X-ray powder diffraction and Mössbauer spectroscopic studies on the solubility limits in γ-FeOOH/γ-AIOOH solid solutions
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The formation of substitutional solid solutions between the isostructural γ-FeOOH (lepidocrocite) and γ-AlOOH (boehmite) was investigated by X-ray powder diffraction, Mössbauer spectroscopy, electron microscopic and thermal analysis. Samples of γ-(Fe,Al)OOH were obtained at 15 °C and pH 8 by oxidation of mixed FeCl2-Al(NO3)3 solutions. The unit cell parameters decreased with increasing aluminium content from a=0.3072 nm, b=1.253 nm and c=0.3874 nm, to 0.3053, 1.250 and 0.3858 nm, respectively, The temperature of the differential thermal gravimetry maximum increased with aluminium content up to 10 mol% Al. Quadrupole splitting distribution in the room temperature Mössbauer spectra showed a clear dependence on the concentration of substituted aluminium, enabling determination of the γ-(Fe1−xAlx)1−y/3O1−y(OH)1+y solid solution limits at 0⩽ x⩽ 0.1. The cation deficiency in samples responded to y=0.16 over the whole range of solid solutions formed.
KeywordsSolid Solution Thermal Analysis Unit Cell Parameter Spectroscopic Study Gravimetry
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- 11.E. Wolska and U. Schwertmann, N. Jb. Miner. Mh. 5 (1993) 213.Google Scholar