TY - JOUR
T1 - Microstructural changes in high-coercivity Zn-bonded Sm-Fe-N magnets
AU - Matsuura, Masashi
AU - Yamamoto, Kuniko
AU - Tezuka, Nobuki
AU - Sugimoto, Satoshi
N1 - Funding Information:
This work was partially supported by the Future Pioneering Program “Development of magnetic material technology for high-efficiency motors”, Grant Number JPNP14015, commissioned by the New Energy and Industrial Technology Development Organization (NEDO), Toyota Motor Corporation, and the Elements Strategy Initiative Center for Magnetic Materials (ESICMM), Grant Number JPMXP0112101004 , through the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.
Publisher Copyright:
© 2020 Elsevier B.V.
PY - 2020/9/15
Y1 - 2020/9/15
N2 - In this study, the relationship between the microstructural and coercivity changes of Zn-bonded Sm-Fe-N magnets was investigated. A Zn-bonded Sm-Fe-N magnet prepared using a fine Zn powder with a low O content exhibited a high coercivity of 2.7 MA m−1, whereas a Zn-free magnet displayed a low coercivity of only 0.31 MA m−1. The raw commercial Sm-Fe-N powder contained an oxidized layer at the surface of the powder with a thickness of approximately 13 nm. In the Zn-free Sm-Fe-N magnet, O diffused into interior of Sm2Fe17N3 grains to generate coarse α-Fe grains with diameters of several tens of nanometers in the oxidized layer. In the high-coercivity Zn-bonded magnet, a Zn-rich region existed at the surface of the Sm2Fe17N3 grains. In the Zn-diffused region, Fe, Zn, Sm, and O were detected via transmission electron microscopy / energy-dispersive X-ray analysis, and this region contained fine grains of Γ-FeZn, α-FeZn, and Sm-O. The non-magnetic Γ-FeZn phase served to magnetically isolate the soft magnetic α-FeZn phase from the Sm2Fe17N3 phase, resulting in the Zn-bonded Sm-Fe-N magnet with high coercivity.
AB - In this study, the relationship between the microstructural and coercivity changes of Zn-bonded Sm-Fe-N magnets was investigated. A Zn-bonded Sm-Fe-N magnet prepared using a fine Zn powder with a low O content exhibited a high coercivity of 2.7 MA m−1, whereas a Zn-free magnet displayed a low coercivity of only 0.31 MA m−1. The raw commercial Sm-Fe-N powder contained an oxidized layer at the surface of the powder with a thickness of approximately 13 nm. In the Zn-free Sm-Fe-N magnet, O diffused into interior of Sm2Fe17N3 grains to generate coarse α-Fe grains with diameters of several tens of nanometers in the oxidized layer. In the high-coercivity Zn-bonded magnet, a Zn-rich region existed at the surface of the Sm2Fe17N3 grains. In the Zn-diffused region, Fe, Zn, Sm, and O were detected via transmission electron microscopy / energy-dispersive X-ray analysis, and this region contained fine grains of Γ-FeZn, α-FeZn, and Sm-O. The non-magnetic Γ-FeZn phase served to magnetically isolate the soft magnetic α-FeZn phase from the Sm2Fe17N3 phase, resulting in the Zn-bonded Sm-Fe-N magnet with high coercivity.
KW - High coercivity
KW - Microstructure
KW - Transmission electron microscopy
KW - Zn-bonded Sm-Fe-N magnets
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U2 - 10.1016/j.jmmm.2020.166943
DO - 10.1016/j.jmmm.2020.166943
M3 - Article
AN - SCOPUS:85084117031
SN - 0304-8853
VL - 510
JO - Journal of Magnetism and Magnetic Materials
JF - Journal of Magnetism and Magnetic Materials
M1 - 166943
ER -