Low Melting-point Diffusion Salts of Heavy Rare-earth for Enhancing Coercivity of Grain-boundary-diffusion-processed Nd-Fe-B-type Magnet

Abstract

Effective low melting-point Dy-diffusion for grain boundary diffusion treatment for enhancing coercivity in Nd-Fe-B-type magnet was found in the DyF₃-LiF binary system. Efficacy of the low melting-point (DyF₃-LiF) diffusion source as Dy-diffusion source for enhancing coercivity in the diffusion processed Nd-Fe-B-type magnet was investigated. Speedier and more profound coercivity enhancement in the Nd-Fe-B-type magnet was achieved by grain boundary diffusion using the low melting-point (DyF₃-LiF) diffusion source with respect to solid DyF₃ single salt. Since the liquid in the (DyF₃-LiF) mixture contained plenty of Dy atoms already freed from DyF₃ and they were in better contact with magnet, speedier and profuse diffusion of Dy atoms through Nd-rich grain boundary was possible in the magnet coated with low melting-point (DyF₃-LiF) diffusion source.