Transmission electron microscopy study of high energy product Fe-Nd-B ribbons

Transmission electron microscopy has been used to characterize the microstructure and crystal structure of high energy product (14.1 MG.Oe) melt-spun Fe-Nd-B ribbons with an alloy composition of Nd13Fe82.6,B4.4. The microstructure of these ribbons consists of very fine grains, and they are practically single-phase materials. It appears that there are also very thin grain boundary films surrounding the grains. The grain size varies from 10 to 80 nm, with an average of about 15 nm. The crystal structure of these ribbons was also studied by using electron diffraction analysis. All the diffraction patterns can be fitted very well by a tetragonal structure with lattice parameters a = 0.880 nm and c = 1.218 nm, in very good agreement with x-ray diffraction and neutron diffraction results. The superior magnetic properties are probably due to the fine-grained Nd2Fe14B compound in these ribbons (i.e., single-domain fine particles).