Stoichiometry of Li2MnO3 and LiMn2O4 coexisting phases: XRD and EPR characterization

The coexistence of LiMn2O4 and Li2MnO3 phases from MnO/Li2CO3 mixtures with lithium cationic fraction 0.33 less than or equal to x less than or equal to 0.53 was studied by X-ray diffraction (XRD) and electron paramagnetic resonance (EPR) measurements. XRD quantitative phase analysis was carried out using the Rietveld profile refinement procedure, while the Li2MnO3 percentage was determined directly by comparing the EPR intensities with the intensity of the pure Li2MnO3 spectrum. The experimental results show the presence of an Li-rich spinel phase and allow an estimation of the lithium excess, since the structural analysis of pure Li2MnO3 samples evidenced a nearly stoichiometric composition (x=0.663) with very limited cationic disorder. (C) 1997 Academic Press.