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Dielectric CaF2 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 Nd1-x Cax (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.
Date of Publication: Jan. 2013