Fabrication of Anisotropic Nd–Fe–B Powders by Ta Sputtering

Abstract

The influence of Ta sputtering on the fabrication of anisotropic Nd–Fe–B powders was investigated. X-ray fluorescence and secondary electron microscopy analysis revealed that the measured Ta content after sputtering was 5.6 mass% and the Ta particles were located on the surfaces of the Nd–Fe–B grains. Ta coating on Nd–Fe–B grain could prevent necking between Nd–Fe–B grains after annealing at 700°C for Nd–Fe–B powders with and without Ta sputtering, and the Ta-sputtered powder could be easily crushed.

After crushing and sieving under 75 µm, the coercivity value of the powders with and without Ta sputtering were almost the same, while the anisotropy of Ta-sputtered powder was higher. Upon annealing and crushing, the degree of texture (λ), which is used to evaluate anisotropy, improved from 0.08 to 0.73 for the Ta-sputtered Nd–Fe–B powder and was higher than that for the non-Ta-sputtered Nd–Fe–B powder. The results demonstrate that Ta sputtering can be an effective technique for the fabrication of anisotropic Nd–Fe–B powders.

Fig. 9 Influence of particle size on the coercivity and DOT.