Bi12GeO20 Crystals Research Articles

Lattice dynamics of Bi12GeO20 crystal: Polarized Raman scattering and first-principles analysis

Our paper presents a combined experimental and theoretical study of the lattice dynamics of Bi12GeO20 crystal. Polarized Raman spectra were measured in two x-ray oriented single crystals. In a crystal of cubic symmetry, phonon modes of A- and E-types are spectroscopically indistinguishable. Using a special experimental technique, we separated the phonon modes that transform according to A and E irreducible representations. Since the number of E-type lines observed in Raman scattering is higher than theoretically allowed by group theory, we performed a first-principles calculation of the Bi12GeO20 lattice dynamics to accurately identify the symmetry of phonon modes. All experimental lines observed in Raman scattering are classified according to irreducible representations of the cubic I23 group. Using samples of different thicknesses, 10 mm and 0.120 mm, we have demonstrated that the optical activity plays an insignificant role at Raman backscattering in Bi12GeO20 crystal.

Modulation of components toward blue light emission and scintillation properties of Eu2+ activated Sr1-xLaxMgxAl12-xO19 crystal

The development of Eu2+-activated oxide materials with high efficiency, fast decay and narrow bandwidth emission in the visible region is still challenging for the field of luminescence and scintillation applications. Generally, Eu2+ in oxide hosts can emit intense and broad 5d-4f emission in the visible region, but efficient emitting with stable bivalence of Eu is rare in inorganic oxide system. In this work, a series of ASL:Eu2+ (Sr1-xLaxMgxAl12-xO19) powder samples with various La, Mg doping ratios were designed and synthesized to modulate the UV or X-ray excited luminescence properties, including redshift, quantum yield, and decaying lifetime. Moreover, an ASL:Eu2+ crystal with the optimal ratio x = 1/3 was grown, its scintillation performance was compared with standard Bi4Ge3O12 crystal sample and evaluated in detail. These results indicate that the ASL:Eu2+ crystal is potential scintillator as a kind of X-ray detection and provide a reference for the further development of high-performance Eu-activated oxide scintillation materials.

X-ray excited broadband blue emitting Lu2(1-x)Bi2xO3-PMMA thin films for high resolution imaging

In this paper, cubic-phase Lu2O3:Bi3+ nanoparticles, with a range of sizes between 110 and 180 nm, were obtained by a combination of co-precipitation and thermal annealing techniques. For these nanoparticles upon UV or X-ray excitation, strong broadband emission peaks at 410 and 480 nm corresponding to Bi3+ occupying S6 and C2 (Lu3+(S6) and Lu3+(C2)) sites, respectively, can be observed. On the basis of the concentration-dependent luminescence intensity ratios (I480(C2)/I410(S6)) of Bi3+(C2) to Bi3+(S6), the energy transfer from Bi3+(S6) to Bi3+(C2) can be confirmed at high Bi3+ concentration. In particular, their X-ray absorption coefficient, emission wavelength, afterglow level (60 ppm) and response time (465 ns) are almost comparable to those of the commercial Bi4Ge3O12 crystals. By the means of dispersing Lu1.98Bi0.02O3 nanoscintillators into organic polymer (PMMA)-acetone solution, the Lu1.98Bi0.02O3-PMMA flexible composite films exhibiting rapid response to X-ray photons, high X-ray sensitivity and radiation resistance, good mechanical performance and excellent environmental stability were prepared using a spin-coating technique. On the surface of X-ray imaging screen formed by the flexible dense composite films, the spatial resolution can reach to 6.0 lp/mm at a safe irradiation dose (4.6 μGy). Meanwhile, for the imaging screen using the flexible composite films after bended for thousands of times, we can observe clear image of each reed gap (300 μm) of the music box. For the Lu2O3:Bi3+-PMMA composite films, our results suggest that not only their scintillation properties are almost comparable to those of the commercial broadband Bi4Ge3O12 crystals, but also they might be applied in large-area and non-planar X-ray imaging.

