Improvement of magnetic properties and corrosion resistance of NdFeB magnets by intergranular addition of MgO

In this work we have studied the effects of MgO addition on magnetic properties and corrosion resistance of NdFeB magnets. We have found that remanence and density of the magnet can be increased by intergranular addition of MgO. For Nd15Dy1.2FebalAl0.8B6 magnets with 0.1-0.3 wt.% MgO addition, corrosion potential of magnets is more positive, and polarization current density under the same applied potential in the anodic branch of the polarization curve is lowered compared with magnet without additives. This indicates that intergranular addition of MgO can improve the corrosion resistance of magnets. Furthermore, oxidation test also indicates the magnets with MgO addition are more resistant to humid environment. Enhance of corrosion resistance of magnets is believed to be due to the formation of a Nd-O-Fe-Mg intergranular phase. (C) 2007 Elsevier B.V. All rights reserved.