High coercivity of Nd–Dy–Fe–(C, B) ribbons prepared by melt spinning

High coercivities μ0iHC of 1.8 and 2.0 T, twice as high as previously reported, remanences Br of 0.63 and 0.69 T, and maximum energy products (BH)max of 70 and 89 kJ/m3 at 293 K are achieved for Nd13Dy2Fe77C8−xBx ribbons with x=0 and 2 after optimum heat treatment, respectively. The samples prepared by rapid quenching and short-time vacuum annealing are of tetragonal Nd2Fe14B (2:14:1)-type structure. It was confirmed that boron addition accelerates the formation of the 2:14:1-type structure, which is formed directly from melt spinning. A very high coercivity of 2.5 T was observed for as-quenched Nd13Dy2Fe77C6B2 ribbons, however with poorer B–H-loop shape.