Scintillation properties of Ce3+-doped YCl3 and YBr3

The dependence of the scintillation properties of Ce³⁺-doped YCl₃ and YBr₃ on activator concentration (0.5, 1 and 2 mol%) has been studied. The radioluminescence spectra of both materials contain asymmetric bands with maxima located at 3.13 eV (383 nm) for YCl₃:Ce³⁺ and 2.84 eV (422 nm) for YBr₃:Ce³⁺. The scintillation pulse decay curves for both materials are described by two components with decay constants of 37 and 640 ns for YCl₃:Ce³⁺ and 36 and 450 ns for YBr₃:Ce³⁺, the fractions of the faster component being 86 and 79 per cent, respectively. The dependences of the light yield of the studied materials on Ce³⁺ concentration pass through a maximum near 1 mol% of the activator, and the maximum light yields (relative to NaI:Tl) are 8700 photons per MeV for YCl₃:Ce³⁺ and 20,600 photons per MeV for YBr₃:Ce³⁺.     

The luminescence and energy transfer in Pr3+–Ce3+ co-doped Lu0.8Sc0.2BO3 crystals

Lu_0.8Sc_0.2BO₃ crystals doped with 1 at%Ce³⁺ and co-doped 0.1 at% and 0.5 at%Pr³⁺ were grown by the Czochralski method. The concentrations of Pr³⁺ and Ce³⁺ in crystals were measured by the ICP-AES method. Absorption spectra, VUV–UV spectra, fluorescence decay time and X-ray excitation luminescence spectra were investigated at room temperature. The excitation luminescence spectra of Ce³⁺ emission and decay curves from the lower excited state levels of the 4f¹5d¹ and 5d¹ electronic configurations of the Pr³⁺ and Ce³⁺ conspicuously indicated the non-radiative energy transfer from Pr³⁺ to Ce³⁺. The detailed pathways were shown in the energy level diagram of the respective Ce³⁺ and Pr³⁺ in Lu_0.8Sc_0.2BO₃ host. In addition, the scintillation efficiency data indicated that the energy transfer effect is directly associated with the Pr³⁺ concentration.     

Crystal growth,luminescence and scintillation properties of Eu2+:CeBr3 crystals

Eu²⁺:CeBr₃ crystals were grown by vertical Bridgman growth method and slight aliovalent doping of Eu²⁺ in the CeBr₃ crystal did not change the crystal structure. The X-ray stimulated luminescence, photoluminescence, decay kinetics and scintillation properties were investigated at room temperature. The X-ray stimulated luminescence spectra exhibited wide broad emission bands from 3.54 eV to 2.95 eV in the Eu²⁺:CeBr₃ crystal with high content of 620 ppm of Eu²⁺, which were the overlap of the emission bands ascribed to 5d → 4f transition of Ce³⁺ and 4f⁶5 d¹ → 4f⁷ transition of Eu²⁺, respectively. When the content of Eu²⁺ was decreased to 70 ppm, another emission band centered at 2.29 eV was observed. The photoluminescence spectra showed the energy transfer from Ce³⁺ to Eu²⁺. This decreased the Ce³⁺ emission intensity but enhanced the Eu²⁺ emission intensity. The photoluminescence decay time of Ce³⁺ emission decreased from 14 ns to 10 ns when the content of Eu²⁺ increased from 70 ppm to 620 ppm. The decay time of the emission of 525 nm did not change with the excitation wavelength and Eu²⁺ content, which could be assigned to the excitons that were bound on Eu²⁺ related centers. The light output of the Eu:CeBr₃ crystal under the excitation of ²⁴¹Am radioactive source was less than 20.2% of Tl:NaI crystal.     

