Microstructure and magnetic properties of isotropic bulk NdxFe94-xB6 (x=6,8,10) nanocomposite magnets prepared by spark plasma sintering

Nd2Fe14B/alpha-Fe isotropic bulk nanocomposite magnets were prepared by spark plasma sintering (SPS) technique using melt-spun powders with a nominated composition of NdxFe94-xB6, with x=6, 8, and 10. It was found that higher sintering temperature improved the densification of the magnets, while it deteriorated their magnetic properties simultaneously due to the excess crystal grain growth. An increased compressive pressure led to better magnetic properties and higher density for the SPS magnets. An increase in the Nd amount resulted in a gradual increase in intrinsic coercivity and an obvious reduction of the remanence of the magnets simultaneously. A magnet with the composition of Nd8Fe86B6 possessed a B-r of 0.99 T, a H-ci of 386 kA/m, and a (BH)(max) of 101 kJ/m(3) under the optimal sintering condition. In addition, microstructure observation using transmission electron microscopy showed that compared with the starting powders the full-density magnets nearly maintain the morphology, indicating that there was no sign of pronounced crystal grain growth during the densification process. (C) 2006 American Institute of Physics.