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With the rapid development of silicon-based light detectors with high detection efficiency and long-wavelength sensitivity, the development of near-infrared scintillation crystals has become a hotspot. Especially, the Sm2+ doped europium-based halide crystals exhibit excellent near-infrared luminescence properties. In this paper, Cs4 EuI6: Sm near-infrared scintillation crystals with a size of cm-level were successfully prepared by Bridgman method. The composition and structure were discussed by XRD, XPS and ICP-OES methods, indicating that the Sm2+ was introduced and has no obvious effect on the crystal structure of the matrix. Under ultraviolet and X-ray excitation, the crystal has two luminescence centers (Eu2+ and Sm2+), and the emission peaks are located at 450 and 840 nm, respectively, corresponding to the 5d→4f luminescence of Eu2+ and Sm2+. The decay time of Eu2+ and Sm2+ is at the level of microsecond under ultraviolet excitation. The results show that the emission wavelength gradually varies from blue to near infrared as Sm2+ doping concentration increased. The effects of Sm2+ concentration on the luminescence properties, Eu2+ -Sm2+ energy transfer and decay time of the crystals were also studied, which means that the luminescence properties can be tuned by adjusting the Sm2+ doping concentration. [ABSTRACT FROM AUTHOR]

In this study, we fabricated Cs 3 ScCl 6 crystals doped with different concentrations of Ce and investigated their luminescence properties. In both the photoluminescence (PL) and scintillation spectra, emission bands attributable to Ce3+ 5d–4f transition were observed. The PL temporal profiles revealed decay time constants of ~35 ns, which are typical values for Ce3+ 5d–4f transition. In the scintillation temporal profiles, two decay components were observed. The fast and slow components could be attributed to Ce3+ 5d–4f luminescence and self-trapped excitons (STEs) or a slow energy transfer from STEs to Ce3+, respectively. The maximum light yield was 9200 photons/MeV for a Ce concentration of 0.5 mol%. [ABSTRACT FROM AUTHOR]

The study of optical and photoluminescence properties of codoped Lu 2 SiO 5 :Ce, Yb single crystals was performed using conventional spectroscopy as well as time-resolved spectroscopy under excitation by pulsed synchrotron radiation. It was shown that the quenching of cerium luminescence is due to the nonradiative energy transfer from Ce3+ to Yb3+ ions. It was confirmed also that such energy transfer is not cooperative process. According to the constructed vacuum referred binding energy diagram the possible mechanism of quenching of cerium luminescence is the metal-to-metal electron transfer from Ce3+ to Yb3+. • The formation of luminescence properties of LSO:Ce,Yb crystals were studied at UV-VUV excitation. • The nonradiative energy transfer from the cerium to ytterbium has been shown. • The energy transfer mechanism is not cooperative. • Vacuum referred binding energy diagram for Lu 2 SiO 5 :Ce,Yb was constructed. [ABSTRACT FROM AUTHOR]

A novel NIR emitting scintillator with 825 nm was developed by doping Sm2+ in Cs 4 Eu(Br,I) 6 crystal. The single crystals of Cs 4 Eu(Br,I) 6 :Sm were successfully grown by the Bridgman method. The crystal structure and valence state was approved by XRD and XPS methods. The luminescence properties and energy transfer were systematically investigated. The energy transfer mechanism is variable for different Sm2+ concentration. The PL decay profiles show that the Sm2+-related emission has fast decay of nanosecond. The proportion of fast decay can be tunable by adjusting Sm2+ doped concentration. The Sm2+ doped europium -host material will have a potential application for unclear detection as near-infrared (NIR) scintillators. • The novel NIR emitting Cs 4 Eu(Br,I) 6 :Sm scintillation crystals were successfully grown by the Bridgman method and the luminescence properties is tunable. • The proportion of nonradiative energy transfer from Eu2+ to Sm2+ was improved and the PLQY of Sm2+-related is up to 42.1%. • The fast decay time component of Sm2+ (50 ns) is up to 31.8% for Cs 4 Eu(Br,I) 6 : 3 mol%Sm crystal. • The proposed Sm2+ doped europium -host material principle is an effective method to develop near-infrared (NIR) scintillators for nuclear radiation detection. [ABSTRACT FROM AUTHOR]

