Sandwich-Shell Structure in Grain Boundary Diffused (Ce,Y,La)–Fe–B Magnet

摘要

Grain boundary diffusion (GBD) process improved the coercivity and the thermal stability of magnets by the core–shell-type reaction phases formed between the Nd ₂ Fe ^{14 B matrix grains and heavy rare-earth. Sintered (Ce–Y–La)–Fe–B magnet GBD processed at 940 °C for 10 h with TbHx source was prepared. Sandwich structure with (Ce,Y) ₂ Fe 14 B, (Tb,Ce,Y) ₂ Fe 14 B, and (Ce,Tb,Y) ₂ Fe 14 B shells was formed around the Y-rich core in the GBD processed matrix grains. Formation mechanism of the sandwich-shell core structure was proposed and discussed.}