Dy 화합물 혼합에 의한 (Nd, Dy)-Fe-B 소결자석의 자기특성 변화

Abstract

In order to increase the coercivity of (Nd, Dy)-Fe-B sintered magnets without much reduction of remanence, small amount of Dy compounds such as Dy_2O_3 and DyF_3 was mixed with (Nd, Dy)-Fe-B powder. After mixing, the coercivity of (Nd, Dy)-Fe-B sintered magnets apparently increased with the increase of Dy compound in the mixture. Addition of DyF_3 was more effective than Dy_2O_3 for the improvement of coercivity. Reduction of the remanence by the addition of Dy compound, however, was larger than expected mostly due to unresolved coarse Dy compound in the magnet. EPMA analysis revealed that Dy was diffused throughout the grains in the magnet mixed with DyF_3 whereas Dy was rather concentrated around grain boundaries in the magnet mixed with Dy_2O_3.