Magnetic properties and microstructure of nanocrystalline bulk Nd-Fe-B with Ce-Co addition

The influence of Ce-Co alloy addition and sintering holding time on permanent magnetic properties and microstructure of nanocrystalline Nd-Fe-B bulk alloy were investigated. The coercivity of Nd-Fe-B bulk alloy can be enhanced greatly by more than 100% after adding Ce-Co powders. However, when the concentration of Ce-Co is up to 30 wt%, the density of the magnet can reach the maximum value of 7.58 g/cm³, but the coercivity does not increase significantly. On the other hand, with the increase of holding time to 10 min, the density and coercivity of magnets increase gradually, reaching up to 7.55 g/cm³ and 1134.3 kA/m, respectively. After the addition of Ce-Co alloy, Ce-Co may easily diffuse into the Nd-Fe-B matrix during hot-pressing and under the high pressure and temperature, thus increasing the content of grain boundary phase and the pinning effect of grain boundary, which leads to the increase of coercivity. The extension of the hot-pressing holding time may be more conducive to the diffusion of Ce-Co into the Nd-Fe-B matrix. In addition, the effect of Ce-Co addition on the magnetic properties of Nd-Fe-B with different content of rare earth was also studied. The addition of Ce-Co can effectively increase the coercivity of nanocomposite Nd₂Fe₁₄B/α-Fe magnets. The addition of Nb to the parent alloy can further improve the coercivity. For Nd₁₁Fe_81.5Nb₁Ga_0.5B₆ alloy with 10 wt% Ce-Co addition, the coercivity can increase from 740.28 to 1098.48 kA/m.