铈离子掺杂浓度对氯化镧(LaCl_3:Ce)闪烁晶体发光性能的影响

本文采用垂直Bridgman法,分别生长了未掺杂LaCl3和掺有不同浓度CeCl3的LaCl3闪烁晶体,并对它们的透光性质、发光性质和光衰减特性进行了测试和对比分析.发现未掺杂LaCl3晶体的吸收边位于215 nm附近,本征发射峰为405 nm,衰减时间在1μs以上.该发光属于纯氯化镧晶体的自陷激子发射,但随着CeCl3掺杂浓度的提高,源于自陷激子(STE)的本征发射强度逐渐降低,LaCl3:Ce晶体中的吸收边逐渐红移至300nm,由Ce3+中心所产生的5d→4f发射逐渐增强,其衰减时间加快至～20 ns.这种现象被解释为LaCl3晶格中的自陷激子向Ce3+离子发光中心的能量传递作用所致.     

Luminescence properties of Ce3+ doped gadolinium-calcium-silicaborate glass scintillator

In this work, the Ce³⁺ doped gadolinium-calcium-silicaborate glass scintillators of the composition ratio 25Gd₂O₃:10CaO:10SiO₂:(55−x)B₂O₃:xCeF₃, have been fabricated by using the melt-quenching technique. The doping concentration of the Ce³⁺ was varied from 0.05 mol% to 2.5 mol%. The 4f-5d transition of the Ce³⁺ allowed scintillation with a fast decay time. The absorption spectrum, X-ray induced emission spectrum, photo luminescence spectrum, laser luminescence spectrum and decay time of the scintillators were measured for studying the luminescence properties. From the X-ray induced emission spectrum result, we checked the trend between doping concentration and light yield. The laser induced luminescence spectrum was measured while changing the temperature from 300 K to 10 K. We also measured the decay time by using the laser excitation of the 0.15 mol% Ce³⁺ doped glass scintillator.     

Luminescence spectroscopy of Ce3+-doped ABaPO4 (A=Li, Na, K) phosphors

Ce³⁺ doped ABaPO₄ (A=Li, Na, K) phosphors were prepared by conventional high temperature solid-state reaction. The phosphors were investigated by XRD, photoluminescence excitation and emission spectra, and luminescence decay curves. The five 5d levels corresponding to the 4f¹→4f⁰5d¹ transition of Ce³⁺ ions were identified. The spectroscopic parameters, e.g., the 5d barycenter, the crystal-field splitting, and the Stokes shift, were discussed. LiBaPO₄:Ce³⁺ phosphor could be efficiently excited by the near-UV lights (330–420 nm) and showed a broad emission band in the range of 430–620 nm with the maximum wavelength at 468 nm. In contrast, Ce³⁺-doped NaBaPO₄ and KBaPO₄ showed only excitation bands in a limited UV region (230–370 nm) and have blue emission at 385 nm and 416 nm, respectively. The temperature quenching of luminescence and the chromaticity coordinates were reported. The luminescence properties were discussed by analyzing the crystal structure and the local surroundings of Ce³⁺ ions on the Ba²⁺ sites.     

Luminescence and Scintillation Characterization of Cs2NaGdBr6: Ce3+ Single Crystal

Luminescence and scintillation properties of newly discovered bromo-elpasolites Cs₂NaGdBr₆: Ce³⁺ (CNGB: Ce³⁺) are presented. Single crystals of CNGB: Ce³⁺ with dimensions up to Ø7×10 mm³ are successfully grown by the Bridgman technique. X-ray excited luminescence measurements of the grown samples showed a broad emission band in the wavelength range from 365 to 470 nm. It offered an energy resolution of 5.1% (FWHM) at 662 keV for 10% Ce sample. The light output of the investigated samples increases along with cerium concentration. A maximum light yield of ～36,800 ph/MeV is measured for the 10% Ce sample crystal. Under γ-ray excitation, CNGB: Ce³⁺ crystals showed three exponential decay time components. The scintillation mechanism in the sample crystal is presented.     

