engleski

Influence of Cr doping on the structural, magnetic, optical and photocatalytic properties of α-Fe2O3 nanorods

Pure and Cr-doped hematite (α-(Fe1-xCrx)2O3, x = 0, 0.026, 0.039, 0.085 or 0.135) nanorods were prepared by a simple co-precipitation and calcination method. Influence of different levels of Cr doping on the change of properties of long and thin pure hematite nanorods was investigated. Cr3+-for-Fe3+ substitution in the crystal structure of hematite was proved by measuring a gradual contraction of the unit cell and a gradual decrease of the hyperfine magnetic field by increasing the Cr molar fraction. Cr doping induced an increase in the width and thickness of hematite nanorods, as well as a decrease in the overall surface area. Low temperature 57Fe Mossbauer ¨ spectroscopy showed that the Morin transition in hematite was suppressed by Cr doping to temperatures below 80 K. Magnetic measurements confirmed the suppression of the Morin transition in Cr-doped hematite down to 5 K. Infrared spectra of Cr- doped hematite samples showed shifts of IR bands by Cr3+-forFe3+ substitution. Optical properties of α-Fe2O3 nanorods changed significantly by Cr doping – the absorption edge was shifted to higher wavelengths, accompanied by a greater absorption in the visible range and narrowed direct and indirect optical band gaps. The improved visible light photocatalytic activity of hematite nanorods in the heterogeneous photo-Fenton process by moderate Cr doping was measured, which can be attributed to the modifications in electronic structure and optical properties.

Hematite ; Cr dopant ; Mössbauer spectroscopy ; Morin transition ; Optical band gap

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