Internally Segmented Nd-Fe-B/CaF2 Sintered Magnets

Dielectric CaF
₂
layers were introduced into Nd-Fe-Co-Ga-B green compacts which were subsequently sintered into internally segmented anisotropic magnets. Layers with the nominal area density of 0.2-0.3 mg CaF
₂
per mm
²
were found to increase the electrical resistivity by two orders of magnitude while still allowing the magnets to be cut and polished. The internal segmentation with CaF
₂
fully preserves the coercivity of the magnets and is accompanied by only a small decline of the magnet remanence. The fcc Nd
_1-
x
Ca
x
(F,O)
_δ
phase produced by the reaction between the CaF
₂
phase and the Nd-rich phase is believed to improve the metallurgical bond between the dielectric layers and magnet matrix. The internal segmentation may be a cost-effective way of manufacturing Nd-Fe-B sintered magnets with low eddy current losses, suitable for motor/generator applications.