Recent progress in advanced optical materials based on gadolinium aluminate garnet (Gd 3 Al 5 O 12 ) (original) (raw)
Related papers
Science and Technology of Advanced Materials, 2012
The metastable garnet lattice of Gd 3 Al 5 O 12 is stabilized by doping with smaller Lu 3+ , which then allows an effective incorporation of larger Eu 3+ activators. The [(Gd 1−x Lu x) 1−y Eu y ] 3 Al 5 O 12 (x = 0.1-0.5, y = 0.01-0.09) garnet solid solutions, calcined from their precursors synthesized via carbonate coprecipitation, exhibit strong luminescence at 591 nm (the 5 D 0 → 7 F 1 magnetic dipole transition of Eu 3+) upon UV excitation into the charge transfer band (CTB) at ∼239 nm, with CIE chromaticity coordinates of x = 0.620 and y = 0.380 (orange-red). The quenching concentration of Eu 3+ was estimated at ∼5 at.% (y = 0.05), and the quenching was attributed to exchange interactions. Partial replacement of Gd 3+ with Lu 3+ up to 50 at.% (x = 0.5) while keeping Eu 3+ at the optimal content of 5 at.% does not significantly alter the peak positions of the CTB and 5 D 0 → 7 F 1 emission bands but slightly weakens both bands owing to the higher electronegativity of Lu 3+. The effects of processing temperature (1000-1500 • C) and Lu/Eu contents on the intensity, quantum efficiency, lifetime and asymmetry factor of luminescence were thoroughly investigated. The [(Gd 0.7 Lu 0.3) 0.95 Eu 0.05 ] 3 Al 5 O 12 phosphor processed at 1500 • C exhibits a high internal quantum efficiency of ∼83.2% under 239 nm excitation, which, in combination with the high theoretical density, favors its use as a new type of photoluminescent and scintillation material.
Luminescence and Luminescence Quenching in Gd3(Ga,Al)5O12 Scintillators Doped with Ce3+
The Journal of Physical Chemistry A, 2013
The optical properties of gadolinium gallium aluminum garnet, Gd 3 (Ga,Al) 5 O 12 , 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 Munõz-García et al. (Munõz-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 Gd 3 (Ga,Al) 5 O 12 with 40% of Al 3+ replaced by Ga 3+ .
Crystal growth and luminescence properties of calcium- and vanadium-doped gadolinium gallium garnet
Chemical Physics Letters, 1991
1-mol%-Yb-doped Gd 3 Al 2 Ga 3 O 12 infra-red scintillator crystal has been studied as a novel implantable radiation monitor in radiation therapy. Powder X-ray diffraction measurement and chemical analysis with a field emission scanning microscope and wavelength dispersive spectrometer determined its garnet structure and average chemical composition of Yb 0.03±0.01 Gd 2.99±0.07 Al 2.21±0.08 Ga 2.64±0.09 O 12.10±0.09. Transmittance measurements reached high values of approximately 70% in the human body transparency region between 650 to 1200 nm. Photoluminescence peaks were detected around 970 and 1030 nm under the 940 nm excitation with a Xe lamp. Infra-red scintillation emissions were clearly observed around 970 and 1030 nm due to Yb 3+ 4f-4f transitions under X-ray excitation. Therefore, these results suggest that Yb-doped Gd 3 Al 2 Ga 3 O 12 might be used as an infra-red scintillator material.
Journal of Luminescence, 2016
Cerium-doped lutetium aluminum garnet (LuAG:Ce) and yttrium aluminum garnet (YAG:Ce) transparent ceramics of same dimension were fabricated and their optical and scintillation properties were studied. LuAG:Ce transparent ceramic showed higher light yield under UV and X-ray excitation with respect to YAG:Ce transparent ceramic. YAG:Ce transparent ceramic showed higher light yield under gamma excitation and better energy resolution, which could be due to the considerable amount of slower emission (38.5%) in LuAG:Ce as well as lower optical transparency with respect to YAG:Ce ceramic.
