Synthesis, characterization, thermo- and photoluminescence properties of Bi3+ co-doped Gd2O3:Eu3+ nanophosphors

Gd 2 O 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 5 D 0 → 7 F 0 , 5 D 0 → 7 F 2 and 5 D 0 → 7 F 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 2 O 3 :Eu 3+ exhibited a dosimetrically useful glow peak at 380°C. Using thermoluminescence glow peaks, the trap parameters have been evaluated and discussed. The observed emission characteristics and energy transfer indicate that Gd 2 O 3 :Eu 3+ , Bi 3+ phosphors have promising applications in solid-state lighting.