Effects of Ru doping and of oxygen vacancies on the optical properties in α-Fe2O3 powders

Abstract

Fe2−xRuxO3 (0 ≤ x≤ 0.08) powders were prepared by solid-state method. X-ray diffraction patterns revealed that the Fe2O3 powders crystallize in a hexagonal structure typical of α-Fe2O3 phase (hematite). The crystallite size was found to decrease from 141 to 84 nm with increasing Ru content from 0 to 0.08, respectively. UV–visible absorption study was performed at room temperature. The direct energy band gap of un-doped α-Fe2O3 was 2.22 eV and found to increase with increasing Ru concentration to reach 2.45 eV for x = 0.08. This increase in band gap was attributed to the decrease in oxygen vacancies with increasing Ru as indicated by calculations of the oxygen occupancy rate using Rietveld refinement. Other properties such as the absorption coefficient, refractive index, the extinction coefficient, real and imaginary dielectric constant, real and imaginary electrical conductivity were calculated using spectrophotometric measurements.