X-ray Excited Luminescence Spectra Research Articles

Scintillation and photoluminescence performance of Ce3+-doped high gadolinium oxyfluoride glass for circular electron-positron collider (CEPC)

The large size (4 cm × 4 cm × 1 cm) Ce3+-doped high gadolinium oxyfluoride glass with density of 5.83 g/cm³ was prepared by the melt quench method at 1220 °C. The glass is colorless and transparent over the visible range. The prolonged decay time under 275 nm UV light demonstrates the energy transfer from Gd3+ ions to Ce3+ ions. The X-ray excited luminescence spectra (XEL) show the emission peak corresponds to the 5d→4f transitions of Ce3+ ion. The integral emission intensity of glass was compared with that of bismuth germanate oxide (BGO) crystals. The scintillation property of glass was studied under the γ-ray from 137Cs source and a clear energy peak was observed with light yield (LY) over 1100 ph/MeV. The scintillation decay time comprises fast and slow components. All results presented in this work indicate the appropriate potential to be high-energy rays detecting material for CEPC.

Luminescence properties of Er3+ doped high density germanate glass scintillators for X-ray computed tomography (CT)

Er3+ doped high density germanate glasses with compositions of 50GeO2-10BaO–10Al2O3-15Lu2O3-(15-x) La2O3-xEr2O3 (x = 0, 0.1, 0.5, 1.0, 1.5, and 2.0, in mol%) have been prepared by the melt-quenching method. The optical and physical properties of the samples were characterized by differential scanning calorimetry (DSC), density, transmittance spectra, photoluminescence (PL) spectra, and X-ray excited luminescence (XEL) spectra. The densities were in the range from 5.90 to 6.07 g/cm3. The strong green emissions around 552 nm of Er3+ were observed upon the excitations of 378 nm light and the X-ray, and the lifetimes of 552 nm emission were in the range of 20.88–96.47 μs. The results show that Er3+ doped high density germanate glasses could be used as potential scintillators for X-ray CT.

Preparation and optical properties of high-quality green cobalt sapphires

A series of (Al2O3)100-x(Co3O4)x (x = 0, 0.04, 0.1, 0.2, 0.3, 0.4) single crystals were successfully prepared by the optical floating zone method for the first time, even though natural cobalt-containing sapphires have not been observed. It has been found that the (Al2O3)99.70(Co3O4)0.30 single crystal is a high-quality, beautiful, and stable green cobalt sapphire like an emerald, and its density is 3.984 g/cm3. XRD and Raman spectra of the (Al2O3)100-x(Co3O4)x crystals show that cobalt is successfully incorporated in the Al2O3 which retains its hexagonal structure. Two strong broad absorption peaks at 436 nm and 652 nm were observed in the UV–Vis absorption spectra, which are assigned to the 1A1→1T1 and 1A1→1T2 transitions of Co3+, respectively. Whilst the optical band gaps were in the range 4.43–3.95 eV. Under excitation at 436 nm, one strong emission peak at 864 nm and a weak emission peak at 692 nm were found in the photoluminescence (PL) spectra of the cobalt sapphires. At Co3O4 concentrations lower than 0.30 mol%, the intensities of both emission peaks increase with Co3O4 concentration, and reach their maxima at 0.30 mol%, then decrease with the further increases in Co3O4. Also, X-ray excited luminescence (XEL) spectra show that the cobalt sapphires have a high sensitivity for X-ray detection. Overall, cobalt sapphires can have various potential uses, such as in jewelry, as ultraviolet detectors, in X-ray detection, and in near-infrared emission devices.

Luminescence properties of CsPbBr3 single crystals and CsPbBr3 crystalline phases dispersed in a KBr matrix

