Synthesis and characterization of Fe-Ga mixed hydroxide powders

Abstract

Several samples of iron gallium mixed oxyhydroxides with stoichiometry Fe _1–x Ga _x (with x=0, 0.10, 0.25, 0.50, 0.75, 0.90) have been synthesized by a coprecipitation method. They have been characterised from the point of view of their solid state structure by X-ray diffraction (XRD), thermogravimetry and differential thermal analyses (TG-DTA), FTIR and diffuse reflectance (DR) UV-VIS spectroscopy. After drying at 393 K, only one crystalline phase denoted as α-(Fe,Ga)OOH, is found in the samples, i.e. a solid solution in the whole composition range in agreement with the continuous lowering of the unit cell parameter. When Ga is added in small amounts to α-FeOOH, it tends to notably hinder α-(Fe,Ga)OOH crystallisation. The electronic spectra suggest that clustering of Fe ³⁺ in dilute samples may occur. Low-temperature thermal decomposition of such mixed oxyhydroxides gives rise to corundum-hematite type solid solutions in the whole compositional range.