High resolution diffraction studies with synchrotron radiation on the structure of Li0.95Mn2.05O4 spinel

Investigations of the structure transformations of lithium deficient Li0.95Mn2.05O4, in the temperature range of 10-1173 K, have been undertaken with X-ray powder diffraction, using synchrotron radiation, at the HASYLAB high-resolution diffractometer (beamline B2). Single phase spinel-like oxide was obtained by a solid state reaction between α-Mn2O3 and Li2CO3 at 1073 K, followed by rapid quenching of the sample in the solid CO2. At the room temperature, the lithium deficient sample (with x = 0.95 in LixMn3−xO4) shows a tetragonally distorted spinel lattice, with c/a = 0.98. No phase transition has been observed when temperature decreased and the sample remained tetragonal in the range 300-10 K. A reversible phase transition appears, however, during very mild heating of Li0.95Mn2.05O4 above the room temperature. The tetragonal spinel structure (F41/ddm) undergoes a transition into cubic form (Fd3m) at 393 K. A thermal treatment above 573 K causes a partial decomposition of the sample, resulting in a formation of a nearly stoichiometric LiMn2O4, with the admixture of manganese oxides.