Luminescence properties of Eu3+ doped gadolinium aluminum garnet phosphors
Optik, 2020
Gd 3 Al 5 O 12 (GdAG) doped with Eu (Gd 1-x AG: Eu x) was synthesized by using sol gel method with the doping concentration of Eu as 0.1, 0.5 and 1.0 mol%. The prepared material was sintered at 1100°C.GdAG was doped with to check its utility as material for the white light emission. The synthesized material was characterized by using XRD, FT-IR and Fluorescence spectroscopy. XRD analysis revealed that crystal phase remained same and there was no change in the crystallite size on doping. XRD results were supported by FTIR spectra. The formation of metal oxygen bonds were confirmed by multiple absorption peaks in the range 400-740 cm −1 in FT-IR spectrum. Florescence spectra show the broad emissions in the visible region showing Eu doped GdAG as a good alternative phosphor for white light source.
Journal of Luminescence, 2016
Crystal growth by micro-pulling-down, Czochralski, and floating zone methods and scintillation properties of Ce:Gd3(Ga,Al)5O12 (Ce:GGAG) multi-component oxide garnets, and Ce:Gd2Si2O7 (Ce:GPS) or Ce:(La,Gd)2Si2O7 (Ce:La-GPS) pyro-silicates are reviewed. GGAG crystals demonstrated practically linear dependences of some of the parameters including lattice constant, emission wavelength, and band gap on Ga content. However, emission intensity, light yield and energy resolution showed maxima for intermediate compositions. GGAG crystals had highest light yield of 56,000photon/MeV for Ga content of 2.7 atoms per garnet formula unit. Similarly the light yield and energy resolution of La-GPS showed the highest values of 40,000 photon/MeV and 4.4%@662keV, respectively, for La-GPS containing 10% of La. Moreover, La-GPS demonstrated stable scintillation performance up to 200°C.
Czochralski growth of Gd3(Al5−xGax)O12 (GAGG) single crystals and their scintillation properties
Journal of Crystal Growth, 2014
Ce:Gd 3 (Al x Ga 1-x) 5 O 12 (x=2.5/5 and 3/5, Ce:GAGG-2.5 and Ce:GAGG-3) crystals were grown by the Czochralski process in order to reduce cost of the starting materials as compared with conventional Ce:Gd 3 Al 2 Ga 3 O 12 (Ce:GAGG-2) crystal which have high light output. Although perovskite phase was detected in Ce:GAGG-3, Ce:GAGG-2.5 had single-phase garnet structure. Solidification fraction for the Ce:GAGG-2.5 growth was 0.52. Optical properties including transmittance, emission, and excitation spectra of 30 samples cut from the Ce:GAGG-2.5 bulk ingot did not depend on their original position along the growth axis. These samples had light outputs of approximately 58,000 ± 3,000 photons/MeV. However, scintillation decay times varied from 140 to 200 ns and depended on the position clearly.
Optical Materials, 2017
The luminescence and scintillation properties of the gadolinium yttrium aluminium garnets, (Gd,Y) 3 Al 5 O 12 doped with Ce 3þ are investigated as a function of the Gd/Y ratio with the aim of an improved understanding of the luminescence quenching, energy transfer and phase stability in these materials. An increase of both crystal field strength and instability of the garnet phase with increasing content of Gd 3þ is observed. The instability of the garnet phase results in an appearance of the perovskite phase inclusions incorporated into the garnet phase. The luminescence features of Ce 3þ in the perovskite phase inclusions and in the main garnet phase are studied separately. The thermal quenching of the 5 d / 4f emission of Ce 3þ in the latter phase is determined by temperature dependence of the photoluminescence decay time. The results show that the onset of the thermal quenching is moved to lower temperatures with increasing gadolinium content. The measurements of temperature dependence of delayed radiative recombination do not reveal a clear evidence that the thermal quenching is caused by thermally induced ionization of the Ce 3þ 5d 1 excited state. Therefore, the main mechanism responsible for the luminescence quenching is due to the non-radiative relaxation from 5d 1 excited state to 4f ground state of Ce 3þ. The energy transfer processes between Gd 3þ and Ce 3þ as well as between perovskite and garnet phases are evidenced by the photoluminescence excitation and emission spectra as well as decay kinetic measurements. Thermally stimulated luminescence (TSL) studies in the temperature range 77 e497 K and scintillation decays under g excitation complete the material characterization.