Origin of the coercivity difference in sintered Nd-Fe-B magnets by grain boundary diffusion process using TbH3 nanoparticles and TbF3 microparticles

Abstract

Abstract Nd-Fe-B sintered magnets with different thicknesses of up to 10\u202fmm were fabricated by combining TbH3 nanoparticles as diffusion sources and the grain boundary diffusion (GBD) technique. TbF3 microparticle-diffused magnets were also prepared for comparison. TbH3 nanoparticles diffusion increased the coercivity by 6.9\u202fkOe for the magnets with thicknesses of 10\u202fmm, which is 5.21\u202fkOe larger than that of TbF3 microparticle-diffused magnets. Deeper, thicker and consecutive (Nd,Tb)2Fe14B layers are observed in TbH3 nanoparticle-diffused magnets compared to TbF3 microparticles, indicating the superiority of TbH3 nanoparticles in the GBD process, which can effectively inhibit the nucleation of reversed domains and thus enhance the coercivity.