Synchrotron X-ray studies of Ti-doped NaAlH4.

Pure and doped NaAlH(4) with 5 mol % Ti on the basis of Ti(13).6THF have been investigated by means of X-ray synchrotron radiation. The Rietveld method has been used to study the possible substitution of Ti inside the NaAlH(4) structure and/or the presence of vacancies. This study indicates that there is no significant variation of the lattice parameter once the Na Alanate is doped with the Ti cluster. From the refinement of the site occupation factors, the substitution of Ti on the Na site can be excluded. A slight improvement was found when Ti was substituted on the Al site, but it is not significant enough to say that Ti definitely substitutes for Al in the Alanate phase. Additionally, there is no evidence for vacancy formation in Ti-colloid-doped sodium Alanate.