Influence of lead-related centers on luminescence of Ce3+ and Pr3+ centers in single crystalline films of aluminium perovskites and garnets

Luminescence characteristics of Ce³⁺- and Pr³⁺-doped aluminium perovskite (LuAlO₃, YAlO₃) and garnet (Lu₃Al₅O₁₂, Y₃Al₅O₁₂) single crystalline films, prepared by the liquid phase epitaxy method with the use of the PbO-based flux, were investigated by the time-resolved spectroscopy methods in the 80–300 K temperature range. The influence of various lead-related centers on the characteristics of the Ce³⁺- and Pr³⁺-related luminescence centers was studied. It was found that the presence of lead-related centers in the single crystalline films results in a decrease of the quantum efficiency and appearance of undesirable slow components in the luminescence decay kinetics. The possibilities of improving the scintillation characteristics of the single crystalline films were considered.     

Scintillation properties of Cs2LiGdCl6: Ce3+

In this communication, we investigated the scintillation properties of Cs₂LiGdCl₆:10% Ce³⁺ single crystal. This scintillation crystal is grown by using the vertical Bridgman technique. X-rays induced emission spectra show that, Cs₂LiGdCl₆:10% Ce³⁺ emits into the Ce³⁺ band, spanning from 365 nm to 450 nm wavelengths. Under γ-ray excitation, the sample crystal shows three main decay time components of 129 ns (51%), 573 ns (32%) and 8.9 μs (17%). It offers an energy resolution of 5.0% (FWHM) for the 662 keV full absorption peak at room temperature. We measured an absolute light yield of 20,000 photons/MeV of absorbed γ-ray energy. We found that with a little exposure to the air, the scintillation properties of the Cs₂LiGdCl₆:10% Ce³⁺ crystal deteriorate, which is attributed to the highly hygroscopic nature of this material. We believe that the Cs₂LiGdCl₆:10% Ce³⁺ crystal can be a promising material for medical imaging and radiation detection. Moreover due to the presence of Li and Gd constituents, this scintillation crystal can also be the possible candidate for thermal neutron detection.     

Green light emission by Ce3+ and Tb3+ co-doped Sr3MgSi2O8 phosphors for potential application in ultraviolet whitelight-emitting diodes

Sr₃MgSi₂O₈:Ce³⁺, Tb³⁺ phosphor samples were prepared using a solid-state reaction technique, and the photoluminescence properties and energy transfer were investigated. Effective energy transfer occurred in Ce³⁺/Tb³⁺ co-doped Sr₃MgSi₂O₈ phosphors. Co-doping of Ce³⁺ was found to enhance the emission intensity of Tb³⁺ to a certain extent by transferring energy to Tb³⁺. The Ce³⁺/Tb³⁺ energy transfer was thoroughly investigated through its emission/excitation spectra and photoluminescence decay behavior. The color emitted by Sr₃MgSi₂O₈:Ce³⁺, Tb³⁺ phosphors varied from blue to green and can be controlled by altering the concentration ratio of Ce³⁺ to Tb³⁺. These results indicate that Sr₃MgSi₂O₈:Ce³⁺, Tb³⁺ may be useful as a green-emitting phosphor for ultraviolet whitelight-emitting diodes.     

Scintillation properties of pure and Ce3+-doped SrF2 crystals

In this paper results of scintillation properties measurements of pure and Ce³⁺-doped strontium fluoride crystals are presented. We measure light output, scintillation decay time profile and temperature stability of light output. X-ray excited luminescence outputs corrected for spectral response of monochromator and photomultiplier for pure SrF₂ and SrF₂-0.3 mol% Ce³⁺ are approximately 95% and 115% of NaI–Tl emission output, respectively. A photopeak with a 10% full width at half maximum is observed at approximately 84% the light output of a NaI–Tl crystal after correction for spectral response of photomultiplier, when sample 10 × 10 mm of pure SrF₂ crystal is excited with 662 keV photons. Corrected light output of SrF₂-0.3 mol% Ce³⁺ under 662 keV photon excitation is found at approximately 64% the light output of the NaI–Tl crystal.     

