Structure of UAl4 prepared by solid state reaction

Randomly oriented polycrystalline UA1(4) was obtained by arc melting of Al- 66.7wt.%U alloy followed by a short-time solid state reaction. X-ray powder diffractometer (XRPD), scanning electron microscopy-energy dispersive spec troscopy (SEM-EDS) and density measurements were used in order to determine the exact deviation of stoichiometry in the UA1(4) structure. Machine ball -milled powder samples were used in order to obtain high quality XRPD data, which could be refined by Rietveld method. It was confirmed that only simi lar to 90% of the uranium sites are occupied. There is no evidence for orde ring of vacancies in our samples. (C) 2001 Elsevier Science BY All rights r eserved.