Phase composition, microstructure, and optical characteristics of spin‐coated La‐TiO ₂ and Fe‐TiO ₂

Herein, TiO 2 , La‐added, and Fe‐added TiO 2 coatings are synthesized by sol–gel spin coating using acid catalyst‐free titania precursors, and their microstructural and optical characteristics are studied. The possible reaction mechanism for synthesizing TiO 2 ‐based coatings using catalyst‐free precursor is presented and correlated to their microstructural characteristic. TiO 2 coatings are developed and found to be anatase in phases having submicron morphological features. The anatase composition of TiO 2 coating decreases with increasing La or Fe ion concentrations. This manifests the inhibitory effect of increasing La and Fe ions to the formation of anatase TiO 2 . Moreover, the addition of La ions caused no significant changes in the reflectance spectra and bandgap energy of TiO 2 . In contrast, a remarkable red shift was observed with increasing Fe ion concentration. The calculated bandgap decreases from 3.261 to 2.096 eV with the addition of 7.5 mol% Fe ions, attributed to the formation of new energy states below the conduction band of TiO 2 induced by the Fe ion. These results suggested that a low‐cost Fe added‐TiO 2 material can be synthesized using an acid catalyst‐free precursor that could extend the photocatalytic efficiency of TiO 2 to the visible light region.