Spectra of steady-state X-ray excited luminescence (XEL) and thermally stimulated luminescence (TSL) of CsPbBr3 single crystals in the temperature range of 80–294 K were studied. Each of the measured XEL spectra of CsPbBr3 single crystal contain only one elementary band peaking at 535 nm, which can be attributed to the radiative decay of the matrix exciton. The activation energy of exponential luminescence thermal quenching in this range, as determined by Mott's formula, is equal to 75 meV, close to the hole trap depth of 110 meV obtained for the main TSL peak of this crystal at 125 K. This value of the XEL quenching activation energy is associated with the thermal deactivation of the exciton hole component in the CsPbBr3 matrix.Doping of KBr crystals with CsPbBr3 perovskite impurities (0.05–1 mol. %) leads to the formation of CsPbBr3 micro- and nanocrystals in a KBr matrix with characteristic spectra of exciton photo- and XEL luminescence. A five-fold increase in the intensity of XEL was registered in KBr: CsPbBr3 (0.05 mol. %) samples at 294 K compared to that of CsPbBr3 single crystal.The temperature dependence of the XEL intensity of KBr: CsPbBr3 crystals and the analysis of their TSL integral curves allow us to make a conclusion about the hole mechanism of high-energy excitation energy transfer from the matrix to the activator resulting in the appearance of typical exciton luminescence in CsPbBr3 nanoparticles.

Solvothermal synthesis of rhombic shape GdF<sub>3</sub>:Tb<sup>3+</sup> nanoparticles for biomedical applications

Purpose of the study. In this work, we have investigated the mechanism of structure formation of GdF3:Tb3+(15 %) nanocrystals synthesized by solvothermal synthesis in the temperature range from RT to 200 °C with a step of 50 °C.Materials and methods. Nanocrystals of GdF3:Tb3+(15 %) were synthesized by the solvothermal method using a high-pressure reactor (autoclave) designed for temperatures up to 250 °C. The structure, size and morphology were determined by transmission electron microscopy (TEM), the type of crystal lattice and the size of crystallites of nanoparticles were studied by X-ray diffraction (XRD), hydrodynamic size of nanoparticles, particle size distribution, ζ-potential, agglomeration of nanoparticles in colloidal solutions were determined by dynamic light scattering (DLS), the chemical composition of the nanocrystals surface was studied by Fourier-t ransform infra-red spectroscopy (FT-IR), the nanoparticles ability to absorb UV radiation was analyzed by UV-visible spectroscopy (UV-vis) and X-ray excited optical luminescence (XEOL).Results. With an increase in the temperature of the synthesis reaction, a structural change in the crystallites phase occurs from hexagonal to orthorhombic. At low temperatures, agglomerated particles consisting of hexagonal nanocrystals are formed, while at a temperature higher than the boiling point of the solvent, monodisperse rhombic- shaped nanoparticles with orthorhombic phase are formed. At mild temperatures, agglomerated particles with different morphology and with mixed hexagonal and orthorhombic phases are formed. Based on the analysis of X-ray spectrum, it was found that the size of GdF3:Tb3+(15 %) nanocrystals varies from 10 to 50 nm for different synthesis temperature conditions (T = RT, 50 °C, 100 °C, 150 °C, 200 °C). The hydrodynamic size of nanoparticles decreases with increasing synthesis temperature. All GdF3:Tb3+(15 %) nanocrystals obtained at different temperatures are transparent to visible light and absorb UV radiation. Absorption in the UV region increases with an increase in the size of particle crystallites. Upon X-ray irradiation of the colloidal GdF3:Tb3+(15 %) solution, X-ray excited optical luminescence spectra showed emission peaks at 490 nm, 543 nm, 585 nm and 620 nm.Conclusion. The mechanism of structure formation of rhombic‑ shaped GdF3:Tb3+(15 %) nanocrystals has been investigated. These monodisperse rhombic- shaped nanoparticles can be used for X-ray induced photodynamic therapy (X-PDT) of superficial, solid and deep-seated tumors.

Study on luminescent performance of Dy3+-, Tb3+-doped and Tb3+/Dy3+ co-doped TeO2-(Gd,Lu)2O3-WO3 glass scintillators

Three series of Dy3+-, Tb3+-doped and Tb3+/Dy3+ co-doped 40TeO2-20(Gd,Lu)2O3–40WO3 glasses with density of about 6.75 g/cm3 were successfully prepared by high temperature melt-quenching method. The luminescence properties of these rare earth ions doped 40TeO2-20(Gd,Lu)2O3–40WO3 glass were systematically studied by transmittance, photoluminescence (excitation and emission spectra), time-resolved emission spectra (TRES) and X-ray excited luminescence (XEL) spectra, together with the luminescence decay curves. The optimal doping concentration of Dy3+ and Tb3+ ions in 40TeO2-20(Gd,Lu)2O3–40WO3 glasses was determined under UV and X-ray excitation, respectively. It is found there is an efficient energy transfer from Dy3+ to Tb3+ ions in 40TeO2-20(Gd,Lu)2O3–40WO3 glass in photoluminescence spectra. However, it is not true under X-ray excitation due to the complicated physical process.

