Tailoring the structural and optical characteristics of hematite (α-Fe2O3) nanostructures by barium/aluminum dual doping for eco-friendly applications

In the current work, the structural and optical characteristics of hematite (alpha-Fe2O3) have been tailored by individual and dual doping of Ba and Al for photocatalytic and eco-friendly applications. The doped and undoped hematite nanostructures were synthesized onto quartz substrates via the spray pyrolysis route. The surfaces' morphology, vibrational bands and structural properties were investigated based on FE-SEM, FT-IR and XRD measurements, respectively. The XRD analysis reveals that all samples have a rhombohedral hematite structure. The crystallite size varies from 20.8 nm (undoped hematite) to 27.6 nm (Ba-doped hematite), 24.3 nm (Al-doped hematite) and 22.8 nm (Ba/Al dual doped hematite). The optical transmittance, absorbance and reflectance spectra were recorded by a UV-Vis-NIR spectrophotometer. The UV-Vis-NIR analysis shows that Ba/Al dual doped hematite film possesses an optimal absorption amount in the region where the wavelength lambda > 561 nm. The direct energy band gap (E-g) changes from 2.30 eV (undoped hematite) to 2.42 eV nm (Ba-doped hematite), 2.18 eV nm (Al-doped hematite) and 2.22 eV nm (Ba/Al dual doped hematite). Clear enhancement in the refractive index (n), dielectric constants and optical conductivity of the hematite NPs is attained via individual or dual doping of Ba and Al elements. For example, at lambda = 550 nm, n of the undoped hematite increases from 1.88 to 1.91 (Ba-doped hematite), 2.07 (Al-doped hematite) and 1.97 (Ba/Al dual doped hematite). These novel results nominate the individual Ba, Al and Ba/Al dual doped hematite NPs for applications in photocatalysts and eco-friendly devices.