Effect of DyF3 additions on the coercivity and grain boundary structure in sintered Nd–Fe–B magnets

Coercivity of Nd–Fe–B sintered magnets was obviously enhanced by DyF3 additions with little sacrifice of remanence and squareness factor. An ordered rare-earth oxyfluoride grain boundary phase containing ∼30 at.% F was formed. In addition, the presence of F decreased the thickness of the region of reduced anisotropy of the Nd2Fe14B grain. Dy segregated on the surface of the Nd2Fe14B grains. The individual effects of F and Dy elements on the increased coercivity are discussed based on these results.