Remanence enhancement in Nd_2Fe_(14)B sintered magnets using fluoride coated FeCo particles

摘要

To provide a high performance composite sintered magnet, Tb-F coated Fe-Co particles were sintered with Nd_2Fe_(14)B. Saturation magnetization is increased with an annealing temperature for Tb-F coated FeCo particles with an average diameter of 30 nm. The saturation magnetization values for Fe_(70)Co_(30) and Fe_(50)Co_(50) particles after annealing at 1050°C are 218 and 210Am~2/kg, respectively, and Nd_2Fe_(14)B/FeCo composite magnets were sintered at 1050°C. Sintered magnets with Tb-F coated Fe_(50)Co_(50) particle show larger remanence and coercivity than those for unadded Nd_2Fe_(14)B sintered magnet. The fluoride layer of Tb-F increases both remanence and coercivity. These increases are attributed to Tb segregation near Nd_2Fe_(14)B/FeCo boundary. As a result, BHmax is increased from 266 kJ/m~3 to 299 kJ/m~3.