Sol–gel preparation and luminescent properties of CeO 2:Ln (Ln = Eu 3+ and Sm 3+) thin films

Abstract

New transparent CeO 2:Ln (Ln = Eu 3+ or Sm 3+) thin-film phosphors have been fabricated by a sol–gel method. The CeO 2:Ln films with the Ln concentrations of 1 at.% showed the strongest photoluminescence (PL) upon ultraviolet (UV) light excitation. At higher Ln concentrations, the PL intensity decreased because of the nonradiative energy transfer. For Eu 3+ ions doped in the CeO 2 lattice with inversion symmetry, an orangey red emission due to a magnetic-dipole 5 D 0 → 7 F 1 transition (591 nm) was dominant when excited at a wavelength of 340 nm. In contrast, much stronger orange emissions (573 nm) due to 4 G 5/2 → 6 H 5/2 were observed for Sm 3+ ions. Apparently, the Eu 3+ and the Sm 3+ ions had different efficiencies of the excitation through the energy transfer from the “Ce 4+–O 2−” charge transfer state induced by the UV irradiation.