Double Gain of Efficient UV‐C Phosphor and Fast Scintillator Based on Pr3+‐doped KY3F10 Nano‐Glass Composites

AbstractGlassy phosphors offer a promising opportunity to overcome the limits of polycrystalline counterparts, thanks to their merits including excellent optical transparency, abandonment of organic binders, and capability of drawing fibers, etc. However, research and development of glassy UV‐C phosphors and fast scintillators have seriously lagged behind crystals. Here, a new type of efficient UV‐C phosphors and fast scintillators (double gain) is developed from Pr3+‐doped transparent nano‐glass composites (nano‐GCs) containing KY3F10 nanocrystals. Such a material combines favorably the advantages of both crystal and glass, exhibiting intense interconfigurational 5d‐4f emissions of Pr3+ upon deep‐UV, high energy electron‐beam and X‐ray excitations. The emission profile ideally overlaps with the germicidal effectiveness curve. The Pr3+‐doped nano‐GCs are endowed with a radiative decay time shorter than that of extensively studied Ce3+‐doped glasses and nano‐GCs. They exhibit intense X‐ray excited radioluminescence that is comparable to the standard Bi4Ge3O12 (BGO) crystal and significantly stronger than Pr3+‐doped ZBLAN fluoride glass known for the high luminescence efficiency. An X‐ray imaging system with a good spatial resolution using the Pr3+‐doped nano‐GCs is also demonstrated.

Intense radioluminescence from transparent CsGd2F7: Ce3+ nano-glass scintillator

Nano-glasses are next-generation scintillators combining favorably the merits of both scintillator crystals and glasses. Here, a new nano-glass scintillator is prepared embedding CsGd2F7:Ce3+ nanocrystals (NCs). The microscopic morphology, particle size, and distribution of the NCs are studied by high resolution transmission electron microscopy. Significantly enhanced radioluminescence efficiency is obtained in the nano-glasses. The largest integrable intensity of X-ray excited luminescence is 316% of the standard Bi4Ge3O12 (BGO) crystal. A well-resolved full-energy peak with an energy resolution of 17.4% is registered for the 662 keV gamma rays, and the light yield is determined to be 827 ± 8 ph/MeV. The nano-glass scintillators exhibit good radiation hardness and thermal stability. As a proof of concept, an X-ray imaging system of a good resolution is built on the nano-glass scintillators.

X-ray imaging scintillator: Tb3+-doped oxyfluoride aluminosilicate glass

Scintillators are considered as a vital component for X-ray imaging due to their ability to convert X-ray into visible light. We synthesized Tb3+-doped oxyfluoride aluminosilicate glass scintillators by conditional melt-quenching method. These glass scintillators possess outstanding optical and scintillating properties. All glass scintillators have high transparency (exceed 83.3% at 475 nm), excellent internal quantum yield and suitable lifetime. The integrated luminescent intensity of optimal specimen excited by X-ray is about 224% compared to Bi4Ge3O12 crystal. The optimal glass scintillator has a good stability after continuous X-ray irradiation and exhibits profound spatial resolution in X-ray image (20 lp·mm−1). All outcomes demonstrate that Tb3+-doped oxyfluoride aluminosilicate glass scintillators have potential application for static X-ray imaging.

Design and elaboration of highly resolved and efficient Cu+-doped oxyfluoride glass scintillators for X-ray image based on response surface methodology

Bulk glass scintillators, which process the advantages of low cost, cheap elaboration, excellent transparency and high uniformly, have garnered great attention for X-ray imaging application. Cu+-doped oxyfluoride glass scintillators were designed and elaborated by using Al powder as reducing agent. The relationship of X-ray excited luminescence (XEL) of Cu+-doped glasses with doping concentration of Cu+ and the addition of Al content were investigated by the response surface methodology to get the optimal glass. The optimal glass scintillator shows high transmittance (90.0% at visible region), short lifetime (42.9 μs), high absorption efficiency (93.0% at 290 nm) and good internal quantum yield (75.2%). Excitedly, the integrated XEL intensity of optimal sample is 141% of that of Bi4Ge3O12 crystal. And its spatial resolution reaches 20 lp/mm for X-ray imaging. Above results illustrate the potential application of Cu+-doped oxyfluoride glass scintillators in X-ray imaging filed.

A novel scintillating material based on Cu+ doped borate glass

Luminescence glass is an inspiring scintillating material because of the unique merits including simple preparation process, mass production and low-cost. However, it is still a daunting challenge to explore the scintillating glass which can be applied in practical life. Herein, a novel Cu + doped borate glass scintillator was successfully fabricated under air atmosphere by introducing proper Si3N4 in melting process. The resultant glass exhibits broadband luminescence under ultraviolet (UV) light or X-ray excitation. Through the low temperature thermal treatment, both luminescence induced by UV and X-ray can be further enhanced. The quantum efficiency reaches as high as 74.2%. And the sample endows superior thermal stability with the emission intensity at 573 K still maintaining 62.5% of that at 303 K. The X-ray excited luminescence is 37.8% of that of the commercial Bi4Ge3O12 (BGO) crystal. Furthermore, the damaged sample even stimulated by high-energy X-ray can be restored to original level completely after heat treatment again. Besides, the sample presents outstanding optical thermometric performance based on the fluorescence decay lifetime. These findings confirm that the as-prepared Cu+ doped borate glass is a promising candidate applied in the areas of scintillator and temperature sensor.

