Solid state reaction study in the systems Li 2CO 3–FeC 2O 4·2H 2O and Li 2CO 3–Fe 2(C 2O 4) 3·6H 2O

Abstract

Solid State Reaction study has been performed on the systems Li 2CO 3–FeC 2O 4·2H 2O and Li 2CO 3–Fe 2(C 2O 4) 3·6H 2O in the composition range x Li (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, Fe 2O 3 forms which starts to react with Li 2CO 3 well below its temperature of spontaneous decomposition (ca. 650°C). The reaction product is a mixture of lithium ferrites (LiFe 5O 8 and LiFeO 2) 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 Li 2CO 3–Fe 2O 3 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 Li 2CO 3–Fe 2O 3.