Study of the correlation of scintillation decay and emission wavelength

In photoluminescence which directly excites the emission center of phosphor material is known to have a correlation between the emission wavelength and the decay time based on quantum mechanics. In scintillation phenomenon, host lattice of the material is first excited by ionizing radiation and then the excitation energy is transferred to emission centers. For the first time, we investigated the correlation between the scintillation decay and the emission wavelength by using pulse X-ray equipped streak camera system which could observe time and wavelength resolved scintillation phenomenon. Investigated materials were Ce³⁺, Pr³⁺ and Nd³⁺ doped oxides and fluorides which all showed 5d-4f transition based emission. As a result, we obtained the relation that τ (scintillation decay time) was proportional to the λ^2.15 (emission wavelength).     

Decay of the Ce3+ luminescence of LaMgAl11O19 : Ce3+ and of CeMgAl11O19 activated with Tb3+ or Eu3+

Decay measurements have been performed on the Ce³⁺ luminescence of LaMgAl₁₁O₁₉ : Ce³⁺ and of CeMgAl₁₁O₁₉ activated with Tb³⁺. For all samples, the decay was found to be nearly exponential over at least two decades, and the decay time constant was practically the same, being ≈20 ns. From these results and from quantum efficiency data of the Ce³⁺ luminescence, conclusions are drawn about the various energy transfers and quenching interactions occurring in these compounds.     

Luminescent and scintillation properties of YAG:Dy and YAG:Dy,Ce single crystalline films

The paper is devoted to investigation of the luminescent properties of Dy³⁺ and Dy³⁺-Ce³⁺ doped single crystalline films (SCF) grown by LPE method from PbO–B₂O₃ flux. We have found that the YAG:Dy and YAG:Dy,Ce SCFs possess bright cathodoluminescence in the visible range and good scintillation figure of merit. For this reason LPE grown YAG:Dy and YAG:Dy,Ce SCF are proposed for different applications, namely, as cathodoluminescence screens or screens for microimaging. The Dy³⁺ co-doping can be also proposed for improvement of the scintillation efficiency of the Ce³⁺ doped garnet compounds in the SCF form due to Dy³⁺→ Ce³⁺ energy transfer and removing the trap related centers in the above RT range.     

Luminescent properties of SrAl2B2O7: Ce, Tb

By using metal nitrates as starting materials, SrAl₂B₂O₇: Tb³⁺ and SrAl₂B₂O₇: Ce³⁺, Tb³⁺ powder phosphors were prepared by sol-gel method. X-ray diffraction (XRD), photoluminescence excitation and emission, as well as kinetic decays were employed to characterize the resulting samples. The results show that energy transfers from Ce³⁺ to Tb³⁺ ions. The emission intensity of Tb³⁺ ions in SrAl₂B₂O₇ could be greatly intensified when Ce³⁺ ions are doped into SrAl₂B₂O₇: Tb³⁺. The decay times of SrAl₂B₂O₇: Tb³⁺ were prolonged when Ce³⁺ ions were doped. The doping of Ce³⁺ ions not only improved the luminescent intensity, but also made the materials gets stable luminescent properties.     

VUV spectroscopic properties of Ce and Pr-doped AREP2O7-type alkali rare earth diphosphates (A=Na, K, Rb, Cs; RE=Y, Lu)

Spectroscopic properties of Ce³⁺ and Pr³⁺-doped AREP₂O₇-type alkali rare earth diphosphates (A=Na, K, Rb, Cs; RE=Y, Lu) have been investigated using VUV spectroscopy technique. Ce³⁺-doped samples show typical Ce³⁺ emission in the range of 325-450 nm. The strong host absorption band starting at around 160 nm indicates that the optical band gap of AREP₂O₇ hosts is at least 7.7 eV, and the host→Ce³⁺ energy transfer process is rather efficient. However, AREP₂O₇:Pr³⁺ samples show less efficient host→Pr³⁺ energy transfer. The direct Pr³⁺ 4f²→4f¹5d¹ excitation, which are 12160±640 cm⁻¹ higher respect to that of Ce³⁺, leads to strong 4f¹5d¹→4f² emission bands in the range of 230-325 nm but no obvious 4f²→4f² emission lines.     

