Phase Composition, Microstructure, and Optical Characteristics of Spin‐Coated La‐TiO₂ and Fe–TiO₂

Abstract

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.