Solid state reaction study in the systems Li2CO3-FeC2O4•2H2O and Li2CO3-Fe2(C2O4)3•6H2O

Solid State Reaction study has been performed on the systems Li2CO3-FeC2O4. 2H(2)O and Li2CO3-Fe-2(C2O4)(3). 6H(2)O in the composition range at, (lithium cationic fraction) = 0.10-0.50. By means of high resolution TGA, XRD and DSC, it has been shown that, starting from iron(II) oxalate, Fe2O3 forms which starts to react with Li2CO3 well below its temperature of spontaneous decomposition (ca. 650 degrees C). The reaction product is a mixture of lithium ferrites (LiFe5O8 and LiFeO2) whose relative amounts depend on the starting composition. The microstructure of the ferrites obtained by this system appears to be sensibly different from that of the same compounds prepared from the Li2CO3-Fe2O3 reacting system. High resolution TGA, combined with TG/FT-IR and Diffuse Reflectance FT-IR Spectroscopy, reveals that, in the case of the second system the reaction takes place between iron(III) oxide and lithium carbonate even at lower temperature than it was the case of iron(II) oxalate. The reaction mechanism is rather a complex one but the reaction product is still a mixture of the same lithium ferrites. SEM micrographs showed that, in this case, the ferrite microstructures are quite similar to those formed starting from the reacting system Li2CO3-Fe2O3. (C) 2000 Elsevier Science B.V. All rights reserved.