Electrical Resistivity and Magnetic Performance of Ceramics-Bonded Nd-Fe-B-Type Magnet Consolidated Using Dielectric Oxide Binder

Anisotropic ceramics-bonded Nd-Fe-B-type magnet with high electrical resistivity was fabricated with the intention of suppressing induction of eddy current thus lowering operating temperature of the magnet used as rotor magnet in high-speed motor. The ceramics-bonded Nd-Fe-B-type magnet was fabricated by consolidating mixture of hydrogenation decomposition desorption recombination powder and oxide ceramics with the low melting point. Anisotropic ceramics-bonded (15 vol%) Nd-Fe-B-type magnet had remarkably enhanced electrical resistivity (~ 730 μΩ·cm) with respect to the magnet without ceramics binder (~ 220 μ Ω · cm). Thanks to low-temperature consolidation of Nd-Fe-B-type particles using oxide ceramic binder with low melting point, the detrimental reaction between the magnetic particle surface and oxide was profoundly suppressed, thus retaining the high coercivity of initial magnetic particles even in the ceramics-bonded magnets. Ceramics-bonded (15 vol%) magnet, which had good room temperature magnetic performance (iHc= 12.7 kOe, Mr= 9.4 kG, and (BH)max= 17.0 MGOe) still had reasonably good performance [iHc= 5.0 kOe, Mr= 8.7 kG, and (BH)max= 10.2 MGOe] at 150 °C.