A new phase in the system lithium–aluminum: Characterization of orthorhombic Li2Al

Investigation of the Li rich part of the binary Li–Al system revealed the existence of a new phase, orthorhombic Li2Al, which is isostructural to Li2Ga and Li2In. The crystal structure was determined from single crystal X-ray diffraction data (Cmcm, a=4.658(2) Å, b=9.767(4) Å, c=4.490(2) Å, Z=4). Refinement of atomic position site occupancies yielded a composition Li1.92Al1.08 (64 at% Li) indicating a small homogeneity range, Li2−xAl1+x. Li2Al is the peritectic decomposition product of the stoichiometric compound Li9Al4, which is stable below 270±2 °C. Li2Al itself decomposes peritectically to Li3Al2 and Li rich melt at 335±2 °C. The discovery of Li2Al (Li2−xAl1+x) settles a long standing inconsistency in the Li–Al phase diagram which was based on the assumption that Li9Al4 possesses a high temperature modification.

A new phase, Li2Al, has been discovered in the binary Li–Al system. The structure of orthorhombic Li2Al is closely related to that of the established monoclinic phase Li9Al4.Figure optionsDownload as PowerPoint slide