Growth and luminescence properties of single-crystalline films of <Emphasis Type="Italic">R</Emphasis>AlO<Subscript>3</Subscript> (<Emphasis Type="Italic">R</Emphasis> = Lu,Lu-Y,Y, Tb) perovskite

The conditions and the mechanisms of crystallization by liquid-phase epitaxy of undoped and Ce³⁺-doped RAlO₃ (R = Lu, Lu-Y, Y, Tb) single-crystalline films on YAlO₃ single-crystalline substrates at a considerable mismatch between the lattice constants of the single-crystalline films and the substrate are analyzed. The maximum values of this mismatch at which the stable growth of the single-crystalline films is observed are determined. It is demonstrated that transition layers are present between the substrates and the grown single-crystalline films in which the difference between the lattice parameters of the single-crystalline film and the substrate is diminished. The optical and luminescence characteristics of the undoped and Ce³⁺-doped RAlO₃ (R = Y, Y-Lu, Lu, Tb) single-crystalline films, as well as the scintillation characteristics of the (Lu-Y)AlO₃: Ce single-crystalline films under excitation by alpha-particles of the ²³⁹Pu source (5.15 MeV), are investigated.     

Luminescence and scintillation properties of Y<Subscript>3</Subscript>A<Subscript>l5</Subscript>O<Subscript>12</Subscript>:Ce single crystals and single-crystal films

Luminescence and scintillation properties of Y₃A_l5O₁₂:Ce single crystals grown from the melt by the Czochralski and horizontal directed crystallization methods in various gas media and Y₃A_l5O₁₂:Ce single-crystal films grown by liquid-phase epitaxy from a melt solution based on a PbO-B₂O₃ flux have been comparatively analyzed. The strong dependence of scintillation properties of Y₃A_l5O₁₂:Ce single crystals on their growth conditions and concentrations of Y_Al antisite defects and vacancy defects has been established. Vacancy defects are involved in Ce³⁺ ion emission excitation as the centers of intrinsic UV luminescence and trapping centers. It has been shown that Y₃A_l5O₁₂:Ce single-crystal films are characterized by faster scintillation decay kinetics than single crystals and a lower content of slow components in Ce³⁺ ion luminescence decay during high-energy excitation due to the absence of Y_Al antisite defects in them and low concentration of vacancy defects. At the same time, the light yield of Y₃A_l5O₁₂:Ce single-crystal films is comparable to that of single crystals grown by directed crystallization due to the quenching effect of the Pb²⁺ ion impurity as a flux component and is slightly lower (∼25%) than the light yield of single crystals grown by the Czochralski method.     

Investigation of gain characteristics in mixed crystals LiMeF4 (Me = Y,Lu, Yb) doped by Ce3+ ions

Differential gain spectra in the range 295–335 nm were measured in crystals of scheelite structure LiY_{1 ? x} Lu _x F₄ (x = 0–1), doped by Ce³⁺ ions. It is shown that variation of Lu³⁺ and Y³⁺ ions relative content in LiY_{1 ? x} Lu _x F₄ crystals allows to manipulate the spectral width of the amplification band. Cross-sections of excited-state absorption at the wavelengths of Ce³⁺ luminescence, probability ratios of formation and thermal destruction of color centers depending on the Y³⁺ ions content in LiY_{1 ? x} Lu _x F₄ crystals were estimated. Even better gain characteristics have been demonstrated by LiLuF₄:Ce³⁺, doped by Yb³⁺ ions. The highest optical gain coefficient with a wide amplification band among studied samples was observed in LiLuF₄:Ce³⁺ crystal, codoped by Yb³⁺ ions.     

Synthesis and scintillation properties of GdCl3:Ce3+ (Gd1−xCexCl3, x = 0.005–0.08)

Single crystals of GdCl₃ doped with different concentrations of Ce³⁺ have been grown using the Bridgman–Stockbarger technique and their luminescence and scintillation properties were investigated. The luminescence spectrum of GdCl₃:Ce³⁺ is complex and consists of two bands with maxima at 350 nm and 370 nm. The maximal light yield in GdCl₃:Ce³⁺ was observed at ～1 mol% of Ce³⁺ (more than 38 000 ph/MeV).