Microstructure and Magnetic Properties of NdFeB Magnets Using Fluorides Nano-coated Process

摘要

Nd_2Fe_(14)B magnets could be sintered using terbium fluoride coated Nd_2Fe_(14)B powders. Fluorine atoms were segregated at the triple junctions and grain boundary after sintering and aging process. NdOF with fcc structure was grown at the triple junction. Terbium atoms were also distributed near grain boundaries by interdiffusion between the fluoride and Nd_2Fe_(14)B. No fluorine atoms were detected in Nd_2Fe_(14)B phase. The coercivity for 0.5 wt% terbium fluoride coated magnet showed 1.23 MA/m which was 1.2 times higher than that for non-coated magnet with 1.04 MA/m. The distribution of terbium and fluorine atoms increases the coercivity without reduction of remanence.