Progress in recycling of Nd-Fe-B sintered magnet wastes

Significant efforts have been put into the recycling of bulk Nd-Fe-B sintered magnet wastes around the world in the past decade because bulk Nd-Fe-B sintered magnet wastes are valuable secondary rare-earth resources. There are two major facts behind the efforts. First, the waste magnets contain total rare-earth content as high as more than 30 wt.%, which is higher than most natural rare-earth mines. Second, the waste magnets maintain the physical and chemical properties of the original magnets even with deterioration of the properties on surfaces due to corrosion and contamination. In this review, various techniques for recycling bulk Nd-Fe-B sintered magnet wastes, the overall properties of the recycled Nd-Fe-B sintered magnets, and the mass production of recycled magnets from the wastes are reviewed.