Search

Eu3+-doped GdAlO3 (Eu:GAP) and Gd0.5La0.5AlO3 (Eu:GLAP) perovskite single crystals were successfully grown using the optical floating zone (OFZ) method. The microstructure, optical, photoluminescence (PL) and radioluminescence (under X-ray excitation, XEL) were investigated. Under the PL excitation of 275 nm, obvious emission bands peaking at 556 nm, 592 nm, 617 nm, 625 nm, 655 nm, and 706 nm were demonstrated, which correspond to the 5D0 → 7Fj (j = 0–4) transitions of Eu3+. The grown Eu:GAP single crystal showed a stronger PL intensity compared with that of Eu:GLAP in the red light region. After annealing at 1000 °C for 4 h in weak reductive atmosphere (Ar + 5% H2), a slight redshift and dramatic enhancement of PL and XEL intensity occurred. In addition, Eu:GLAP show a more intense XEL emission than that of Eu:GAP. Considering their different densities, these two kinds of red luminescence phosphors are proposed to be promising in a wide field of X-ray imaging, warm white, or plant lighting, respectively. [ABSTRACT FROM AUTHOR]

Ce3+ doped Lu 3 Al 5 O 12 (Ce:LuAG) ceramics were fabricated by the solid-state reaction method through spark plasma sintering (SPS) from 1350 °C to 1700 °C for 5 min at a pressure of 50 MPa using micro powders. The average grain size of the SPSed ceramics gradually grew from 0.42 µm (1400 °C) to 1.55 µm (1700 °C), which is nearly one order of magnitude lower than that of vacuum sintered (VSed) Ce:LuAG ceramics (~24.6 µm). Characteristic Ce3+ emission peaking at around 510 nm appeared and 92% photoluminescence intensity of room temperature can be reserved at 200 °C revealing excellent thermal stability. The maximum radioluminescence intensity reached around 3 times of VSed Ce:LuAG ceramics and 7.8 times of BGO crystals. The maximum scintillation light yield under γ-ray (137Cs) excitation reached 9634 pho/MeV @ 2 μs. It is concluded that SPS technology is a feasible way to develop Ce:LuAG ceramics and further optical enhancement can be expected. [Display omitted] [ABSTRACT FROM AUTHOR]

The study deals with the use of different amounts of MgO or tetraethyl orthosilicate (C 8 H 20 O 4 Si, TEOS), from 0.04 wt %, 0.06 wt %, 0.08 wt %, 0.4 wt %, 0.6 wt % to 0.8 wt %, respectively, as additional sintering aids during the vacuum sintering of transparent Ce3+ doped Y 3 Al 5 O 12 (Ce:YAG) ceramics to investigate their effect on microstructure and luminescence properties. A comparative study was carried out by using X - ray diffraction, scanning electron microscopy/energy dispersive X - ray spectroscopy, optical and photo-luminesce spectra, as well as electroluminescent spectra. The dominant garnet phase was obtained even when adding 0.8 wt % of MgO or TEOS, while adding MgO led to finer average grain size (∼ 5 - 10 μm) and more homogenous distribution compared to TEOS (∼ 20 - 25 μm) in Ce:YAG ceramics. Adding a large amount of MgO was found to result in the segregation of MgO in Ce:YAG ceramics, while an excess of TEOS led to the segregation of Al 2 O 3. A strong absorption peak at 308 nm was observed in Ce:YAG ceramics with MgO sintering aids, which was ascribed to the existence of Ce4+ induced by a charge compensation effect of Mg2+. The optimum transmittance reached 80% @ 800 nm in Ce:YAG ceramics when adding 0.6 wt % TEOS, which also exhibited a maximum luminous efficacy of 106 lm/W. Si4+ was experimentally proved to have a better optimization effect on luminous efficacy compared to Mg2+. • MgO or TEOS (C 8 H 20 O 4 Si) was added as additional sintering aids in a wide amount range. • MgO proves to have distinct inhibit effect on the grain growth. • Better luminous efficacy were observed in ceramics with TEOS additives. [ABSTRACT FROM AUTHOR]