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 similar to 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. (C) 2008 Elsevier B.V. All rights reserved.