Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1624783 | Journal of Alloys and Compounds | 2008 | 12 Pages |
Combined synchrotron in situ X-ray diffraction and neutron diffraction studies were performed on 2:1 mixtures of lithium amide and magnesium hydride, which have shown promise as solid-state hydrogen storage materials. The dehydrogenated product is a mixed lithium and magnesium imide, Li2Mg(NH)2, whose crystal structure has not heretofore been determined. Furthermore, at elevated temperatures, Li2Mg(NH)2 undergoes two structural transitions from an orthorhombic structure to a primitive cubic structure at intermediate temperature (350 °C) followed by a face-centered cubic crystal structure at high temperature (500 °C). Disordering of the Li, Mg and cation vacancies as a function of temperature drives the structural transitions. We report the reaction pathway from in situ X-ray diffraction studies and the crystal structures of the three structural variants of Li2Mg(NH)2 as determined by high-resolution X-ray and neutron powder diffraction. We also report the hydrogen storage reaction pathways for mixtures with other cation ratios.