Microstructure and magnetic properties of SmCo 5 sintered magnets
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Rare Met. https://doi.org/10.1007/s12598-018-01198-8
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Microstructure and magnetic properties of SmCo5 sintered magnets Dong-Tao Zhang, Rong-Chun Zhu, Ming Yue*
, Wei-Qiang Liu
Received: 18 December 2017 / Revised: 14 March 2018 / Accepted: 14 December 2018 Ó The Nonferrous Metals Society of China and Springer-Verlag GmbH Germany, part of Springer Nature 2019
Abstract SmCo5 sintered magnets with good thermal stability are mainly used in high-temperature field. In this study, two types of SmCoz powders with different nominal z values were mixed and synthesized into SmCo5 magnets by the traditional powder metallurgy method. The magnetic properties of the SmCo5 sintered magnet are maximum energy product of (BH)max = 172.29 kJm-3, remanence of Br = 7.47 9 105 Am-1 and coercivity of Hci = 2.42 T. The results show that there are three coexisting phases in the magnet, which are SmCo5 phase, Sm2Co7 phase and Sm2O3 phase. The microstructural observation indicates that the average grain size in the magnet is about 8 lm, and the high coercivity of this magnet is attributed to these fine grains. X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) results indicate that the magnet has a well-aligned (00l) orientation texture. Keywords SmCo5; Sintered magnets; Magnetic properties
1 Introduction As the first generation of rare earth permanent magnets [1], the SmCo5 magnet with high Curie temperature and high coercivity is widely used in traveling wave tube, particle accelerator, aerospace system gyroscope, etc. [2–7]. The Curie temperature (727 °C) and saturation magnetization of SmCo5 magnet are lower than those of 2:17
D.-T. Zhang, R.-C. Zhu, M. Yue*, W.-Q. Liu College of Materials Science and Engineering, Key Laboratory of Advanced Functional Materials, Ministry of Education of China, Beijing University of Technology, Beijing 100124, China e-mail: [email protected]
SmCo magnet, but its magnetocrystalline anisotropy field is 40 T at room temperature, which is much higher than that of 2:17 SmCo and other SmCo compounds [8–13]. Compared with 2:17 SmCo magnet, the synthesis process of SmCo5 magnet is simpler, so the cost of production is lower. In addition, SmCo5 magnet has better corrosion resistance and temperature stability than NdFeB magnet [14–16]. Up to now, RCo5 (R = Sm, Pr, La, Gd, Y) and R(Co, M)5 magnets have been studied [4, 17, 18]. Magnetic energy product of SmCo5 magnet reaches 190.99 kJm-3 in 1972 [19], and magnetic energy product of PrCo5 magnet is 208.49 kJm-3 by 1984 [20]. Moreover, electron backscattered diffraction (EBSD) study of SmCo5 magnets was also involved [21]. But the relationship between magnetic properties and microstructure is still not clear. Among crystallographic texture measurement methods, the EBSD technique has the capabilities to measure the textures of the grains [14, 22, 23]. The preferential distribution of the grain orientation usually represents the orientation texture of crystal. The excellent orientation texture of c-axis usually
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