Thermoanalytical (TGA-DSC) and High Temperature X-Ray Diffraction (HT-XRD) Study of the Thermal Decomposition Processes in Li2CO3 – MnO Mixtures

The thermal decomposition processes taking place in solid state mixtures Li2CO3–MnO (XLi=0.10–0.50, XLi=lithium cathionic fraction) have been studied (in air) by High Resolution Thermogravimetric Analysis (HRes-TGA), Heat Flux Differential Scanning Calorimetry (Heat Flux-DSC) and temperature variable X-ray Powder Diffractometry (HT-XRPD), in order to get a better understanding of the intermediate reaction stages and to assess the equilibrium compounds as well. As concerns the measurements performed on mixtures with XLi0.333, LiMn2O4 and excess Mn2O3 are the obtained equilibrium products. By 0.33XLi0.50 a mixture of LiMn2O4 and Li2MnO3 is obtained whose proportions depend on the reaction path followed. A stoichiometric model, where both lithium manganese oxides form simultaneously, holds for XLi=0.45 and 0.50 mixtures. A two stage model, where Li2MnO3 forms first, followed by reaction with excess Mn2O3 to yield LiMn2O4, is the reaction path for the XLi=0.35 mixture.