Hydrothermal synthesis and structural characterization of (1−x)α-Fe2O3–xSnO2 nanoparticles Original Research Article

Structural and morphological characteristics of (1−x)α-Fe2O3–xSnO2 (x=0.0–1.0) nanoparticles obtained under hydrothermal conditions have been investigated by X-ray diffraction (XRD), transmission Mössbauer spectroscopy, scanning and transmission electron microscopy as well as energy dispersive X-ray analysis. On the basis of the Rietveld structure refinements of the XRD spectra at low tin concentrations, it was found that Sn4+ ions partially substitute for Fe3+ at the octahedral sites and also occupy the interstitial octahedral sites which are vacant in α-Fe2O3 corundum structure. A phase separation of α-Fe2O3 and SnO2 was observed for x≥0.4: the α-Fe2O3 structure containing tin decreases simultaneously with the increase of the SnO2 phase containing substitutional iron ions. The mean particle dimension decreases from 70 to 6 nm, as the molar fraction x increases up to x=1.0. The estimated solubility limits in the nanoparticle system (1−x)α-Fe2O3–xSnO2 synthesized under hydrothermal conditions are: x≤0.2 for Sn4+ in α-Fe2O3 and x≥0.7 for Fe3+ in SnO2.