Magnetic and Microstructural Characteristics of Nd-Fe-B Sintered Magnets Doped With Dy $_2$O$_3$ and DyF $_3$ Powders

Magnetic and microstructural properties of (Nd
$_{26.06}$
, Dy
$_{6.51}$
)-Fe
$_{\rm bal.}$
-B
$_{0.97}$
-M
$_{2.39}$
(wt.%) (
${\rm M} = {\rm Cu},\ {\rm Al},\ {\rm Co}$
, and Nb) sintered magnets doped with Dy
$_{2}$
O
$_{3}$
and DyF
$_{3}$
powders were studied. In the case of the Dy
$_{2}$
O
$_{3}$
-doped magnet, Dy was distributed along the near grain boundaries. In contrast, the DyF
$_{3}$
-doped magnet and the undoped magnet showed that Dy was distributed uniformly in the main phase. The coercivity and the remanence of the Dy
$_{2}$
O
$_{3}$
and DyF
$_{3}$
-doped magnets were 33.2 kOe, 11.64 kG, and 34.5 kOe, 11.21 kG, respectively. The coercivity of the DyF
$_{3}$
-doped magnet was the largest but its remanence was the smallest among other magnets because the Dy was distributed throughout the main phase. Uniform distribution of the Dy in the DyF
$_{3}$
-doped magnet was probably due to their lower bonding energy and higher chemical potential for diffusion.