Inequality of quenched and high temperature structure of lithium deficient LiMn2O4

Structural characterization of the new low temperature polymorph of the lithium-deficient lithium-manganese spinel, synthesized and quenched from 1073 K has been obtained by Rietveld structure refinements of X-ray powder diffraction data recorded using synchrotron radiation. A slight lithium ions deficiency causes formation of the tetragonal phase provided that the samples obtained at high temperature are rapidly quenched in the solid CO2. The new phase has a tetragonally distorted spinel structure at 140 K with a space group F41/ddm, unit cells of a = 8.33180(6) Å and c = 8.08617(7) Å. On heating, at 280 K, the tetragonal phase transforms to cubic spinel structure (Fd3m) and it remains cubic up to 1163 K.