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Grain boundary diffusion technique with TbH3 nanoparticles was applied to fabricate Tb-less sintered Nd-Fe-B permanent magnets with high coercivity.The magnetic properties and microstructure of magnets were systematically studied.The coercivity and remanence of grain boundary diffusion magnet are improved by 112 ％ and reduced by 26 ％ compared with those of the original magnet,respectively.Meanwhile,both the remanence temperature coefficient (α) and the coercivity temperature coefficient (β) of the magnets are improved after diffusion treatment.Microstructure shows that Tb element enriches in the surface region of Nd2Fe14B grains and is expected to exist as (Nd,Tb)2Fe14B phase.Thus,the magneto-crystalline anisotropy field of the magnet improves remarkably.As a result,the sintered Nd-Fe-B magnets by grain boundary diffusion with TbH3 nanoparticles exhibit enhanced coercivity.