Nickel-induced structural, optical, magnetic, and electrical behavior of α-Fe2O3

We report a simple, eco-friendly facile wet chemical nitrate precursor route for the synthesis of pristine and nickel-containing nanocrystalline (similar to 44 nm) alpha-Fe2O3. Thermal analysis of the dried (similar to 70 degrees C) presumed oxalate powder, Fe-2(C2O4)(3)center dot 4H(2)O (also confirmed by X-ray diffraction), revealed two-step formation of the oxide; slower reaction as Fe-2(C2O4)(3)center dot 4H(2)O down arrow -> 4H(2)O up arrow+2CO(2)up arrow+2FeC(2)O(4)down arrow and faster as 2FeC(2)O(4 ->)Fe(2)O(3)down arrow+CO2 up arrow+3CO up arrow. The incorporation of nickel resulted in progressive increase of cell parameters and exhibited decrease in estimated direct and indirect band gap values. The direct band gap values were in close correlation with emission transitions. The direct nature and narrowing of band gap with nickel addition ensures the higher absorbance values and wider spectrum of absorbance; indicating the enhanced semiconducting properties for applications such as solar cells, photocatalytic activity, etc. Regarding magnetic properties, the saturation magnetization increased progressively with nickel content while coercivity reduced up to 2 wt% of Ni content and increased afterward. The resistivity values with nickel incorporation decreased, when substituted at Fe3+ sites. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim