Synchrotron X-ray and neutron diffraction studies of NaAlH4 containing Ti additives

NaAlH4, Na3AlH6 and NaH samples with Ti additives have been investigated by synchrotron X-ray diffraction and neutron diffraction. Directly after ball milling there are no signs of any Ti-containing phases, and the unit-cell dimensions of NaAlH4, Na3AlH6 and Al give no indication of any solid solutions. Combined refinements of X-ray and neutron diffraction of Na1-3xTixAlD4 and NaAl1-xTixD4 show no indications of such solid solutions. Hence it is concluded that the Ti is in an amorphous state directly after ball milling. After cycling, however, a shoulder on the high-angle side of the Al reflections appears that is interpreted as a fee solid solution Al1-xTix with x approximate to 0.07. Furthermore, addition of TiF3 by ball milling results in different phases compared to TiCl3/TiCl4. The chlorides give NaCl, whereas no NaF is formed by the fluoro, additive. It has not yet been possible to determine by X-ray diffraction where the fluorine is in the sample. (C) 2004 Elsevier B.V. All rights reserved.