Effects of Preparation Atmosphere and Doping Concentration on Scintillation and Photoluminescence Properties of Lu2O3:Eu Scintillation Single Crystals

Lu2O3:1%Eu and Lu2O3:8%Eu series single crystals were grown by optical floating zone method under air, N2, and H2-Ar mixed atmosphere (5vol%H2 and 95vol%Ar). The effects of preparation atmosphere and doping concentration on the scintillation and photoluminescence properties have been investigated and discussed. Correlated measurements of afterglow curves, X-ray excited luminescence spectra, photoluminescence excitation and photoluminescence, photoluminescence decay, and thermal stimulated luminescence curves were performed. Although Eu(S6) luminescence can be significantly depressed under oxidizing atmosphere, Lu2O3:8%Eu grown under weak reducing atmosphere presents the lowest afterglow intensity. This phenomenon was explained by different interstitial oxygen atom concentrations in the samples.

Ce 3+:Lu 3Al 5O 12–Al 2O 3 optical nanoceramic scintillators elaborated via a low-temperature glass crystallization route

Transparent Ce:lutetium aluminum garnet (Ce:Lu₃Al₅O₁₂, Ce:LuAG) ceramics have been regarded as potential scintillator materials due to their relatively high density and atomic number (<i>Z</i>_eff). However, the current Ce:LuAG ceramics exhibit a light yield much lower than the expected theoretical value due to the inevitable presence of Lu_Al antisite defects at high sintering temperatures. This work demonstrates a low-temperature (1100 ℃) synthetic strategy for elaborating transparent LuAG–Al₂O₃ nanoceramics through the crystallization of 72 mol% Al₂O₃–28 mol% Lu₂O₃ (ALu28) bulk glass. The biphasic nanostructure composed of LuAG and Al₂O₃ nanocrystals makes up the whole ceramic materials. Most of Al₂O₃ is distributed among LuAG grains, and the rest is present inside the LuAG grains. Fully dense biphasic LuAG–Al₂O₃ nanoceramics are highly transparent from the visible region to mid-infrared (MIR) region, and particularly the transmittance reaches 82% at 780 nm. Moreover, Lu_Al antisite defect-related centers are completely undetectable in X-ray excited luminescence (XEL) spectra of Ce:LuAG–Al₂O₃ nanoceramics with 0.3–1.0 at% Ce. The light yield of 0.3 at% Ce:LuAG–Al₂O₃ nanoceramics is estimated to be 20,000 ph/MeV with short 1 μs shaping time, which is far superior to that of commercial Bi₄Ge₃O₁₂ (BGO) single crystals. These results show that a low-temperature glass crystallization route provides an alternative approach for eliminating the antisite defects in LuAG-based ceramics, and is promising to produce garnet-based ceramic materials with excellent properties, thereby meeting the demands of advanced scintillation applications.

Upconversion luminescence, scintillation properties and optical thermometry behaviors of Tm3+, Yb3+: Gd2Zr2O7 nanocrystals

The development of multifunctional nanocrystals has attracted growing interest lately in the biological and medical sciences. Herein, the dual-mode luminescence properties and optical thermometric performances of Tm3+, Yb3+: Gd2Zr2O7 nanocrystals synthesized by a facile hydrothermal method are investigated systematically. Upon 980 nm excitation, the upconversion (UC) luminescence spectra of the obtained samples consist of blue (485 nm), red (655 and 681 nm), and near-infrared (785 nm) emission bands of Tm3+ ions. Diversely, the X-ray excited luminescence (XEL) spectra contain a strong ultraviolet (UV) emission from Gd3+ ions (314 nm), a weak defect-related emission band (400–600 nm), and several tiny emissions from Tm3+ ions. To realize the optical thermometry in the biological window, the luminescence intensity ratio (LIR) between 3F2,3 → 3H6 (681 nm) and 1G4→3F4 (655 nm) transitions is employed for temperature sensing, giving high absolute and relative sensing sensitivities (Sa-max = ∼1064 × 10−4 K−1, Sr-max = ∼2.32%K−1). Therefore, the present Tm3+, Yb3+: Gd2Zr2O7 nanocrystals could be useful in optical thermometry, photodynamic therapy, and X-ray imaging.