Effect of B2O3 on luminescence and scintillation properties of Ce3+-doped gadolinium aluminium–silicate glass

Different B2O3 content was added to Ce3+–doped Gd2O3–Al2O3–SiO2 (xBGAS:1.1Ce3+, x = 0, 5, 10, 15) glasses to improve the photoluminescence (PL) and scintillation properties. The transmittance of 15BGAS:1.1Ce3+ glass is over 80%. The X–ray absorption near edge spectroscopy (XANES) spectra imply that Ce4+ can be effectively reduced to Ce3+ in the glasses by adding Si3N4. The excitation and emission spectra show a blue shift with increase of B2O3 content. The photoluminescence quantum yield (PL QY) increases with the increase of B2O3 content, reached the maximum of 59.55% when x = 15. The PL decay time of the glasses exhibits typical values (44–50 ns) due to 5d→4f transition of Ce3+ ions. The PL thermal activation energy become larger, indicating that xBGAS:1.1Ce3+ glasses have better luminescent thermal stability. The integral X–ray excited luminescence (XEL) intensity of the 15BGAS:1.1Ce3+ glass is 37.38% of Bi4Ge3O12 (BGO) crystal, and the light yield is 1267 ph/MeV with an energy resolution of 23.22% at 662 keV when exposed to γ–rays. With the increase of B2O3 content, the fast component of scintillation decay time gradually becomes shorter and the slow component becomes longer. The thermally stimulated luminescence (TSL) curves were measured to investigate the trap depth and density of defects in xBGAS:1.1Ce3+ glasses.

Preparation and scintillation properties of Ce3+/Tb3+-co-doped oxyfluoride glass for high-resolution X-ray imaging

Scintillator glasses have the potential for X-ray imaging owing to their low production cost, controllable shape and size, and uniform ion-doping concentration. In this study, Tb3+-doped and Ce3+/Tb3+-co-doped oxyfluoride scintillator (C4T9) glass samples were fabricated by high-temperature melting and quenching. In addition, the luminescence properties of the glass samples and the discrepancy in the energy transfer mechanism between Ce3+ and Tb3+ under ultraviolet (UV) light and X-ray excitation were investigated. The C4T9 glass sample showed excellent integral scintillation efficiency of 84.1% for commercial Bi4Ge3O12 (BGO) crystals. The spatial resolution of the C4T9 glass sample was higher than that of the commercial BGO crystal with 42.29 mGy s−1 X-ray irradiation, reaching 16 lp·mm−1. C4T9 glass is expected to become a key material in medical imaging, safety inspection, industrial inspection, and other fields.

Enhanced photoluminescence quantum yield of Ce3+‐doped aluminum–silicate glasses for scintillation application

AbstractCe3+‐doped 20Gd2O3–20Al2O3–60SiO2 (GAS:xCe3+) glasses (x = 0.3, 0.7, 1.1, 1.5, 1.9 mol%) with Si3N4 as a reducing agent were prepared. The density of the glasses is around 4.2 g/cm3. With the increase in the Ce3+ concentration, both the photoluminescence (PL) and PL excitation peaks of GAS:xCe3+ glasses show a redshift because the 4f–5d energy levels of Ce3+ ions are narrowed. PL quantum yield and PL decay time of GAS:xCe3+ glasses are 28.32–50.59% and 43–64 ns, respectively. In addition, they both first increases and then decreases with the Ce3+ concentration increasing, reached the maximum when x = 1.1 mol%. The integrated X‐ray excited luminescence (XEL) intensity of the GAS:1.1Ce3+ glass is 23.86% of that of Bi4Ge3O12 (BGO) crystal, and the light yield reaches 1200 ph/MeV with an energy resolution of 22.98% at 662 keV when exposed to γ‐rays. The PL and XEL thermal activation energies of GAS:xCe3+ glasses are independent of Ce3+ ions concentration. Scintillating decay time of the glasses exhibits two components consisting of nanosecond and microsecond levels, and the scintillating decay time gradually decreases with the Ce3+ concentration increasing. The difference between PL and scintillating decay time is discussed regarding the different luminescent mechanisms.

