Electron microscopy studies of a TbNiAl compound processed by the HDDR route

A TbNiAl compound processed by the hydrogenation disproportionation desorption recombination route has been studied using a combination of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The SEM backscattered electron (BSE) images showed fine scale composition variations associated with the disproportionation stage while in the recombination stage no structure was visible. TEM examination showed nanocrystalline regions in the disproportionation stage. Selected area diffraction (SAD) showed the existence of two phases TbD2.2 and NiAl in the disproportionation stage and single phase TbNiAl in the recombination stage and the measured d-spacings correlate well with the literature. The distribution of the phases in the disproportionation stage was studied by high-resolution TEM. (C) 2003 Elsevier B.V. All rights reserved.