The status of sintered NdFeB magnets

Since their discovery in 1982, sintered NdFeB magnets have become indispensable components in many high technology products, including high capacity HDD, MRI, windmill generators and high efficiency motors, particularly motors for electric and hybrid vehicles. This chapter provides the current status of sintered NdFeB magnets and begins by discussing the discovery of sintered NdFeB magnets and a detailed discussion of the current manufacturing process. This is followed by a discussion of recent activity aimed at reducing or removing heavy rare earths (HRE) like Tb and Dy from these magnets because these elements are now in short supply. Since 2000, technology to produce magnets with high Br and high coercivity but with reduced amounts of HREs has been developed, including the use of low oxygen processing, grain size refinement techniques, and heavy rare earth grain boundary diffusion processes. Also included are recent developments in better understanding the microstructure of sintered NdFeB magnets and the relationship between microstructure and magnetic performance. The chapter concludes with a discussion of possible technology for producing even higher performance sintered NdFeB magnets.