The influence of Ga-substitution on the coercivity of Nd-(Fe,Co)-B sintered permanent magnets

In Co-substituted Nd-Fe-B sintered magnets, several additional phases such as Nd(Fe,Co)/sub y/B/sub ?/ with y=2, 3, and 4 have been found besides the hard magnetic phase and the Nd-rich intergranular phase. The low coercivity of the magnet is attributed to the occurrence of these soft ferromagnetic phases. In Ga-doped Nd-(Fe,Co)-B sintered magnets, new intergranular phases such as Nd(Ga,Fe,Co) and Nd(Ga,Fe,Co)/sub 2/ have been found instead of the soft ferromagnetic Co-rich phases. From X-ray microanalysis data it is concluded that Ga substitutes the transition-metal atoms in the 2:14:1-phase, and Ga is not detected in the Nd-rich phase at all. The increase of the coercivity of Ga-doped magnets is correlated to a higher volume fraction of intergranular phases and an increased wetting during sintering due to these phases.<
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