Photo and X-ray luminescence characteristics of CeF3 -doped SiO2 + B2O3 +AlF3 + NaF + CaF2 scintillating glasses

Fluoroborosilicate (SBFanc:SiO2 + B2O3 +AlF3 + NaF + CaF2) glasses with different CeF3 concentrations were fabricated by melt quenching technique to examine the scintillation properties of these glasses. The density and refractive index increase with an increase in CeF3 concentration. The structural properties of glasses were studied in the range of 800–4000 cm−1 using FT-IR transmittance spectroscopy. Luminescence characteristics of Ce3+:SBFanc glasses with an intensity peak around ∼345 nm (5d→4f) were studied using photo (λexc = 303 nm) and X-ray excited luminescence techniques. The energy transfer (ET) between Ce3+ -Ce3+ ion pairs taking place via dipole-dipole type interaction for the concentration quenching of Ce3+ emission on the basis of Dexter and Schulman theory. The PL decay curves can be fitted by a double exponential function with the decay times 64.28–99.87 ns and 15.78–21.29 ns for slow and fast decay components, respectively. The highest integrated light emission intensity of Ce3+:SBFanc glasses stimulated by X-ray is 35% of commercial Bi4Ge3O12 crystal and can be used for the scintillator materials.

Characterisation of surface charge density and net electric field during parallel-plate dielectric barrier discharge generated in atmospheric-pressure air

We measured the surface charge density in a parallel-plate dielectric barrier discharge (DBD) using the Pockels effect, and the axial and lateral components of the net electric field were evaluated for different gap lengths and applied voltages. The DBD was driven by a 5 kHz sinusoidal voltage in gap lengths of 0.5, 0.3, and 0.1 mm at atmospheric pressure with Bi4Ge3O12 crystal as a dielectric. Typical microdischarges (MDs) were observed for every gap length, and the number of MDs increased with the increasing applied voltage. As the gap length decreased, the spot radius of a single MD decreased, whereas the peaks of charge density were almost the same, indicating that the amount of charge transported per unit MD is limited for short gaps. The spatial memory effect, in which MDs occur at the same position in successive cycles, was not always observed under the experimental conditions, and it was evaluated considering the surface charge density distributions. Whether the memory effect works is determined by the surface charge density, and it is likely to occur under a balance between positive and negative charges across successive half-cycles. The net electric field was estimated from surface charge measurements. The axial component of the net electric field strength increased up to 150–170 Td before the MD occurred, and it decreased below 100 Td by the surface charge deposited by MD, being approximately 50%–60% of the external field amplitude. The maximum value of the lateral component of the electric field was approximately 150 Td at the edge of the MD spot with a gap length of 0.5 mm, and it decreased as the gap length decreased. As a negative surface charge generated a weaker lateral field than a positive one, the electric field distribution differed between anodic and cathodic dielectrics.

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.

Photochromic tuning and scintillation properties of Tb3+/Eu3+ co-doped calcium gadolinium zinc borosilicate glass

Tb3+/Eu3+ co-doped Al2O3-B2O3-SiO2-CaO-Gd2O3-ZnO (ABS-CGZ) borosilicate glass with high transmittance (∼ 80%) and density (4.2∼4.3 g/cm3) were produced by melt-quenching method, and their luminescence and scintillation characteristics were investigated. X-ray diffraction (XRD) of prepared glass exhibited long-range disordered interior structures. As the concentration of Eu3+ ions increased, there were variations in the characteristic emission peak intensities and the decay times of Tb3+ and Eu3+ ions, suggesting energy transfer from Tb3+ to Eu3+ ions. Furthermore, the integrated scintillation efficiency of the glass (Eu3+, 0.8mol%) reached 40% of the commercial Bi4Ge3O12 (BGO) crystal, indicating that co-doped glass possessed excellent scintillation properties. Moreover, the glass exhibited typical green and red emissions at excitation wavelength of 378 and 395 nm, and the color tuning of green to red light emission was observed with variation in Eu3+ ions doping concentration. The application range of borosilicate glass is further expanded based on the findings of this study.

