Transmission electron microscopy studies of sintered Nd-Fe-B magnets prepared by cyclic sintering

Abstract

A cyclic sintering process was demonstrated to achieve higher magnetic and mechanical properties due to homogeneous distribution of the Nd-rich phase during sintering. Densification greater than 98% of the theoretical density was achieved by the cyclic sintering of the Nd-Fe-B powder. In this study, transmission electron microscopy was used to evaluate the microstructural changes of the cyclically sintered Nd-Fe-B magnets. The Nd-rich triple junction phase in the cyclic sintered sample was h-Nd2O3 and the Nd-rich grain boundary phase was a mixture of h-Nd2O3 and h-Nd amorphous thin layers. The coercivity and bending strength increased from 1666.8 to 1828.5 kA/m and from 301.8 to 520 MPa, respectively.