (X = F or H) powder doping and dip-coating processes to Nd-Fe-B sintered magnets

Tae Hoon Kim, Seong Rae Lee, Hyo Jun Kim, Min Woo Lee, Tae Suk Jang

Department of Materials Science and Engineering

Research output: Contribution to journal › Article › peer-review

87 Citations (Scopus)

Abstract

We investigated the microstructural and magnetic property changes of Nd-Fe-B sintered magnets with the application of simultaneous processing via powder doping and dip-coating, using DyF₃ and/or DyH₂. The simultaneous use of DyF₃ powder doping and DyH₂ dip-coating has a synergistic effect of improving the magnet's coercivity (H_c) while minimizing the reduction of remanence (B_r). DyF₃ powder doping suppresses the formation of the rare-earth segregated oxide phase (RE-rich phase, Dy-Nd-O or Nd-O), dramatically improving the grain boundary diffusion depth of Dy (from 250 to 600 μm) during the grain boundary diffusion process (GBDP). The RE-rich phase in Nd-Fe-B magnets is a major obstacle for the grain boundary diffusion of Dy because of the high surface energy of the RE-rich phase and the consumption by the non-stoichiometric RE-rich phase of diffused Dy to form a stoichiometric (Nd, Dy)₂O₃ phase. The slight reduction of the relative density of the as-sintered DyF₃-doped magnet (from 98.1% to 97.5%) may have also helped to improve the grain boundary diffusion depth of Dy during the GBDP when the magnets were dip-coated with DyH₂.

Original language	English
Pages (from-to)	95-104
Number of pages	10
Journal	Acta Materialia
Volume	93
DOIs	https://doi.org/10.1016/j.actamat.2015.04.019
Publication status	Published - 2015 Jul 1

Bibliographical note

Funding Information:
This research was supported by the Technology Innovation Program funded by the Ministry of Knowledge Economy (MKE, South Korea) (No. 10043780 ), Republic of Korea.

Publisher Copyright:
© 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Keywords

Core-shell microstructure
Grain boundary diffusion depth of Dy
Grain boundary diffusion process
Nd-Fe-B sintered magnet
Powder doping process

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Ceramics and Composites
Polymers and Plastics
Metals and Alloys

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10.1016/j.actamat.2015.04.019

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title = "Simultaneous application of Dy-X (X = F or H) powder doping and dip-coating processes to Nd-Fe-B sintered magnets",

abstract = "We investigated the microstructural and magnetic property changes of Nd-Fe-B sintered magnets with the application of simultaneous processing via powder doping and dip-coating, using DyF3 and/or DyH2. The simultaneous use of DyF3 powder doping and DyH2 dip-coating has a synergistic effect of improving the magnet's coercivity (Hc) while minimizing the reduction of remanence (Br). DyF3 powder doping suppresses the formation of the rare-earth segregated oxide phase (RE-rich phase, Dy-Nd-O or Nd-O), dramatically improving the grain boundary diffusion depth of Dy (from 250 to 600 μm) during the grain boundary diffusion process (GBDP). The RE-rich phase in Nd-Fe-B magnets is a major obstacle for the grain boundary diffusion of Dy because of the high surface energy of the RE-rich phase and the consumption by the non-stoichiometric RE-rich phase of diffused Dy to form a stoichiometric (Nd, Dy)2O3 phase. The slight reduction of the relative density of the as-sintered DyF3-doped magnet (from 98.1% to 97.5%) may have also helped to improve the grain boundary diffusion depth of Dy during the GBDP when the magnets were dip-coated with DyH2.",

keywords = "Core-shell microstructure, Grain boundary diffusion depth of Dy, Grain boundary diffusion process, Nd-Fe-B sintered magnet, Powder doping process",

author = "Kim, {Tae Hoon} and Lee, {Seong Rae} and Kim, {Hyo Jun} and Lee, {Min Woo} and Jang, {Tae Suk}",

note = "Funding Information: This research was supported by the Technology Innovation Program funded by the Ministry of Knowledge Economy (MKE, South Korea) (No. 10043780 ), Republic of Korea. Publisher Copyright: {\textcopyright} 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.",

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doi = "10.1016/j.actamat.2015.04.019",

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AU - Kim, Tae Hoon

AU - Lee, Seong Rae

AU - Kim, Hyo Jun

AU - Lee, Min Woo

AU - Jang, Tae Suk

N1 - Funding Information: This research was supported by the Technology Innovation Program funded by the Ministry of Knowledge Economy (MKE, South Korea) (No. 10043780 ), Republic of Korea. Publisher Copyright: © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

PY - 2015/7/1

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N2 - We investigated the microstructural and magnetic property changes of Nd-Fe-B sintered magnets with the application of simultaneous processing via powder doping and dip-coating, using DyF3 and/or DyH2. The simultaneous use of DyF3 powder doping and DyH2 dip-coating has a synergistic effect of improving the magnet's coercivity (Hc) while minimizing the reduction of remanence (Br). DyF3 powder doping suppresses the formation of the rare-earth segregated oxide phase (RE-rich phase, Dy-Nd-O or Nd-O), dramatically improving the grain boundary diffusion depth of Dy (from 250 to 600 μm) during the grain boundary diffusion process (GBDP). The RE-rich phase in Nd-Fe-B magnets is a major obstacle for the grain boundary diffusion of Dy because of the high surface energy of the RE-rich phase and the consumption by the non-stoichiometric RE-rich phase of diffused Dy to form a stoichiometric (Nd, Dy)2O3 phase. The slight reduction of the relative density of the as-sintered DyF3-doped magnet (from 98.1% to 97.5%) may have also helped to improve the grain boundary diffusion depth of Dy during the GBDP when the magnets were dip-coated with DyH2.

AB - We investigated the microstructural and magnetic property changes of Nd-Fe-B sintered magnets with the application of simultaneous processing via powder doping and dip-coating, using DyF3 and/or DyH2. The simultaneous use of DyF3 powder doping and DyH2 dip-coating has a synergistic effect of improving the magnet's coercivity (Hc) while minimizing the reduction of remanence (Br). DyF3 powder doping suppresses the formation of the rare-earth segregated oxide phase (RE-rich phase, Dy-Nd-O or Nd-O), dramatically improving the grain boundary diffusion depth of Dy (from 250 to 600 μm) during the grain boundary diffusion process (GBDP). The RE-rich phase in Nd-Fe-B magnets is a major obstacle for the grain boundary diffusion of Dy because of the high surface energy of the RE-rich phase and the consumption by the non-stoichiometric RE-rich phase of diffused Dy to form a stoichiometric (Nd, Dy)2O3 phase. The slight reduction of the relative density of the as-sintered DyF3-doped magnet (from 98.1% to 97.5%) may have also helped to improve the grain boundary diffusion depth of Dy during the GBDP when the magnets were dip-coated with DyH2.

KW - Core-shell microstructure

KW - Grain boundary diffusion depth of Dy

KW - Grain boundary diffusion process

KW - Nd-Fe-B sintered magnet

KW - Powder doping process

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Simultaneous application of Dy-X (X = F or H) powder doping and dip-coating processes to Nd-Fe-B sintered magnets

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

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