AVS 57th International Symposium & Exhibition
    Actinides and Rare Earths Topical Conference Tuesday Sessions
       Session AC-TuA

Paper AC-TuA1
Enhanced Photoluminescence from Europium-Doped Gadolinium-Based Nanocrystal Scintillators

Tuesday, October 19, 2010, 2:00 pm, Room Isleta

Session: Science and Technology of Actinides and Rare Earths
Presenter: T.-K. Tseng, University of Florida
Authors: T.-K. Tseng, University of Florida
J. Choi, University of Florida
M.R. Davidson, University of Florida
P.H. Holloway, University of Florida
Correspondent: Click to Email
Scintillator crystals have traditionally been grown with complex single crystal methods such as Czochralski and Bridgman techniques, which frequently result in high costs and small crystal size. Therefore, development of processes for larger area, polycrystalline ceramic scintillators with high luminescence is of great interest due to their potential for mass production, versatility in shape and size, and low cost. In this study, spherical Gd2O3:Eu3+ and almond-like GdVO4:Eu3+ nanocrystals were synthesized using a water-based solution precipitation method at low reaction temperatures (<90 ℃) in short times (3 min~1 h). Core/Shell nanostructures with mono-dispersed 220 nm SiO2 cores and an ~13 nm Gd2O3 shell, i.e. SiO2/Gd2O3:Eu3+, were prepared. With an additional un-doped Gd2O3 shell to form a SiO2/Gd2O3:Eu3+/Gd2O3 nanostructure, the quantum yield was 28% higher than that of SiO2/Gd2O3:Eu3+. This enhanced photoluminescence (PL) is attributed to a Gd2O3 surface shell serving (i) as a sensitizer with energy transfer to the Eu3+ in the Gd2O3:Eu3+ shell, plus (ii) passivation of non-radiative surface quenching sites. Enhanced PL was also demonstrated from polyol-synthesized Gd2O3:Eu3+/Y2O3 nanocrystals. Increased PL can also be achieved by incorporating Bi3+ sensitizer ions into colloidal GdVO4:Eu3+ nanocrystals which were self-assembled into almond-like clusters composed of ~60 nm nanorods. With 2% Bi3+ co-doped in GdVO4:Eu3+ nanocrystals, PL was enhanced by 45%, 90% and 570% when excited by 280, 323 and 347 nm photons, respectively. This enhancement is attributed to increased absorption from Bi-O bonds, plus extension of the excitation band edge to longer wavelength. For Bi3+ ion concentrations >10%, PL from co-doped nanocrystals decreased due to non-radiative decay from Bi3+-induced trapping centers, as well as increased Bi3+-Bi3+ energy transfer instead of Bi3+-Eu3+ transfer.