Lu3Al5O12 Garnet Research Articles

Investigation of X-rays Beams Uniformity in Radiotherapeutic Tumor Treatment Procedure Using LuAG:Ce Crystal Detectors.

In this study, Ce3+-doped Lu3Al5O12 garnet (LuAG) crystal detectors, with a density of ρ = 6 g/cm3 and an effective atomic number Zeff = 62, are proposed as promising materials for radiotherapy applications. This type of detector demonstrates excellent uniformity of structural and optical properties, high thermoluminescence (TL) light yield, optimal position of main TL glow peaks at temperatures around 245-295 °C, and high radiation stability. The set of TL detectors made from LuAG:Ce single crystal was used to evaluate the uniformity of dose and energy spectra of X-ray radiation from a clinical accelerator with 6 MV and 15 MV beams at the Department of Medical Physics, Oncology Center in Bydgoszcz, Poland, and γ-rays from a 60Co source at the National Institute of Oncology in Warsaw. The LuAG:Ce crystal detectors demonstrated highly promising results for registering X-ray radiation from accelerators with both 6 MV and 15 MV electron beams, as well as γ-rays from a 60Co source with energies of 1.17 and 1.33 MeV.

Engineering atomic size mismatch in Pr3+, La3+ codoped Lu3Al5O12 garnet single crystals for tailored structure and functional properties

This study provided the first in-depth investigation of the effects of large dopant incompatibility (Pr3+ and La3+ ions) on the small host lattice element (Lu3+) in Lu3Al5O12 (LuAG) single crystal. The growth of such complex crystals from the melt presented many challenges. By engineering the ionic radius ratio of RE- and M-site cations, a single-crystal phase stabilized by configurational entropy was achieved. This investigation elucidated the crystallization behavior of configurationally disordered rare-earth aluminum garnet oxide (Lu1−x−yPrxLay)3Al5O12 from the melt and characterized its functional properties, including microstructural, optical, photoluminescence, and scintillation properties, between 5 and 300 K. Relaxation of the imposed strain energy led to local perturbations and destabilization of the garnet structure. Multielemental EDS mapping, micro-Raman spectroscopy, and thermoluminescence revealed the mechanism by which atomic size mismatch drove a smooth transition from the garnet to the perovskite phase in high entropy garnets. The optical, photoluminescence, and scintillation measurements provided fundamental insights into property changes driven by incompatibility doping. Standard and modified Judd-Ofelt theory analysis of absorption spectra determined the phenomenological Judd-Ofelt parameters Ωλ and radiative lifetimes. Atomic size mismatch engineering offers a promising approach to overcoming the limitations of conventional eutectic synthesis methods.

Red-tunable LuAG garnet phosphors via Eu3+→Mn4+ energy transfer for optical thermometry sensor application

The Eu3+→Mn4+ energy transfer strategy is designed in the Lu3Al5O12 garnet structure to achieve color-adjustable narrow emission from orangish-red to deep-red light and remarkable thermal quenching improvement for optical thermometry sensors.

Liquid phase epitaxy growth of high-performance composite scintillators based on single crystalline films and crystals of LuAG

Top – Scheme of the composite scintillator for registration of α-particles and γ-quanta. Bottom – Samples of the LuAG:Ce SCF/LuAG:Sc SC (a) and LuAG:Pr SCF/LuAG:Sc SC (b) composite scintillators prepared using the liquid phase epitaxy growth method.

Comparison of the luminescent properties of LuAG:Pr nanopowders, crystals and films using synchrotron radiation

Comparison of the luminescent properties of nanopowder, single crystal and single crystalline film of Pr3+ doped Pr-doped Lu3Al5O12 garnet (LuAG:Pr) prepared by the different technological methods is performed in this work using the time-resolved emission spectroscopy under excitation by synchrotron radiation with an energy of 3.7–25 eV at 300 K and 10 K. The notable differences in the properties of the Pr3+ luminescence are observed in LuAG:Pr crystals and films caused by involving the LuAl antisite defects and oxygen vacancies in crystals and Pb2+ flux related dopant in films in the excitation processes of the Pr3+ luminescence. At the same time, we have also found that the influence of host defects on the Pr3+ luminescence is significantly smaller in the LuAG:Pr nanopowders.

