High coercive Zn-bonded Sm-Fe-N magnets prepared using fine Zn particles with low oxygen content

To improve the coercivity of Zn-bonded Sm-Fe-N magnets, fine Zn particles with low oxygen content were fabricated by the hydrogen plasma-metal reaction (HPMR), and Zn-bonded Sm-Fe-N magnets were prepared using the Zn particles. The primary and secondary average Zn particle sizes were 0.23 and 0.93 mu m, respectively, and the oxygen content was 0.068 wt%. The oxygen content in the Zn-bonded Sm-Fe-N magnets prepared using the Zn particles also decreased, and the coercivity and energy products of the 15 wt% Zn-bonded Sm-Fe-N magnets were 2.66 MA.m(-1) and 53.1 kJ.m(-3), respectively, at room temperature. The 10 wt% Zn-bonded Sm-Fe-N magnet was also a high coercivity value of 2.41 MA.m(-1), and the energy product was 56.1 kJ.m(-3). The coercivity strongly depended on the oxygen content rather than the particle size of Zn, and decreasing the oxygen content in the starting material improved the magnetic properties of Zn-bonded Sm-Fe-N magnets. The coercivity of the 15 wt% Zn magnet measured at 180 and 200 degrees C was 1.23 and 1.10 MA.m(-1), respectively, and the temperature coefficient of coercivity was -0.32%.degrees C-1. (C) 2017 Elsevier B.V. All rights reserved.