Study on the luminescent properties of Eu3+-doped TeO2-GeO2-BaO scintillation glasses

Scintillation glasses for hadron calorimeter need high density and excellent luminescent properties. Eu3+-doped TeO2-GeO2-BaO scintillation glasses with the nominal composition of xTeO2-(60-x)GeO2-39BaO-1Eu2O3 (x = 20, 25, 30, 35, 40, 45, and 50) were prepared by melt-quenching method. The structural information induced by various TeO2/GeO2 ratios were discussed by means of density, FTIR spectra and transmittance spectra, together with the asymmetric ratios of Eu3+ ions and Judd-Ofelt analysis. The luminescent properties of Eu3+-doped TeO2-GeO2-BaO scintillation glasses are described byphotoluminescence (PL) and X-ray excited luminescence (XEL) spectra. The results suggest that both PL and XEL intensity of Eu3+-doped TeO2-GeO2-BaO scintillation glasses are observed to drops clearly with an increase in x values, whereas the glass density shows a slight increase. Therefore, a balance should be search for the possible scintillation application between the luminescent efficiency and the strict density requirement.

The self-absorption effect on the X-ray excited luminescence and cathodoluminescence spectra of YAG: Yb crystals

Y3Al5O12:Yb (YAG:Yb) crystal has been applied as not only the laser crystal with infrared (IR) luminescence but also the fast scintillation crystal with the fast ultraviolet (UV) scintillation light. In the investigation, both the X-ray excited luminescence (XEL) and cathodoluminescence (CL) spectra of YAG:Yb crystals with various Yb concentrations were measured and compared. Generally, the CL spectrum is considered to be equivalent to the XEL spectrum in characterizing the luminescence of scintillation crystals. However, the inconsistent correlations between Yb concentrations and the spectrally integrated XEL, CL intensities were observed for the UV luminescence. Meanwhile the consistent correlations between Yb concentrations and the spectrally integrated XEL, CL intensities were observed for the IR luminescence. The phenomenon was attributed to the stronger self-absorption effect in the XEL spectra measurements, compared to the CL spectra measurement. It indicates the correction on the luminescence intensity is needed in comparing the integrated XEL intensity of scintillation crystal with self-absorption effect.

Investigation on luminescence behavior of Mg4Ta2O9 through experimental and first-principles calculation methods

In this work, Mg4Ta2O9 single crystal was synthesized by optical floating zone method in N2 atmosphere. The luminescence behavior of Mg4Ta2O9 single crystal was investigated through experimental and first-principles calculation methods. Its photoluminescence, scintillation and thermal stimulated luminescence properties, including photoluminescence excitation, photoluminescence, photoluminescence decay, thermal stimulated luminescence and X-ray excited luminescence spectra, were measured. In addition, the temperature dependence of photoluminescence, photoluminescence decay and photoluminescence afterglow curves of Mg4Ta2O9 were measured and discussed. Combined with the experimental and density functional theory calculations result, the energy transfer schematic diagrams of the Mg4Ta2O9 were proposed to explain the photoluminescence, scintillation, and thermal stimulated luminescence behaviors.

Characterisation of Sm2+-doped CsYbBr3, CsYbI3 and YbCl2 for near-infrared scintillator application

Fast energy transfer from Yb2+ to Sm2+ is a requirement when using Yb2+ as a sensitiser for Sm2+ emission for near-infrared scintillator applications. This cannot be achieved through dipole-dipole interactions due to the spin-forbidden nature of the involved Yb2+ transition, making the rate of energy transfer too slow for application. This work explores whether exploiting the exchange interaction by increasing the Yb2+ concentration to 99% is an effective way to increase the rate at which energy is transferred from Yb2+ to Sm2+. The scintillation characteristics of CsYbBr3:1%Sm, CsYbI3:1%Sm and YbCl2:1%Sm single crystals were studied through 137Cs excited pulse height spectra, X-ray excited decay and X-ray excited luminescence spectra. An energy resolution of 7% and a light yield of 30,000 ph/MeV was achieved with CsYbI3:1%Sm. Photoluminescence spectroscopy and decay studies were performed to study the band structure and relaxation dynamics.

