Synthesis and characterization of Fe-Ga mixed hydroxide powders

Several samples of iron gallium mixed oxyhydroxides with stoichiometry Fe1- xGax (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), thermogravimetr y 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 alpha-(Fe,Ga)OOH, is found in the samples, ie. a solid solution in the whole composition range in agreement with the continuous lowering o f the unit cell parameter. When Ga is added in small amounts to FeOOH, it t ends to notably hinder alpha-(Fe,Ga)OOH crystallisation. The electronic spe ctra suggest that clustering of Fe3+ in dilute samples may occur. Low-tempe rature thermal decomposition of such mixed oxyhydroxides gives rise to coru ndum-hematite type solid solutions in the whole compositional range.