In situ TEM study of Nd-rich phase in NdFeB magnet

Hot stage in transmission electron microscope has been used to study the structure and stability of Nd-rich phase in NdFeB magnet. The present observation shows that the so-called complex cubic phase is in fact the prototype of n(2)O(3) (space group Ia3) with lattice parameter of a = 1.08 urn. The Nd-rich phase with P3mI structure (h-Nd2O3) was first observed to be transformed from the BCC phase after in situ heating over 400 degreesC. The orientation relationship between these two structures satisfies as follows: (0001)(HCP)//(200)(BCC:) (1010)(HCP)//(020)(BCC),(1210)(HCP)//(001)(BCC). It is argued that the h-Nd2O3 was arising from the oxidation of the BCC Nd-rich phase rather than from NA(z)Fe(z)B matrix phase as suggested in the literature. (C) 2004 Elsevier B.V. All rights reserved.