Effect of Laser Pre- Treatment on the Sintering Dynamics of TiO2 Nanopowder

Titanium dioxide (TiO₂) is widely used in photocatalysis, sensing, and energy applications; however, conventional sintering typically requires high temperatures, leading to grain coarsening, residual porosity, and undesired phase transformations. In this work, femtosecond (fs), nanosecond (ns), and continuous-wave (CW) laser pre-treatments were employed to tailor the microstructural evolution of TiO₂ nanopowders prior to furnace sintering and to regulate subsequent diffusion pathways.

Femtosecond laser irradiation generated a high density of nonequilibrium oxygen vacancies, forming defect clusters that act as fast pipe-diffusion channels. This vacancy-assisted transport significantly enhanced atomic mobility, enabling rapid densification at a reduced temperature of 550 °C within 10 min, while promoting pronounced neck growth, reduced porosity, and increased hardness.

Nanosecond laser treatment induced moderate defect formation and dangling bonds, which facilitated in-situ ultrafine grain formation and activated grain-boundary diffusion, resulting in improved densification at 650 °C after 4 h of sintering. In contrast, CW laser irradiation predominantly caused thermal annealing with minimal defect generation, leading to negligible changes in diffusion behavior and sintering response.

These results demonstrate that laser-induced defect engineering effectively governs diffusion mechanisms prior to thermal processing, enabling low-temperature densification of TiO₂ while preserving the anatase phase and enhancing processing efficiency for advanced functional oxide applications.

Keywords: TiO₂ sintering; femtosecond laser; nanosecond laser; diffusion mechanisms; oxygen vacancies; defect engineering