Coercivity enhancement of boron nitride doped Nd15Fe77B8 permanent magnets

Small addition of boron nitride is effective in increasing the Hci value of Nd-Fe-B magnets. With the optimal addition of 0.1 wt% BN, a maximum 20% increase in Hci and a slight increase in Br are obtained, hence (BH)m is slightly enhanced. Chemical compositions estimated by Auger spectroscopy and EPMA indicate that the boron concentration is higher at grain boundaries. The higher concentration of boron can be the result that BN particles react with Nd and dissolve in the Nd-rich phase during the heating processes. Although the dissolved BN contributes to slight grain refining, the coercivity mechanism might be attributed to the change in compositions, notably an increase of NdN and NdB6, and morphology of the intergranular phase