Ultrahigh coercivity in ternary Tb-Fe-B melt-spun ribbons

Abstract

The structure and magnetic properties were studied for ternary Tb-Fe-B melt-spun ribbons with nominal composition of Tb14Fe86–xBx (x = 5.2–6.8). Effect of boron content and melt-spun wheel speed on the coercivity of the ribbons was investigated. With the increase of boron content, the coercivity of the Tb-Fe-B ribbons increases first, and then decreases. XRD results show that the impurities of TbFe2 phase and FeB phase exist in low boron content and high boron content ribbons, respectively, resulting in the coercivity degradation of the ribbons. For the Tb14Fe79.6B6.4 ribbons, the wheel speed plays an important role in their magnetic properties. As the wheel speed increases from 5 to 25 m/s, the saturation magnetization and the remanence of the ribbons drop monotonically, while the coercivity increases first, peaks at 77.4 kOe, and then decreases. Further SEM observation indicates that the microstructure of the optimal ribbons was composed of fine and uniform crystal grains, which was responsible for the ultrahigh intrinsic coercivity of the ribbons.