Abstract
Dysprosium-added sintered magnets were prepared from blends of Nd15.5(Fe,Co,Ga)78.2B6.3 and Dy2S3 powders; their microstructure and magnetic properties were compared to those of the magnets made with Dy2O3 additions or from single (Nd,Dy)-(Fe,Co,Ga)-B alloys. The addition of Dy2S3 leads to replacement of the neodymium oxide phases in the sintered magnets by the Nd2O2S and NdS phases. The magnets prepared with both the Dy2S3 and Dy2O3 powders exhibited inhomogeneous distribution of Dy within the (Nd,Dy)2Fe14B grains with Dy-rich outer grain regions. However, in a marked difference from the Dy2O3-added and single-alloy magnets, where the grain-boundary oxide phases were Dy-rich, the magnets prepared with Dy2S3 had their sulfur-containing grain-boundary phases depleted of Dy. With the larger fraction of Dy atoms available for alloying the main (Nd,Dy)2Fe14B phase, the magnets prepared with Dy2S3 showed the largest coercivity gain per 1 at.% of the added Dy.
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