Magnetic Properties and Thermal Stability of Sintered Nd-Fe-B Magnet with Dy-Ni Additive

A sintered（Nd_（0.8）Pr_（0.2））_（30.7）FebalB_（0.98）Cu_（0.2） magnet with 3% intergranular Dy_（85）Ni_（15） additive is prepared to study the magnetic properties and thermal stability of the Nd-Fe-B magnet. The results show that the magnet with or without additive obtains its optimum comprehensive magnetic properties at the sintering temperature of 1 030 ℃ and 1 040 ℃, respectively. The maximum coercivity of the magnet with additive reaches 15.16 k Oe, while that of the magnet without additive is just 11.88 k Oe. Further investigation on microstructure indicates that the grains of the magnet with additive form a modified ＂core shell＂ structure. Adding Dy_（85）Ni_（15） can significantly enhance the coercivity of Nd-Fe-B magnet and thus decrease its coercivity temperature coefficient.

Coercivity Enhancement of the Sintered Nd-Fe-B Magnet with Intergranular Multi-Addition

In order to improve the coercivity of the sintered Nd-Fe-B magnet,a Nd13.5Fe79.75B6.75magnet with intergranular multi-addition of 2%Dy H3,2%Nd H3and 1%Nd2O3is prepared and its magnetic property and microstructure are analyzed.The results show that the coercivity of the magnet with multi-addition is as high as 1 300 k A/m,while that of the magnets with Dy H3and Nd2O3are 520 k A/m and 850 k A/m,respectively.Scanning electron microscope（SEM）shows that the grain boundaries in the magnet with multi-addition are smoother and the grain size is smaller than that in the magnet without the addition.Compared with addition of Dy H3or Nd2O3,the multi-addition can more effectively enhance coercivity of the magnet.Intergranular adding process with multi-addition can both increase the anisotropy field and optimize the grain-boundary microstructure of the magnet.As a result,the coercivity of the magnet is significantly increased.