(1) Laboratoire de Minéralogie-Cristallographie de Paris, Universités Paris 6 et Paris 7, case 115, 4 place Jussieu, 75252 Paris Cedex 05, France, FR
Abstract:
The crystalline structure of Co clusters embedded in an amorphous Al2O3 matrix was studied by transmission electron microscopy (TEM) and electron diffraction (TED). In the first stage of the growth
a metastable structure (body-centred-cubic) is observed. A face-centred-cubic phase (fcc) is found when the size of the clusters
increases ( diameter > 4 nm). The hexagonal-close-packed phase arises in the fcc phase by a succession of stacking faults at the largest sizes.
The mechanisms of phase transformation have been determined by using high resolution electron microscopy (HREM). The chemical
nature of the clusters, in particular the existence of Co-O bonds, was investigated by using electron energy loss spectroscopy
(EELS).
Received 03 July 2000 and Received in final form 22 December 2000