Internally Segmented Nd-Fe-B/CaF2Sintered Magnets

Dielectric CaF2layers 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 CaF2per mm2were 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 CaF2fully preserves the coercivity of the magnets and is accompanied by only a small decline of the magnet remanence. The fcc Nd1-xCax(F,O)δphase produced by the reaction between the CaF2phase 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.