Improvement of thermal stability of Nd-Dy-Fe-Co-B sintered magnets by additions of Al, Nd and Ga

To improve the thermal stability of (Nd0.8Dy0.2) (Fe0.86Co0.06B0.08)5.5 sintered magnets for heavy duty applications, such as starter motors, effects of additional elements(M=Al, Nb and Ga) On the thermal stability were investigated in the (Nd0.8Dy0.2) (Fe0.86-u-Co0.06B0.08Mu)5.5 sintered magnets. The addition of Al increasediHc, but did not decreased irreversible losses at 220°C(Pc= 2). The sintered magnet with M=Nb and u=0.006 had loweriHcand higher irreversible losses than u=0, while the sintered magnet with M=Nb and u=0.015 had higheriHcand lower irreversible losses. Additions of Ga were resulted in higheriHcand lower irreversible losses. A combination of both Nb and Ga additions was also studied and a very low irreversible loss of under 5 % after exposure at 260°C(Pc= 2) was obtained for (Nd0.8Dy0.2) (Fe0.835Co0.06B0.08Nb0.015Ga0.01)5.5 sintered magnets. The obtained magnetic properties for the magnet are Br=10450 G,bHc=10000 Oe,iHc=27100 Oe and MGOe.