|
The structural and luminescent results of nondoped, terbium and dysprosium doped, and codoped Y2O3 powders are presented. Different percentages of the rare earth ions were employed. The powders were obtained by means of the solvent evaporation technique and were annealed at 1100°C for 2 h. The emission spectra of these samples are associated with the characteristic intraelectronic energy levels that are related to the Tb3 + and Dy3 + ions transitions. The maximum peaks of emission are located at 542 nm with λexc = 274 nm for terbium that is associated with the D54 to F75 transition; for dysprosium, the maximum is at 573 nm, when excited with λexc = 210 nm, corresponding to the F49 / 2 to H613 / 2 transition; the emission spectra of the Y2O3 : Tb4 % : Dy3 % and Y2O3 : Tb4 % : Dy0.75 % phosphors were also obtained, and the emissions of these two ions are observed when excited with λexc = 260 nm, suggesting that these ions are near neighbors, giving place to energy transfer between these two ions. When the sample of Y2O3 : Tb3 + is excited with λexc = 274 nm, a single exponential decay is observed with τ = 2.95 ms; when the Y2O3 : Dy3 + is excited with λexc = 210 nm, there is decay time with τ = 0.89 ms; and when excited with λexc = 274 nm, the phosphors of Y2O3 : Tb3 + : Dy3 + also have a single exponential decay with τ = 2.04 ms. The Commission Internationale de l’Eclairage diagram coordinates obtained for different relative contents of these lanthanide ions are given. X-ray diffraction analyses of these phosphors indicate a polycrystalline cubic yttrium oxide structure with a grain size running from 37 to 45 nm.
|
