Influence of Al Doping on Structure, Morphology and Optical Properties of TiO2 Nanoparticles
DOI:
https://doi.org/10.15407/ujpe71.10.824Keywords:
titanium dioxide (TiO2), nanoparticles, Al3+ -doping, crystal structure, optical propertiesAbstract
Titanium dioxide (TiO2) nanoparticles, both undoped and heterovalently substituted with aluminum ions, were synthesized using sol–gel routes. The influence of synthesis parameters, annealing temperature (500–900°C), and Al3+ doping concentration on the phase composition, crystallographic parameters, crystallite size, defect structure, and optical properties of TiO2 was systematically investigated. X-ray diffraction analysis revealed a temperature-driven anatase-to-rutile phase transformation in undoped TiO2, while aluminum incorporation stabilized the anatase phase at moderate temperatures and suppressed rutile formation. At elevated temperatures and high dopant concentrations, a solubility limit of Al3+ in the TiO2 lattice was observed, leading to the formation of secondary α-Al2O3 phases. Crystallite size analysis showed that increasing annealing temperature promotes grain growth and reduces lattice defect density, whereas Al3+ doping inhibits crystallite growth in anatase and increases defect concentration. In contrast, for rutile TiO2 at high temperatures, aluminum incorporation enhances crystallite growth and lattice ordering. Photoluminescence studies demonstrated weak intrinsic emission of TiO2 governed by defect-related states, with emission bands attributed to surface states, oxygen vacancies, and Ti3+ centers. Highly Al3+-doped samples exhibited additional red and near-infrared emission bands, which were assigned to trace Cr3+ impurities unintentionally introduced with aluminum precursors. The results demonstrate that synthesis conditions and heterovalent substitution provide effective tools for tuning the structural, morphological, and optical properties of TiO2 nanoparticles. The findings highlight the critical role of defect chemistry, phase composition, and impurity-related effects in tailoring TiO2-based materials for UV-blocking, cosmetic, and photonic applications.
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