X-ray induced coloration behavior of Lu2O3:Eu transparent ceramics and the impact of ZrO2 and HfO2 sintering additives

Lu2O3:Eu, Lu2O3:Eu,Hf and Lu2O3:Eu,Zr transparent ceramics (TC) were fabricated using vacuum sintering followed by heat isostatic pressure (HIP). The structure of the samples was measured by X-ray diffraction (XRD). The X-ray induced coloration and bleaching behavior of Lu2O3:Eu TC is reported for the first time. The transmission and X-ray excited luminescence (XEL) spectra before and after irradiation and after bleaching were measured. By adopting the energy level diagram of Lu2O3:Eu calculated by first-principles calculation, coloration and bleaching mechanisms of Lu2O3:Eu TC were proposed. In addition, the impact of hafnia and zirconia on the optical, photoluminescence and scintillation properties of Lu2O3:Eu TC was discussed and analyzed through the morphology, photoluminescence and scintillation properties, including transmission curves, scanning electron microscope (SEM), photoluminescence excitation (PLE), photoluminescence (PL), PL decay curves, XEL curves and afterglow curves.

Optical and scintillation properties of aluminoborosilicate glass

The Circular Electron Positron Collider (CEPC) is a large international scientific facility proposed by the Chinese particle physics community. For the particle flow algorithms (PFA) oriented HCAL of the CEPC, an analog read-out option (AHCAL) is chosen in this regard. The proposal of silicon photomultiplier (SiPM) coupling with the glass scintillator as the detection unit HCAL is a new solution for the next generation calorimeter. The optical and scintilation characteristics of the aluminoborosilicate glass scintillator have been measured. When the wavelength is longer than 450 nm, the transmittance of the aluminoborosilicate glass is higher than 65%. In X-ray excited luminescence spectra, the integral intensity of the glass is 25.5% that of Bi4Ge3O12 (BGO) crystal. The energy resolution of the glass is approximately 27%. Moreover, the light yield of the glass is greater than 800 ph/MeV. The scintillating decay time of the fast and slow components is 262.10 ns (18%) and 1234.83 ns (82%), respectively. The difference between the scintillating and fluorescence decay time of the glass is explained by the luminescent mechanism. In addition, the afterglow of the glass was tested.

Crystal growth and luminescence characterizations of halide scintillators K2LaBr5:Eu2+

Recent researches have shown that Eu2+ ion heterovalently doped rare earth halide scintillators attract the attention of researchers. In this paper, the transparent K2LaBr5 scintillation crystals of centimeter size doped with heterovalent Eu2+ were successfully grow by the vertical Bridgman technique. X-ray powder diffraction analysis shows that the crystal has an orthonormal structure with space group Pnma(62). A small amount of Eu2+ doping does not change the internal structure of the crystal.The transmittance, the UV–visible excited spectrum and emission spectrum, X-ray excited luminescence spectrum, Photoluminescence decay time and scintillation pulse decay time have been measured at room temperature. The results show that the crystal has strong luminescence intensity, and the maximum emission peak is about 430 nm. The photoluminescence decay time of K2LaBr5:xmol.%Eu2+(x = 0.5, 1, 2) are 5.56 μs, 5.67 μs and 7.03 μs, respectively. The decay time of K2LaBr5:Eu2+ crystal under 137Cs 662 keV radiation is nanosecond, indicating that the K2LaBr5:Eu2+ crystal has fast decay characteristics and excellent time resolution performance.

