Micron-scale 1:5H-based precipitated phase with the lamellar structure of sintered Sm_(2)Co_(17)-based magnets and its potential application

The excellent thermal stability of magnetic properties of Sm_(2)Co_(17)-based magnets is their most impor-tant feature.However,this stability is reduced when the maximum energy product of Sm_(2)Co_(17)-based magnets is improved,which is mainly determined by the Fe/Cu distribution of the 2:17R cell and 1:5H cell boundary phases.During the demagnetization process,the Cu-rich 1:5H cell boundary phase with a width of 2-15 nm obstructs the motion of the domain walls,yielding coercivity.Herein,we report a micron-scale Cu/Zr-rich and Fe-lean 1:5H-based precipitated phase with a lamellar structure,probably induced by Sm_(2)O_(3) doping.This structure enables the separate regulation of Fe and Cu distribution for Sm_(2)Co_(17)-based magnets with Fe-rich 2:17R cell phases and Cu-rich 1:5H cell boundary phases,consid-erably optimizing the thermal stability of magnetic properties.This discovery can be further developed to produce Sm_(2)Co_(17)-based magnets with high performance and excellent thermal stability of magnetic properties.

Magnetic properties and microstructure of Fe69.5-xNd7B21Nb2.5Gax（x=0-1）alloys

The Fe69.5-xNd7 B21Nb2.5Gax(x = 0-1)permanent magnets in the form of rods were prepared by annealing the bulk amorphous alloys.The magnetic properties,phase evolution and microstructure of the alloys were investigated systematically.It is found that the glass forming ability(GFA), microstructure and magnetic properties are sensitive to Ga content for Fe69.5-xNd7 B21Nb2.5Gax(x = 0-1)bulk alloys.The annealed alloys are mainly composed of soft α-Fe,hard Nd2 Fe14B and nonmagnetic Nd1.1Fe4 B4 phases.When x = 0.3,the optimally annealed magnets exhibit magnetic properties of the remanence Br = 0.63 T,intrinsic coercivity Hcj = 368.68 kA/m and maximum energy product(BH)max = 33.73 kJ/m3.Furthermore,magnetic field heat treatment at the temperature close to Curie temperature of Nd2 Fe14B phase was applied to the annealed Fe69.2Nd7 B21Nb2.5Ga0.3 magnet.The results of X-ray diffraction(XRD)and transmission electron microscopy(TEM)indicate that the magnetic field heat treatment can be beneficial for the precipitation of α-Fe.Thus,the Br,Hcj and(BH)max are enhanced by 8.7%,6.3% and 16.3%,respectively.