Effect of Y3+ substitution on structural and photoluminescence properties of solid solutions [(Lu1−xYx)1−z Cez]3Al5O12 phosphors

Cerium activated Lu3Al5O12 garnet, efficiently substituted by Y3+ doping, and has been developed for green-yellow emitting phosphors. The powder processing of [(Lu1−xYx)1−z Cez]3Al5O12 solid solution powder were achieved through synthesis via sol–gel method. The Y3+ cationic substitutions in the LuAG host matrix have been changed from 0.05 to 0.2 at%, and their effects on structural and luminescence properties were systematically investigated. The phase formation and characteristics of solid solution were studied by means of differential scanning calorimetry (DSC), X-ray diffraction technique (XRD), Fourier transforms infrared spectroscopy (FTIR) and photoluminescence spectroscopy (PL). The DSC result shows that the crystallization of the powder precursors started at 960 °C. X-ray diffraction analysis indicated that the single and pure cubic crystalline phase was formed and no secondary phases of the garnet structure are observed. The photoluminescence spectra of these solid solutions exhibit band edge emission at 500 nm in green-yellow region attributed to the interconfigurational 5d → 4f transitions of Ce3+ ions. Additionally, the evolution of crystallite size and photoluminescence spectra with the increasing of Y3+ content is studied and discussed.

The effect of Ga‐doping on the defect chemistry of RE3Al5O12 garnets

AbstractIt has been recently shown that the addition of Ga to Lu3Al5O12 garnet (LuAG) removes the electron trapping associated with cation antisite defects. In this paper, we show via atomic scale simulations that the replacement of Al with Ga in LuAG actually lowers the energy of the antisite disorder process. Thus, we predict that Ga additions will lead to an increase of the antisite defect concentration and, in the absence of the electronic structure changes, would actually degrade the performance of the material. Since there are two crystallographically distinct Al sites in the garnet structure, we not only present results for complete replacement of Al with Ga, but also partial replacement for 40% (on 16a) and 60% (on 24d) of the Al with Ga. Our results support the explanation for Ga‐doping leading to improvement in garnet scintillator performance that relies on variations of the electronic structure rather than reduction of the antisite defect concentration. magnified imageCation antisite defects in RE3Al5O12 garnet, where small light gray atoms and large dark gray atoms are lattice Al and RE atoms, respectively. The constituents of the antisite defect pairs are labeled, and it should be noted that the Ga atom (blue) is similar in size to RE (green). Oxygen atoms are not shown for clarity.

ChemInform Abstract: Rapid Microwave Preparation of Highly Efficient Ce3+‐Substituted Garnet Phosphors for Solid State White Lighting.

AbstractCe‐substituted Y3Al5O12 and Lu3Al5O12 garnet phosphors are prepared by microwave heating of mixtures of Y2O3 or Lu2O3, Al2O3, CeO2, and small amounts of NH4F as flux using mixtures of granular and powdered carbon as microwave susceptor.

Time‐resolved spectroscopy of exciton‐related states in single crystals and single crystalline films of Lu3Al5O12 and Lu3Al5O12:Ce

AbstractTime‐resolved excitation spectra were measured at the same conditions at 10 K in the 4–20 eV energy range for the luminescence of self‐trapped and various localized excitons as well as of Ce3+‐, Pb2+‐, and Bi3+‐related centers in single crystals and single crystalline films of Lu3Al5O12 garnet. The decay kinetics of the intrinsic 4.9 and 3.65 eV luminescence of Lu3Al5O12 crystals were studied at 4.2–300 K in the 10−9–10−3 s time range. The origin and structure of the exciton states as well as the luminescence, energy transfer, and recombination processes, taking place under excitation in the exciton absorption region, were discussed. The influence of various defects on the scintillation characteristics of Ce3+‐ and Pr3+‐doped Lu3Al5O12 crystals was considered.

Growth and scintillation properties of Sc, Pr, Ce co-doped LuAG epitaxial garnet layers

Single crystalline Sc, Pr, Ce co-doped Lu3Al5O12 garnet layers were grown by liquid phase epitaxy. The Sc doping increases the scintillation response of Pr3+ activator ions because of overlap of the Sc-related emission around 275 nm with the 4f→5d absorption band of Pr3+ centers. The radioluminescence (RL) spectra give evidence for presumed energy transfer form Sc3+ to Pr3+ activator ions. Significant increase of the RL emission output was observed when co-doping with both Pr and Sc ions compared to Sc-free samples. The maximum integral RL was noticed for samples with relatively high Sc concentration, 1.2 - 3 at %. On the contrary, an increase of the photoelectron yield, Nphe, measured under alpha particle excitation, was observed only for rather low Sc content, ∼0.6 at %, at higher Sc concentrations Nphe decreased. Nevertheless, LuAG epitaxial layers with optimal Sc and Pr contents show comparable or even a bit higher Nphe yield and energy resolution than Cz-grown Pr:LuAG single crystals. Furthermore, the slow components in photoelectron response were significantly suppressed in epitaxial layers compared to single crystals.