Microstructure, phase evolution and magnetic properties of melt-spun SmCo6.8−xSnxZr0.2 (x = 0, 0.1 and 0.3) ribbons

SmCo6.8−xSnxZr0.2 (x = 0, 0.1 and 0.3) melt-spun ribbons have been produced from bulk as-cast samples by varying wheel speeds from 8 to 32 m/s. The microstructure, phase evolution and magnetic properties of as-spun ribbon samples were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM), respectively. The XRD results show that the addition of Sn to SmCo6.8Zr0.2 alloy has significant role to shift the TbCu7-structure into Sm2Co17(H) and Sm2Co17(R) -phases for the Sn content of 0.1 and 0.3, respectively. The SEM analysis reveals that the grain size of the as-spun ribbon samples is gradually refined from several microns to 600−800 nm with the increase of wheel speed from 8 to 32 m/s. A wheel speed of 24 m/s has been found to be optimal in achieving reasonably good combination of coercivity (Hc) and magnetization (Ms) values in the as-spun SmCo6.8-xSnxZr0.2 (x = 0, 0.1 and 0.3) ribbons. Maximum values of Hc of 5.1 kOe and Ms of 76.9 emu/g were achieved for the SmCo6.5Sn0.3Zr0.2 ribbons spun at 24 m/s; upon annealing at 550 °C, the Hc values of these ribbons were significantly improved (10.4 kOe) with not much destruction in the Ms value.