X-ray Diffraction and UV-Visible Characterizations of α-Fe 2 O 3 Nanoparticles Annealed at Different Temperature

Abstract

Effect of annealing on the microstructure, optical absorption properties of hematite (α -Fe2O3) nanoparticles were studied. Crystallite size of α -Fe2O3 increased fro m ~ 34 to 44 n m with increasing annealing temperature fro m 500 to 700℃. St rain in the sample decreased with increasing annealing temperature. UV-visib le characterizat ion indicated the existence of both direct and indirect band gap in the samples. The samp les annealed at all temperatures showed the direct band gap at ~ 2.67 eV. However, the indirect band gap increased from 1.6 to 1.94 eV when the annealing temperature increased fro m 500 to 600℃ and remained almost same for sample annealed at 700℃. The observed values of optical band gaps were in close agreement with the reported values. Ou r results indicated that the thermal annealing would g ive rise to well crystalline α -Fe2O3 nanoparticles with reduced strain.