Effect of Yttrium Doping on Titanium Dioxide

The wide band gap and chemical–mechanical stability of titanium dioxide (TiO$_2$) make it one of the most important semiconductor materials for photocatalytic applications. However, its performance is limited by its low absorption in the visible light region. In this study, yttrium (Y)-doped TiO$_2$ (Y/TiO$_2$) powders containing 1%, 5%, and 10% Y were synthesized via the sol–gel method to improve visible-light absorption. The effects of Y doping on morphology, elemental composition, crystal structure, optical properties, and photocatalytic activity were investigated using a range of analytical techniques, including SEM/EDS, XRD, particle size analysis, and UV-Vis spectroscopy. The synthesized Y/TiO$_2$ samples exhibited spherical morphology, with the average particle sizes decreasing from 232 nm (pure TiO$_2$) to 50.24 nm (5% Y doping). Y doping significantly reduced the optical band gap of TiO2 from 3.22 to 2.86 eV. The photocatalytic performance of the synthesized TiO$_2$ catalysts was evaluated via methylene blue photodegradation, and all doped samples exhibited higher activity under visible light compared to pure TiO$_2$. The 5% Y/TiO$_2$ sample demonstrated the highest photocatalytic performance, achieving up to 91% methylene blue degradation and establishing it as the optimum doping level for enhanced activity.