Nanosized LiMn2O4 from mechanically activated solid-state synthesis

The synthesis of pure and Cr-doped nanosized LiMn₂O₄ particles has been carried out by solid-state process on high-energy ground mixtures. In situ X-ray analysis demonstrates the spinel forms as single phase at 623 K passing through the Mn₃O₄ precursor at temperatures as low as 573 K. In the doped high-energy ground mixture Li-rich spinel phase forms at 623 K and Cr ions insert in the spinel octahedral site only at 723 K.A mean particle size value of 60 Å, quite independent of the reaction time, is obtained for T<673 K. For higher temperature the growing of the particles as a function of time is observed, independent of doping. The mechanical grinding seems to be the most suitable way to obtain impurity-free spinel phases at lower temperature and with smaller particle size with respect to manually ground mixtures by solid-state reaction and via sol-gel synthesis.