Correlative multi-scale characterization of a fine grained Nd–Fe–B sintered magnet

The Nd-rich phases in pressless processed fine grained Nd–Fe–B sintered magnets have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and three dimensional atom probe tomography (3DAP). The combination of the backscattered electron (BSE) and in-lens secondary electron (IL-SE) images in SEM led to an unambiguous identification of four types of Nd-rich phases, NdOx, Ia3¯ type phase, which is isostructural to Nd2O3, dhcp-Nd and Nd1Fe4B4. In addition, the 3DAP analysis of thin Nd-rich grain boundary layer indicate that the coercivity has a close correlation with the chemistry of the grain boundary phase.

► Multi-scale characterization of Nd–Fe–B sintered magnet by SEM/TEM/3DAP.
► Phase/chemistry identification of Nd-rich phases at grain boundary triple junctions.
► Identification of micron-scale distribution of Nd-rich phases by IL-SE and BSE SEM.
► Correlative SEM/3DAP analysis from a specific thin grain boundary phase.