Effect of sintering conditions on the magnetic and microstructural properties of Nd-Fe-B sintered magnets doped with DyF(3) powders.

The microstructural and magnetic property changes of DyF(3)-doped (Nd(26.06), Dy(6.51))-Fe(bal) -B(0.97)-M(2.39) (wt. %) (M = Cu, Al, Co, and Nb) sintered magnets as functions of the sintering conditions were studied. The sintering conditions for the optimum core-shell microstructure were determined. When the magnets were sintered at 1050 °C for 4 h, a coercivity of 35.1 kOe was obtained without sacrificing the remanence. When the magnets were doped with DyF(3), the formation of the RE-rich phase (Nd-Dy-O) was effectively suppressed and, hence, saving the Dy. In addition, the formation of a cubic-NdOF triple-junction phase (TJP) improves the interface uniformity and enhances the coercivity.