Annealing temperature effect on structural and optical investigations of Fe2O3 nanostructure

Ferric oxide (Fe2O3) was synthesized at different temperatures (TS) between 300 and 500 °C by spray pyrolysis technique. Surface of annealed Fe2O3 nanostructure was characterized by field emission scanning electron microscopic (FESEM). Annealed Fe2O3 nanostructure has showed rhombohedral hexagonal structure with the preferred orientation along (104) plane in X-ray diffraction patterns (XRD). Crystallite size was increased from 43 to 63 nm with increasing of TS between 300 and 500 °C. The maximum transmittance was found to be 72% for Fe2O3 nanostructure at TS = 300 °C. The energy gap for direct band transitions was measured to be 2.05–2.09 eV. Refractive index of Fe2O3 nanostructure in the visible region was found in the range of 2.37–2.62. Fe2O3 nanostructure has showed n-type electrical conductivity and electrical resistivity was found in the range of 1.02 × 103–6.23 × 103 Ω m. Formation of transparent Fe2O3 nanostructure with band gap and high refractive index suggests the suitability of Fe2O3 nanostructure in gas sensors.