Efficiency Properties of Cerium-Doped Lanthanum Chloride (LaCl3:Ce) Single Crystal Scintillator under Radiographic X-ray Excitation

The aim of this study is to evaluate the suitability of crystalline scintillator LaCl3:Ce for possible use in hybrid medical imaging systems, such as PET/CT and SPECT/CT scanners. For this purpose, a single crystal (10 × 10 × 10 mm3) was irradiated by X-rays within the tube voltage range from 50 to 150 kVp, and the absolute efficiency (AE) was measured experimentally. The energy absorption efficiency (EAE), quantum detection efficiency (QDE), and the spectral compatibility with various optical detectors were also calculated with the use of mathematical formulas. The results were compared with published data for Bi4Ge3O12 (BGO), Lu2SiO5:Ce (LSO), and CdWO4 single crystals of equal dimensions, commonly used in medical imaging applications. The luminescence efficiency values of the examined crystal were found to be higher than those of LSO, BGO, and CdWO4 crystals, within the whole X-ray tube voltage range. In the matter of EAE, LaCl3:Ce demonstrated reduced performance with respect to LSO and CdWO4 crystals. The emission spectrum of LaCl3:Ce was found to be compatible with various types of photocathodes and silicon photomultipliers (SiPMs). Considering these properties, LaCl3:Ce crystal could be considered suitable for use in hybrid medical imaging systems.

Luminescence and Energy Transfer of Tb3+/Dy3+ Co-Doped SiO2-Al2O3-B2O3-La2O3-Gd2O3 Glasses

Tb3+/Dy3+ co-doped glass with host system of SiO2-Al2O3-B2O3-La2O3-Gd2O3 were prepared by melt-quenching method. The photoluminescence occurred under the transitions, 5D3, 5D4 → 7FJ of Tb3+ and 4F9/2 → 6HJ of Dy3+ doped in glass. The emission spectra showed various transitions from the excited Tb3+, Dy3+ and Gd3+ ions which were calculated the color of emitted light and displayed in CIE diagram. The mixing emission of Tb3+ and Dy3+ (λex = 376 nm and 349 nm) performed the yellowish-green color, while the energy transfer from Gd3+ (λex = 270 nm) made Tb3+ and Dy3+ generating the white light. The energy transfer processes between Tb3+, Dy3+ and Gd3+ ions were verified by the excitation and emission spectra. The photoluminescence decay times of Tb3+ and Dy3+ in this glass are in millisecond order. The light yield of glass under excitation with 5.50 MeV of α particles were investigated and compared to Bi4Ge3O12 (BGO) crystal. This work could be useful for light source medium and radiation detection material.

Pr3+ deactivation effect to Tm3+ at ∼1.5 μm emission in Bi4Ge3O12 crystals grown by the micro-pulling-down method

Tm3+, Pr3+ co-doped Bi4Ge3O12 (Tm,Pr:BGO) crystals with various Pr3+ doping concentration were successfully grown using the micro-pulling-down (μ-PD) method. The use of Pr3+ co-doping for deactivating the Tm3+ ions at 1.5 μm emission was investigated in the BGO single crystal for the first time. The effect of Pr3+ concentration on the spectroscopic properties of Tm,Pr:BGO crystals were demonstrated. In addition, the fluorescence lifetime of Tm3+:3F4 level of 0.5 at.% Pr, 2 at.% Tm:BGO crystal was quenched effectively (from 5.64 ms down to 0.36 ms) and the population inversions between Tm3+:3H4 and 3F4 levels are enhanced to achieve a four-level laser system at 1.5 μm.

Scintillation properties of Ce3+/Tb3+ co-doped oxyfluoride aluminosilicate glass for exploration of X-ray imaging

Ce3+ or Tb3+ single-doped and Ce3+/Tb3+ co-doped oxyfluoride scintillation glass samples were prepared by high temperature melting method. The structures were analyzed by X-ray diffraction (XRD), the optical and luminescent properties were studied by transmittance, photoluminescence excitation, photoluminescence, X-ray excited luminescence (XEL) and fluorescence decay. The luminescence intensity in the Ce3+/5 mol% Tb3+ co-doped (CT5) glass sample under 304 nm light and X‐ray excitation is significantly enhanced compared to 5 mol% Tb3+ single-doped (T5) glass sample. The maximum integrated XEL intensity of CT5 glass sample is about 67% of the standard Bi4Ge3O12 (BGO) crystal. Through the study of energy transfer mechanism, the results indicate that there is an energy transfer from Gd3+ ions or Ce3+ ions to Tb3+ ions. The lifetime of CT5 glass sample is 2.13 ms. The obtained results confirm that CT5 glass sample could be a promising scintillating material used in X-ray imaging. So we have demonstrated X-ray imaging using Ce3+/1–15 mol% Tb3+ co-doped (CT1-15) glass samples and confirmed they can reach a spatial resolution of 10.0 lp/mm. Further, the X-ray imaging effect of CT5 glass sample is the best, and the capability of CT5 glass sample for X-ray imaging application is confirmed.

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.