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Preparation of high performance Sm-Fe-N bulk magnets with low oxygen content

The 2nd Symposium for World Leading Research Centers-Materials Science and Spintronics-, 2019, 2. 16

2019年2月16日(土)
(2019.02.16 更新)

Masashi Matsuura, Yuki Nishijima, Nobuki Tezuka, Satoshi Sugimoto (Tohoku University), Tetsuya Shoji, Noritsugu Sakuma (Toyota Notor Corp.)

Abstract

 Sm2Fe17N3 has a high saturation magnetization, a large anisotropy field, and a high Curie temperature, however,this compound cannot be sintered because of decomposition above about 600・C. To obtain high performance Sm-Fe-N bulk magnet, Zn-bonded Sm-Fe-N magnets is expected.
To obtain high performance Zn-bonded Sm-Fe-N bulk magnets, it is required to achieve following conditions;decreasing oxygen content in magnets, decreasing Zn content maintaining with well dispersibility, and increasing relative density. In this study, we adopted two processes; (i) preparing fine and low oxygen Zn powder, (ii) preparing low-oxygen Sm-Fe-N powder and applying the Arc-Plasma-Deposition (APD) for Zn deposition on the Sm-Fe-N powder (iii) Spark plasma sintering (SPS) for increasing relative density of bulk magnets.
At first, we prepared fine and low oxygen Zn power (d50=0.23・m,oxygen content=680 ppm) by the Hydrogen-Plasma-Metal-Reaction (HPMR) method. The oxygen content in the Zn-bonded Sm-Fe-N magnets prepared using the Zn powder also decreased comparing with Zn-bonded Sm-Fe-N magnets prepared using commercial Zn powder. The low oxygen Zn- bonded Sm-Fe-N magnets prepared using HPMR-Zn powder showed high coercivity of 2.66 MA/m (15 wt% Zn) and 2.41 MA/m (10 wt% Zn)[1].
Second, low-oxygen Sm-Fe-N powder was prepared by ball milling and nitriding. Then, well dispersed and lowoxygen Zn was deposited on the Sm-Fe-N powders by the APD. The APDed Sm-Fe-N/Zn composite powder was sintered by Spark plasma sintering (SPS), and 3.3 wt% Zn-bonded Sm-Fe-N magnet showed high (BH)max of 153 kJ/m3 with relatively high coercivity of 1.14 MA/m. We also prepared Zn-free Sm-Fe-N bulk magnets by SPS under low oxygen atmosphere, and we successfully obtained Zn-free Sm-Fe-N magnet that showing high (BH)max of 179 kJ/m3 [2]

[1] Masashi Matsuura, Tomoki Shiraiwa, Nobuki Tezuka, Satoshi Sugimoto, Tetsuya Shoji, Noritsugu Sakuma, Kazuaki Haga, J. Magn. Magn. Mater., 452 (2018) 243-248.
[2] Masashi Matsuura, Yuki Nishijima, Nobuki Tezuka, Satoshi Sugimoto, Tetsuya Shoji, Noritsugu Sakuma, J. Magn. Magn. Mater., 467 (2018) 64-68.


その他特記事項

謝辞「This study is partially supported by the Elemental Strategy Initiative Center for
Magnetic Materials (ESICMM) under the outsourcing project of MEXT, JAPAN.」



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構造材料元素戦略研究拠点 (京都大学)
高効率モーター用磁性材料技術研究組合
高効率モーター用 磁性材料技術研究組合