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, thermal stability, and microstructure of Nd22Fe71B7 magnets has been investigated. It has been found that (1) the coercivity is considerably enhanced by the addition of MgO, A12O3, Mg, and Al; and (2) the thermal stability can be improved by the MgO, Al2O3, Mg, and Al additives, especially MgO and A12O3. Microstructural studies reveal that two different intergranular phases appear in the oxide- and pure-element-doped magnets. The modification of the properties can be attributed to the appearance of the phases. It is further found that the introduction of an appropriate amounts of oxygen together with Mg or Al is beneficial for the coercivity and thermal stability of Nd-Fe-B magnets, and the alloying to the intergranular regions (the alloying elements are introduced into intergranular regions) may be a more effective approach to improve the properties of magnets.