Application of the LPE-Grown LuAG: Ce Film/YAG Crystal Composite Thermoluminescence Detector for Distinguishing the Components of the Mixed Radiation Field

Single-crystalline films (SCFs) of the LuAG: Ce garnet grown using the liquid-phase epitaxy method onto YAG single-crystal (SC) substrates were investigated for possible applications as composite thermoluminescent (TL) detectors. Such detectors may help to register the different components of ionizing radiation fields with various penetration depths, e.g., heavy charged particles and gamma or beta rays. It was found that the TL signal of LuAG: Ce SCF sufficiently differs from that of the YAG substrate concerning both the temperature and wavelength of emissions. Furthermore, even by analyzing TL glow curves, it was possible to distinguish the difference between weakly and deeply penetrating types of radiation. Within a test involving the exposure of detectors with the mixed alpha/beta radiations, the doses of both components were determined with an accuracy of a few percent

Luminescent properties of Gd14_{14}Lu0.1_{0.1}Y15_{15}Al5_5O12_{12}:Ce and Gd3_3Ga27_{27}Al2.3_{2.3}O12_{12}:Ce single crystals grown by micro-pulling down technique

The luminescent properties of the single crystals of Ce$^{3+}$ doped (Gd$_{1−x}$−yLuxYy)$_3$Al$_5$O$_{12}$:Ce (x = 0.1; y = 1.5) and Gd$_3$Ga$_x$Al$_{5-x}$O$_{12}$:Ce (x = 2.7) garnets (GLYAG:Ce and GGAG:Ce) were investigated in this work. Both crystals were grown by the micropulling down method. The conventional absorption and luminescence spectral measurements together with the luminescent spectroscopy under excitation by synchrotron radiation were performed to characterize the optical properties of crystals. It has been found that cumulative effects of reducing the ion radius from Gd$^{3+}$ to Y$^{3+}$ and Lu$^{3+}$ in the dodecahedral sites of the garnets host and alloying of Al$^{3+}$ ions in octahedral positions instead Ga$^{3+}$ ions increases the crystal field strength and causes the respective redshift of the Ce$^{3+}$ emission spectra in GLYAG:Ce crystals in comparison with GAGG:Ce garnet. The energy transfer from Gd$^{3+}$ cations to Ce$^{3+}$ has also been registered at the emission spectra and excitation spectra of both crystals. The energies of creation of the excitons bound with the Ce$^{3+}$ ions in GLYAG:Ce and GAGG:Ce hosts were found to be equal to 6.415 ± 0.15 eV and 6.22 ± 0.15 eV, respectively. Both crystals show well-distinguished thermo- and optically stimulated luminescence (TSL and IR OSL) after $α$- and $β$-particle irradiation. Meanwhile, GAGG:Ce crystals show significantly higher TSL and IR OSL intensities (by 3–4 times) and faster OSL decay kinetics in comparison with GLYAG:Ce counterpar

Ce³⁺ Doped Al₂O₃-YAG Eutectic as an Efficient Light Converter for White LEDs

Ce3+ doped Al2O3-YAG eutectics were successfully grown by the horizontal directional crystallization method. The crystallization rate of eutectic growth was changed in the 1–7.5 mm/h range at a growth temperature of 1835 ℃. The microstructure of eutectic samples was investigated using scanning electron microscopy and X-ray microtomography. The intrinsic morphology of eutectic represents the stripe-like channel structure with a random distribution of the garnet Y3Al5O12 (YAG) and Al2O3 (sapphire) phases. The content of these phases in the stripes changes in the 52.9–55.3% and 46.1–47.1% ratios, respectively, depending on the growth rate of the crystallization of the eutectic samples. The luminescent properties of the eutectic demonstrated the dominant Ce3+ luminescence in the garnet phase. The luminescence of the Ce3+ ions in Al2O3 has also been observed and the effective energy transfer processes between Ce3+ ions in the Al2O3 and YAG garnet phases were revealed under high-energy excitation and excitation in the UV Ce3+ absorption bands of sapphire. The phosphor conversion properties and the color characteristics (Al2O3-YAG):Ce eutectic with different thicknesses were investigated under excitation by a blue LED. We have also tested the prototypes of white LEDs, prepared using a blue 450 nm LED chip and (Al2O3-YAG):Ce eutectic photoconverters with 0.15 to 1 mm thicknesses. The results of the tests are promising and can be used for the creation of photoconverters for high-power white LEDs

Micropowder Ca2YMgScSi3O12:Ce Silicate Garnet as an Efficient Light Converter for White LEDs

This work is dedicated to the crystallization and luminescent properties of a prospective Ca2YMgScSi3O12:Ce (CYMSSG:Ce) micropowder (MP) phosphor converter (pc) for a white light–emitting LED (WLED). The set of MP samples was obtained by conventional solid-phase synthesis using different amounts of B2O3 flux in the 1–5 mole percentage range. The luminescent properties of the CYMSSG:Ce MPs were investigated at different Ce3+ concentrations in the 1–5 atomic percentage range. The formation of several Ce3+ multicenters in the CYMSSG:Ce MPs was detected in the emission and excitation spectra as well as the decay kinetics of the Ce3+ luminescence. The creation of the Ce3+ multicenters in CYMSSG:Ce garnet results from: (i) the substitution by the Ce3+ ions of the heterovalent Ca2+ and Y3+ cations in the dodecahedral position of the garnet host; (ii) the inhomogeneous local environment of the Ce3+ ions when the octahedral positions of the garnet are replaced by heterovalent Mg2+ and Sc3+ cations and the tetrahedral positions are replaced by Si4+ cations. The presence of Ce3+ multicenters significantly enhances the Ce3+ emission band in the red range in comparison with conventional YAG:Ce phosphor. Prototypes of the WLEDs were also created in this work by using CYMSSG:Ce MP films as phosphor converters. Furthermore, the dependence of the photoconversion properties on the layer thickness of the CYMSSG:Ce MP was studied as well. The changes in the MP layer thickness enable the tuning of the white light thons from cold white/daylight to neutral white. The obtained results are encouraging and can be useful for the development of a novel generation of pcs for WLEDs

Scintillation Characteristics of the Single-Crystalline Film and Composite Film-Crystal Scintillators Based on the Ce3^3+-Doped (Lu,Gd)3_3(Ga,Al)5_5O12_{12} Mixed Garnets under Alpha and Beta Particles, and Gamma Ray Excitations

The crystals of (Lu,Gd)3(Ga,Al)5O12 multicomponent garnets with high density ρ and effective atomic number Zeff are characterized by high scintillation efficiency and a light yield value up to 50,000 ph/MeV. During recent years, single-crystalline films and composite film/crystal scintillators were developed on the basis of these multicomponent garnets. These film/crystal composites are potentially applicable for particle identification by pulse shape discrimination due to the fact that α-particles excite only the film response, γ-radiation excites only the substrate response, and β-particles excite both to some extent. Here, we present new results regarding scintillating properties of selected (Lu,Gd)3(Ga,Al)5O12:Ce single-crystalline films under excitation by alpha and beta particles and gamma ray photons. We conclude that some of studied compositions are indeed suitable for testing in the proposed application, most notably Lu1.5Gd1.5Al3Ga2O12:Ce film on the GAGG:Ce substrate, exhibiting an α-particle-excited light yield of 1790–2720 ph/MeV and significantly different decay curves excited by α- and γ-radiation