Synthesis, characterization, thermo- and photoluminescence properties of Bi~(3+) co-doped Gd_2O_3:Eu~(3+) nanophosphors

摘要

Gd_2O_3:Eu~(3+) (4 mol%) co-doped with Bi~(3+) (Bi = 0, 1, 3, 5, 7, 9 and 11 mol%) ions were synthesized by a low-temperature solution combustion method. The powders were calcined at 800°C and were characterized by powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), Fourier transform infrared and UV-Vis spectroscopy. The PXRD profiles confirm that the calcined products were in monoclinic with little cubic phases. The particle sizes were estimated using Scherrer's method and Williamson-Hall plots and are found to be in the ranges 40-60 nm and 30-80 nm, respectively. The results are in good agreement with TEM results. The photoluminescence spectra of the synthesized phosphors excited with 230 nm show emission peaks at -590, 612 and 625 nm, which are due to the transitions ~5D_0 →~7F_0, ~5D_0 →~7F_2 and ~5D_0 → ~7F_3 of Eu~(3+), respectively. It is observed that a significant quenching of Eu~(3+) emission was observed under 230 nm excitation when Bi~(3+) was co-doped. On the other hand, upon 350 nm excitation, the luminescent intensity of Eu~(3+) ions was enhanced by incorporation of Bi~(3+) (5 mol%) ions. The introduction of Bi~(3+) ions broadened the excitation band of Eu~(3+) of which a new strong band occurred ranging from 320 to 380 nm. This has been attributed to the 6s~2 → 6s6p transition of Bi~(3+) ions, implying a very efficient energy transfer from Bi~(3+) ions to Eu~(3+) ions. The gamma radiation response of Gd_2O_3:Eu~(3+) exhibited a dosimetrically useful glow peak at 380℃. Using thermoluminescence glow peaks, the trap parameters have been evaluated and discussed. The observed emission characteristics and energy transfer indicate that Gd_2O_3:Eu~(3+), Bi~(3+) phosphors have promising applications in solid-state lighting.