Magnetic properties of Dy-diffused Nd-Fe-B powder prepared by crystallization from amorphous state

摘要

The method of enhancing coercivity of isotropic Nd-Fe-B flakes using simultaneous diffusion of Dy and crystallization from the amorphous state was applied to Nd-Fe-B powders. Metal Dy coating was synthesized on amorphous Nd_(2.36)Fe_(14)B_(1.05) powders by the vapor deposition method, and the powders were crystallized by a flash annealing. Simultaneous diffusion of Dy from their surfaces using the crystallization enhanced the coercivity of isotropic Nd-Fe-B powders. The coercivity H_c increased and the remanence M_r decreased nearly linearly with the amount of Dy, and the coating of 4.5 wt.% Dy resulted in 25.3 % increase in H_c and 6.5% decrease in M_r. The decrease in M_r of the Nd-Fe-B powders is nearly the same in magnitude to that previously reported for Nd_(2.36)Fe_(14)B_(1.05) flakes, which suggests that the method of Dy diffusion using crystallization from amorphous state is applicable to Nd-Fe-B amorphous powders as well as flakes. The energy-dispersive X-ray spectroscopy revealed that Dy coating is inhomogenous, and a further enhancement in H_c is expected by improving the coating method.