Synthesis of ultra-high coercivity Sm2Fe17N3 powder by homogeneous reduction-diffusion with rotary furnace

• Published in: Journal of alloys and compounds Vol. 960; p. 170726
• Main Authors: Okada, Shusuke, Node, Eri, Takagi, Kenta, Hashimoto, Ryuji
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.10.2023
• Subjects: Permanent magnet; Reduction-diffusion; Sm-Fe-N; Sm2Fe17N3; Reduction-diffusion; Sm2Fe17N3; Sm-Fe-N; Permanent magnet
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2023.170726

In a reduction-diffusion (R-D) process using Ca, the uneven distribution of Ca in the reaction vessel was found to have a significant effect on the size uniformity of the Sm2Fe17 particles. It was considered that lumps of Sm-Ca-Fe formed due to the uneven distribution of Ca, and coarse Sm2Fe17 particles formed in the lumps. The R-D process using a rotary furnace was developed to solve the problem of uneven distribution of Ca in the R-D reaction, and drastically reduced the formation of Sm-Ca-Fe lumps and reduced the number of coarse Sm2Fe17 particles. As a result, Sm2Fe17N3 powders with even higher coercivity could be obtained by the R-D process. In particular, an ultra-high coercivity of over 30 kOe was achieved by reducing the average particle size to 0.5 µm or less. The highest coercivity in this study was 31.7 kOe, which is the highest value ever achieved with a Sm2Fe17N3 single-crystalline powder. The coercivity coefficient β of the synthesized powder from 303 K to 493 K was − 0.36 %/K, and the powder maintained coercivity of more than 10 kOe at 473 K. •In a reduction-diffusion (R-D) process using Ca, the uneven distribution of Ca in the reaction vessel was found to have a significant effect on the size uniformity of the Sm2Fe17 particles.•The R-D process using a rotary furnace was developed to solve the problem of uneven distribution of Ca in the R-D reaction, and drastically reduced the number of coarse Sm2Fe17 particles.•An ultra-high coercivity Sm2Fe17N3 powder of over 30 kOe was achieved by reducing the average particle size to 0.5 µm or less.•The coercivity coefficient β of the synthesized powder from 303 K to 493 K was − 0.36 %/K, and the powder maintained coercivity of more than 10 kOe at 473 K.