Solid-solid interaction between ferric oxide and manganese carbonate as influenced by lithium oxide doping

The solid-solid interaction between pure and lithia-doped manganese and ferric oxides have been investigated using DTA and XRD techniques. Equimolar proportions of manganese carbonate and ferric oxide were employed, while the dopant substrate was added as lithium nitrate, The amounts of dopant were 0.89, 1.68 and 3.36 mol% Li2O. The results obtained revealed that the thermal treatment of manganese carbonate and ferric oxide at 800 degreesC resulted in the formation of Mn2O3 (Partridgeite) and alpha -Fe2O3 phases having an excellent degree of crystallinity. Solid-solid interaction took place between the produced oxides at temperatures starting from 900 degreesC yielding MnFe2O4 (Jacobsite). The degree of propagation of this reaction was found to increase by increasing both the precalcination temperature and the amount of Li2O added. The progressive increase in the height of the diffraction line of MnFe2O4 at "d" spacing of 2.56 Angstrom (100%) as a function of precalcination temperature for pure and variously doped mixed solids was utilized in the determination of activation energy of formation of manganese ferrite (DeltaE). The computed DeltaE values were 174, 153, 134 and 117 kJ mol(-1) for pure mixed solids and those doped with 0.84, 1.68 and 3.36 mol% Li2O. These results were discussed in terms of dissolution of lithium cations in the lattices of Fe2O3 and Mn2O3 solids with subsequent increase in the mobility of the reacting ferric and manganese cations. (C) 2001 Elsevier Science B.V. All rights reserved.