Coercivity temperature dependence of Sm^sub 2^Co^sub 17^-type sintered magnets with different cell and cell boundary microchemistry

• Published in: Journal of magnetism and magnetic materials Vol. 452; p. 272
• Main Authors: Yu, Nengjun, Zhu, Minggang, Song, Liwei, Fang, Yikun, Song, KuiKui, Wang, Qiang, Li, Wei
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier BV 15.04.2018
• Subjects: Coercivity; Copper; Energy measurement; High temperature; Iron; Magnetism; Magnets; Microchemistry; Powder metallurgy; Sintering; Sintering (powder metallurgy); Temperature; Temperature dependence; Transmission electron microscopy
• ISSN: 0304-8853; 1873-4766

High maximum energy product ((BH)max) Sm(CobalFe0.18Cu0.07Zr0.03)7.7 magnet (type-A) and high temperature Sm(CobalFe0.1Cu0.09Zr0.03)7.2 magnet (type-B) were prepared by a traditional powder metallurgical technology. A record (BH)max of 98.7 kJ/m3 with a coercivity (Hcj) of 501.5 kA/m at 773 K was achieved for the type-B magnet, which is much higher than that of type-A magnet (63.7 kJ/m3). The microstructures of the magnets were revealed by high-resolution transmission electron microscope. The average cell size of the type-A and B magnet are 110 nm and 90 nm, respectively. Moreover, the type-B magnet shows a wider cell boundary than the type-A magnet. Additionally, the element distribution of the cell/cell boundary interfaces was measured by energy-dispersive spectroscopy. The cell phase of the type-A magnet contains a higher Fe content as about 17 at%, comparing with that of the type-B magnet (~8.9 at%). On the other hand, the Cu content of the cell boundary phase is 18 at% almost twice higher than the type-B magnet (8.6 at%). Theoretical Hcj temperature dependence of these two kinds of magnets indicates that the lower Cu content in the cell boundary phase and the appropriate Fe content in the cell phase are the key factors for the high Hcj for the type-B magnet at elevated temperature.