Spectroscopic and crystal field study of Sm³⁺ in different phases of TiO₂

A systematic study of the photoluminescence spectra of samarium-doped crystalline TiO₂ was conducted within the temperature range 10-300 K in order to reveal the energy levels of the trivalent impurity ion in different phases of titania. The sol-gel route was used to prepare Sm-doped TiO ₂ powders. The nanocrystalline anatase phase was obtained by annealing up to 800 °C, whereas the rutile phase was developed by annealing above 1000 °C. Crystal field calculations of Sm³⁺ energy levels in the two phases of TiO₂ (anatase and rutile) were performed for the first time. The obtained set of energy levels assuming positioning of the Sm³⁺ ions in regular TiO₂ lattice sites was consistent with the experimental results. The effect of the different phases of titania on the impurity is discussed.