Luminescence and Luminescence Quenching in Gd₃(Ga,Al)₅O₁₂ Scintillators Doped with Ce³⁺

Abstract

The optical properties of gadolinium gallium aluminum garnet, Gd3(Ga,Al)5O12, doped with Ce(3+) are investigated as a function of the Ga/Al ratio, aimed at an improved understanding of the energy flow and luminescence quenching in these materials. A decrease of both the crystal field strength and band gap with increasing content of Ga(3+) is observed and explained by the geometrical influence of Ga(3+) on the crystal field splitting of the 5d level in line with theoretical work of Muñoz-García et al. ( uñoz-García, A. B.; Seijo, L. Phys. Rev. B 2010, 82, 184118 ). Thermal quenching results in shorter decay times as well as reduced emission intensities for all samples in the temperature range from 100 to 500 K. An activation energy for emission quenching is calculated from the data. The band gap of the host is measured upon Ga substitution and the decrease in band gap is related to Ga(3+) substitution into tetrahedral sites after all octahedral sites are occupied in the garnet material. Based on the change in band gap and crystal field splitting, band diagrams can be constructed explaining the low thermal quenching temperatures in the samples with high Ga content. The highest luminescence intensity is found for Gd3(Ga,Al)5O12 with 40% of Al(3+) replaced by Ga(3+).

Origin of improved scintillation efficiency in (Lu,Gd)3(Ga,Al)5O12:Ce multicomponent garnets: An X-ray absorption near edge spectroscopy study

“…The optimum composition, Gd 3 Ga 2 Al 3 O 12 :Ce, is in accordance with the result reported in Ref. 35 and close to that of single crystal. 23 So far, as discussed above, there are two reasonable explanations: (i) "band-gap engineering" 15,16 -after partial Ga 3+ admixture, shallow traps formed by antisite defects and some deeper traps caused by impurities or host lattices can be buried in the lowering conduction band suppressing defect-trapping effect; (ii) "energy level positioning" strategy 19, 23 -Gd 3+ admixture secures the energy separation between CB and 5d 1 of Ce 3+ avoiding/diminishing thermally induced ionization around room temperature.…”

Comparative study of optical and scintillation properties of Ce:YAGG, Ce:GAGG and Ce:LuAGG transparent ceramics

“…This is because the non-radiative rate by thermal ionization increases due to the small energy gap between the 5d 1 and CB. 28) Figure 5 shows the radioluminescence spectra of Ce:YAGG, Ce:GAGG and Ce:LuAGG. As seen in the PL spectra, these ceramics also exhibited a single broad emission in the wavelength range from 470 to 600 nm.…”

Thermal ionization and thermally activated crossover quenching processes for5d−4fluminescence inY3AlUeda1, Meijerink2, Dorenbos3 et al. 2017Phys. Rev. BSelf Cite752420View full textAdd to dashboardCite

“…However, in the 1990s, Yen et al demonstrated the existence of thermally activated ionization (thermal ionization) quenching from the Ce 3+ : 5d excited level in some compounds by photoconductivity analysis [2]. Since then both mechanisms are often discussed as being responsible for thermal quenching of luminescence in white LEDs phosphors [3][4][5][6][7]. However, the mechanism proposed is not always supported by the experimental results.…”

“…To provide a better understanding of the quenching processes of the 5d-4f luminescence, the family of garnet Ln 3 M 5 O 12 (Ln = Gd, Y, Lu; M = Sc, Al, Ga) doped with Ce 3+ and Pr 3+ serve as important model systems because of the possibility to tune optical properties as a function of covalency, size of the cation site, bandgap, vibrational energies, etc., by variation of the ions on the three different cation sites in the garnet hosts [5,[10][11][12][13]. In the past, we have focused on the garnet materials doped with Ce 3+ for the analysis of the quenching mechanisms and for the development of persistent phosphors [14][15][16][17] (LuAG), precise configuration coordinate diagrams were constructed from low-temperature spectroscopy data and the 5d-4f thermal quenching behavior was related to the energy gap between the lowest 5d 1 state and the next lower 4f state [10].…”