Luminescence properties of sol–gel-derived TiO2:Sm powder

Sm-doped TiO2 nanopowder phosphors were prepared by employing a sol–gel route. Thermal treatment crystallizes the powder in anatase phase and leads to a quite efficient (quantum yield ∼15%) Sm3+ luminescence with a well-resolved fine structure under optical excitation within the fundamental absorption band of the host. From the PL spectrum and its temperature dependence the energy level scheme of Sm3+ in crystalline powder of anatase was obtained and analyzed based on symmetry considerations. In the case of host-mediated excitation we found a relatively long-lasting afterglow of Sm3+ emission characterized by a nearly power-law kinetics. The overall intensity of Sm3+ emission increased with temperature. The origin of the behavior, connected to the migration and relaxation of host electronic excitations, are discussed.