Effect of Rare-Earth Dopant on Coercivity of Hot-Pressed Nd–Fe–B Magnet Doped With RF3

Abstract

An RF3 (R = La, Ce, Pr, Nd, and Dy)-doped Nd13.6Fe73.6Co6.6Ga0.6B5.6 hot-pressed magnet was prepared using melt-spun flakes. The substitution of Nd in Nd–Fe–B flakes by rare-earth dopant in the hot-pressed magnets doped with various RF3 and its effect on coercivity were investigated. In the RF3-doped Nd13.6Fe73.6Co6.6Ga0.6B5.6 magnet hot pressed at the modest temperature (735 °C), the dopants Ce, Pr, Nd, and Dy actively substituted Nd in the region near the flake surface to form the thin shell in the flake. RF3 (R = Dy, Nd, and Pr) doping achieved significant coercivity enhancement in the hot-pressed magnet, and it was attributed to the enhanced anisotropy field of the Nd2Fe14B-type grains (for Dy and Pr doping) and grain boundary restructuring (for Nd doping) in the shell. The most profound coercivity enhancement as high as 5 kOe was achieved in the DyF3-doped magnet. Doping with the light rare-earth elements using RF3 (R = La and Ce) led to poor coercivity enhancement with respect to the RF3 (R = Dy, Nd, and Pr) doping.