High coercivity Pr2Fe14B/α-Fe nanocomposite permanent magnets with Zr addition

The ingots with nominal composition Pr 9.5 Fe 84 - x B 6.4 P 0.1 Zr x ( x = 0, 1, 2, 3) were prepared by an electric arc furnace under purified argon atmosphere. The ribbons were obtained by melt spinning at a wheel speed of 16–33 m·s −1 . X-ray diffraction (XRD) results show that P addition decreases crystallinity of hard phase, but further Zr addition increases the amorphous-forming ability of soft phase. The intrinsic coercivity largely increases from 502 (Zr-free) to 945 kA·m −1 (2 at% Zr), which is among the highest value reported so far in this poor rare earth nanocomposite magnets. The hysteresis loops of the alloys with addition of 1 at% and 2 at% Zr show good squareness with single-phase characteristic, indicating well exchange coupling between hard and soft magnetic grains. Transmission electron microscope (TEM) results reveal small grain size and uniformity in the microstructure in the Zr-added samples, which is the reason for high coercivity.