Multi-functionalities of photoluminescence, X-ray excited luminescence and optical temperature sensing in Er3+ and Er3+/Yb3+ doped Gd2Zr2O7 phosphors

A series of Er3+-doped and Er3+-Yb3+ co-doped Gd2Zr2O7 phosphors were synthesized via hydrothermal method, and their multifunctional properties were studied in detail. The Raman spectra indicated that the products were the ordered pyrochlore phase of Gd2Zr2O7, which exhibited a good radiation resistance. The up-conversion (UC), down-conversion (DC) photoluminescence (PL) and X-ray excited luminescence (XEL) spectra of the Er3+: Gd2Zr2O7 samples showed the similar spectra profiles, which were composed of the prominent green (2H11/2/4S3/2→4I15/2) and weak red (4F9/2→4I15/2) emissions. The co-doping of Yb3+ ions was beneficial for the improvement in UC PL but led to the reductions in DC PL and XEL. Besides, the X-ray induced green emissions demonstrated a high-sensitivity to the dose rate and a long-term stability against the continuous X-ray irradiation. Moreover, using the fluorescence intensity ratio (FIR) technique, the temperature sensing behaviors were analyzed based on the thermally coupled levels (TCLs) 2H11/2 and 4S3/2 of Er3+. The FIRs were found to be insensitive to the excitation power variation, and the optimal relative sensing sensitivity reached ~1.1%K−1 at 298 K. These characteristics may enable the studied system applicable for optical thermometry, X-ray detection and X-ray imaging.

Visualizing the valence states of europium ions in Eu-doped BaAl2O4 using X-ray nanoprobe mapping.

This study develops and successfully demonstrates visualization methods for the characterization of europium (Eu)-doped BaAl2O4 phosphors using X-ray nanoprobe techniques. X-ray fluorescence (XRF) mapping not only gives information on the elemental distributions but also clearly reveals the valence state distributions of the Eu2+ and Eu3+ ions. The accuracy of the estimated valence state distributions was examined by performing X-ray absorption spectroscopy (XAS) across the Eu L3-edge (6.977 keV). The X-ray excited optical luminescence (XEOL) spectra exhibit different emission lines in the selected local areas. Their corresponding emission distributions can be obtained via XEOL mapping. The emission properties can be understood through correlation analysis. The results demonstrate that the main contribution to the luminescence intensity of the Eu-doped BaAl2O4 comes from the Eu2+ activator and the emission intensity will not be influenced by the concentration of Eu2+ or Eu3+ ions. It is anticipated that X-ray nanoprobes will open new avenues with significant characterization ability for unravelling the emission mechanisms of phosphor materials.

Optical properties of Dy2O3, Tb4O7 singly doped, Dy2O3/Tb4O7 codoped borogermanate-tellurite glasses for radiation application

In this paper, Dy2O3, Tb4O7 singly doped and Dy2O3/Tb4O7-codoped borogermanate-tellurite glasses for radiation application were synthesized by a melt-quenching method. The density of developed glasses exceeds 5.0 g/cm3, which is the fundamental requirement of dense scintillators in the application fields of medical imaging and high-energy physics engineering. The optical properties of these glass scintillators were systematically studied by transmittance, photoluminescence (PL) and X-ray excited luminescence (XEL) spectra, together with the corresponding photoluminescence dynamic process. The transmittance results reveal that the transmittance rate of all glasses can reach at the vicinity of 80%. The optimal content of Dy2O3 and Tb4O7 for both PL and XEL intensity were determined under ultraviolet light and X-ray excitation, respectively. The energy transfer occurred from Dy3+ to Tb3+ ions were demonstrated, and the energy transfer efficiency from Dy3+ to Tb3+ ions is observed to increase with higherTb4O7content. The scintillation efficiency of Dy3+, Tb3+doped, and Dy3+/Tb3+ co-doped borogermanate-tellurite scintillating glasses is about 10.45%, 41.38%, and 38.73% of the standard Bi4Ge3O12 (BGO) crystal, respectively.

Combining X-ray excited optical luminescence and X-ray absorption spectroscopy for correlative imaging on the nanoscale.

X-ray absorption and optical luminescence can both provide valuable but very different information on the chemical and physical properties of materials. Although it is known that the spectral characteristics of many materials are highly heterogeneous on the micro- and/or nanoscale, no methodology has so far been shown to be capable of spatially resolving both full X-ray absorption and X-ray excited optical luminescence (XEOL) spectra on the nanoscale in a correlative manner. For this purpose, the scanning transmission X-ray microscope at the HERMES beamline of the SOLEIL synchrotron was equipped with an optical detection system capable of recording high-resolution XEOL spectra using a 40 nm soft X-ray probe. The functionality of the system was demonstrated by analyzing ZnO powder dispersions - showing simultaneously the X-ray linear dichroism and XEOL behavior of individual submicrometric ZnO crystallites.