Absorption, excitation and emission spectra of cadmium fluoride crystals doped with rare-earth ions were investigated. In contrast to alkaline-earth fluorides the absorption spectra due to 4f - 5d transitions of Ce^3+, Pr^3+ and Tb^3+ ions are broadened. No 5d-4f emissions were observed. These prove that 5d(eg) levels of rare earth ions lie in conduction band of CdF2 crystal. Emission spectra of Tb^3+ show the group of 4f-4f ^5D4-^{7}F_j lines in contrast to other alkaline-earth fluorides where emission due to ^5D3-^{7}F_j transitions is also observed. The absence of the emission is due to position of ^5D3 level within condution band. Among the all measured crystals doped with impurity ions (Pr, Nd, Eu, Ho, Tb, Tm, Yb, Ga, In or Mn), the CdF2 doped with Pr^3+, Tb^3+, or Mn^2+ ions have the highest light outputs under x-ray excitation. [ABSTRACT FROM PUBLISHER]

Photoluminescence, X-ray excited radioluminescence and photoelectron yield characteristics were studied in multicomponent GdGaYAG:Ce and GdGaLuAG:Ce garnet films grown by liquid phase epitaxy. Nonradiative energy transfer from \Gd^3+ to activator \Ce^3+ ions was evidenced. At low Gd doping, < \5\%, two virtually independent emission centers coexist, which compete for intensity: \Ce^3+ with fast 5d-4f emission and \Gd^3+ with slow 4f-4f emission. At higher Gd concentrations, the \Ce^3+ emission retrieves intensity due to the energy transferred from \Gd^3+ donors. At Gd concentration \sim \50\% and above, the \Gd^3+ emission is suppressed due to energy migration and transfer to \Ce^3+ centers. In these samples, the host emission is also completely quenched and the best scintillator performance is achieved. Contrary to melt-grown crystals, no positive role of Ga substitution was found in epitaxial films. [ABSTRACT FROM PUBLISHER]

Results of investigation of energy transfer mechanism in SrF2 crystals doped with Pr^3+ ions are presented. Temperature dependences of 5d-4f and exciton emission in this material under X-ray excitation, and thermostimulated luminescence (TSL) in temperature range 80–300 K are studied. It has been established that in SrF2-Pr^3+ crystals the consecutive electron-hole capture mechanism of energy transfer takes place. Also we found that hole centers made a contribution to energy transfer from primary electrons and holes to Pr^3+ ions. [ABSTRACT FROM PUBLISHER]

Emission and excitation spectra of CaF_2, SrF_2, BaF_2 doped with Nd^3+, Sm^3+, Ho^3+, Er^3+, Tm^3+ excited by vacuum ultraviolet photons or by x-rays were studied. Decay times of the Nd^3+ emission near 180 nm at 7 K were 17.7, 15.3, 12.3 ns in CaF_2, SrF_2, BaF_2 respectively. 4f^n-1 5d^1-4f^n luminescence bands were found at 170–200 nm for Sm^3+ ions and at 140–190 nm for Ho^3+. [ABSTRACT FROM PUBLISHER]

(CexCa1-x)F2+x single crystal with x = 0.0001 - 0.03 were grown by the μ-PD method. Ce3+ doping in CaF2 lattice gives rise to characteristic absorption and emission bands, which are governed by the characteristics of the isolated Ce3+ -Fi- C4v pair centers and small clusters composed from these pairs. With increasing Ce concentration there is a strong increase of the absorption bands related to the cluster centres, but the radioluminescence spectra are always governed by the emission of the isolated Ce3+ -F1- C4v pairs without noticeable changes in the emission band shape. Highest radioluminescence intensity is achieved for Ce0.1{%} concentration and above 1{%} of Ce the onset of concentration quenching is observed. Scintillation response is governed by the energy transfer from the CaF2 host lattice and even for the Ce3{%} sample the dominant scintillation decay time is about 50{%} longer with respect to the photoluminescence decay time of Ce3+ -Fi- C4v pair centres. Energy transfer processes and the role of different Ce3+-based centers are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Emission and excitation spectra and luminescence decay kinetics were studied for Pr3+-doped Lu3Al5O12 and Y3Al5O12 single crystalline films (SCF) grown by the liquid phase epitaxy method from a PbO-based flux. The influence of lead-induced centers on their scintillation characteristics was clarified. It was found that the influence of single Pb2+-based centers on the characteristics of Pr3+ centers due to the Pb2+ →Pr3+ energy transfer was weak. However, an overlap of the emission spectra of single and dimer lead-induced centers with the emission spectrum of Pr3+ ions, and especially a strong overlap of the 4f–5d1 absorption band of Pr3+ ions with the slow emission of localized excitons in the 290nm band had a considerable influence on the scintillation characteristics of the Pr3+-doped SCF. [Copyright &y& Elsevier]