THE INFLUENCE OF MGO MG AND AL2O3/AL ADDITIVES ON COERCIVITY, THERMAL-STABILITY, AND MICROSTRUCTURE OF ND-FE-B MAGNETS/

The influence of MgO/Mg and Al2O3/Al addition on the coercivity, therm al stability, and microstructure of Nd22Fe71B7 magnets has been invest igated. It has been found that (1) the coercivity is considerably enha nced by the addition of MgO, Al2O3, Mg, and Al; and (2) the thermal st ability can be improved by the MgO, Al2O3, Mg, and Al additives, espec ially MgO and Al2O3. Microstructural studies reveal that two different intergranular phases appear in the oxide- and pure-element-doped magn ets. The modification of the properties can be attributed to the appea rance of the phases. It is further found that the introduction of an a ppropriate amounts of oxygen together with Mg or Al is beneficial for the coercivity and thermal stability of Nd-Fe B magnets, and the alloy ing to the intergranular regions (the alloying elements are introduced into intergranular regions) may be a more effective approach to impro ve the properties of magnets.