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

High coercivities mu(0i)H(C) of 1.8 and 2.0 T, twice as high as previously reported, remanences B-r of 0.63 and 0.69 T, and maximum energy products (B H)(max) of 70 and 89 kJ/m(3) at 293 K are achieved for Nd13Dy2Fe77C8-xBx ri bbons with x=0 and 2 after optimum heat treatment, respectively. The sample s prepared by rapid quenching and short-time vacuum annealing are of tetrag onal 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 di rectly 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. ( C) 2000 American Institute of Physics. [S0003-6951(00)00624-0].