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Pure and Eu2+‐activated fluoroborate BaGaBO3F2 was prepared using high‐temperature solid‐state reaction. BaGaBO3F2 is a wide band semiconductor with the indirect transition characteristic. The excitation and luminescence spectra of the phosphor were measured, and it was found that Eu2+‐activated BaGaBO3F2 exhibits a bright blue color under ultraviolet (UV) light. The narrow emission band peaked at 425 nm is attributed to the transitions of 4f65d→4f7(8S7/2), and the Stokes shift estimated for this phosphor sample is 3140 cm−1. The lifetime of the luminescence is also reported. The absolute quantum efficiency (QE) of the phosphor was evaluated, and it was found that the absolute QE decreases with increasing Eu2+ concentration. The phosphor shows an excellent quantum efficiency of 72.5% and a high thermal activation energy of 0.342 eV. The study concludes that Eu2+‐doped BaGaBO3F2 phosphor has promising luminescence application abilities and can be used as a blue‐emitting phosphor in a variety of applications. [ABSTRACT FROM AUTHOR]

A series of blue phosphors based on Eu2+-activated boracite Zn 3 B 7 O 13 Cl were synthesized by high-temperature solid-state reaction. The phase composition and crystal structure were confirmed by XRD Rietveld refinements, while the optical transitions and band natures were analyzed using absorption spectra. The blue luminescence of Zn 3 B 7 O 13 Cl:Eu2+ shows a narrow band spectrum peaked at 405 nm due to the 4f65 d→4f7(8S 7/2) transitions. Additionally, the sharp line transition of 4f7 (6P 7/2)→4f7 (8S 7/2) was also detected even at 300 K. The experiments confirm that the blue luminescence efficiency of Zn 3 B 7 O 13 (Cl 1-x F x):0.03Eu2+ (x = 0, 0.05, 0.1, 0.2, 0.3) is improved with the increase of the substitution of F− for Cl−. To further improve the luminescence efficiency, the samples were post-annealed at 850 °C in a reducing atmosphere. The results demonstrate that the post-annealing can improve the luminescence efficiency and thermal stability in as-prepared Zn 3 B 7 O 13 (Cl 1-x F x):0.03Eu2+ (x = 0, 0.05, 0.1, 0.2, 0.3) by eliminating the residual Eu3+. The maximum efficiency and thermal activation energy were confirmed in post-annealed Zn 3 B 7 O 13 (Cl 1-x F x):0.03Eu2+ (x = 0.3), which are 65% and 0.31 eV, respectively. The luminescence mechanisms and thermal stability of Eu2+ activators were discussed. • Zn 3 B 7 O 13 Cl:Eu2+ shows an efficient narrowband blue luminescence. • Sharp line transition of 4f7 (6P 7/2).→4f7 (8S 7/2) was also detected even at 300 K. • Luminescence efficiency increases with the substitution of F− for Cl− in the lattice. • Post-annealing eliminates residual Eu3+ resulting in significant improvement of luminescence. [ABSTRACT FROM AUTHOR]

Ce3+/Tb3+ co-doped BaGaBO 3 F 2 is a new rare-earth activated luminescent material with efficient green luminescence. The phosphor was synthesized via the conventional solid-state reaction and characterized by X-ray powder diffraction, photoluminescence, and decay lifetimes. The Ce3+/Tb3+ co-doped phosphor exhibits an efficient excitation between 280 and 420 nm, making it suitable for commercial near-UV chips. The 4f–5d transitions of Ce3+ sensitizer allow the phosphor to be excited by the near-UV light, resulting in green and blue luminescence from Tb3+ and Ce3+, respectively. By controlling Ce3+/Tb3+ doping, the luminescence color can be tuned from blue to green. The effective transfer of excitation energy from Ce3+ to Tb3+ of BaGaBO 3 F 2 was confirmed by the spectral characteristics and decay lifetimes of samples with different doping concentrations. The dipole-quadrupole mechanism is responsible for the efficient energy transfer from Ce3+ to Tb3+, with a critical distance of 11.69 Å. These results demonstrate that Ce3+/Tb3+ co-doped BaGaBO 3 F 2 is an efficient near-ultraviolet (NUV) excitation phosphor with tunable luminescence from blue to green. This material has the potential to be used as a down-conversion phosphor for NUV light-emitting diodes. • Ce3+/Tb3+ co-doped BaGaBO 3 F 2 is a new rare-earth activated material. • Ce3+ acts as a sensitizer to efficiently transfer excitation to activators. • Luminescence color can be tuned from blue to green in BaGaBO 3 F 2 :Ce3+/Tb3+. • It is potential as a down-conversion phosphor for NUV LEDs. [ABSTRACT FROM AUTHOR]

Borotungstate phosphors Gd 2–2x Yb 2x (B 2 WO 9) (x=0, 0.05, 0.1, 0.15, 0.20, 0.25, 0.30) were synthesized using a straightforward high-temperature solid-state reaction method. The structural and luminescent properties of these phosphors were analyzed through X-ray powder diffraction, optical reflectance, excitation, and luminescence spectra. The up-conversion (UC) and downshifting (DS) processes, along with dynamic decay curves, were studied relative to the Yb3+ activator doping concentration. Upon near-UV excitation, a broadband near-IR luminescence (850–1150 nm) was observed from the 2F 5/2 →2F 7/2 transitions in Yb3+ activators facilitated by significant energy transfer (ET) from the WO 6 polyhedra to the Yb3+ activators within the lattices. Additionally, under 980 nm excitation to the 2F 7/2 excitation states of Yb3+, blue cooperative up-conversion luminescence originating from Yb3+ pairs was detected. The mechanism behind this blue up-conversion was elucidated by analyzing decay lifetimes and emission intensity dependence on pump power, revealing that the cooperative de-excitation of adjacent Yb3+-Yb3+ ion pairs drives this process. This investigation introduces a practical approach for developing a novel Yb3+-doped borotungstate phosphor capable of exhibiting both downshifting and up-conversion luminescence. • Yb3+-activated Gd 2 (B 2 WO 9) were synthesized by solid-phase synthesis. • Doping concentration dependent structure and luminescence were discussed. • Efficient near-IR emission of Yb3+ was demonstrated. • Variation of up-conversion luminescence as a function of laser pump power was studied. • Mechanism of blue up-conversion luminescence via Yb3+ pairs has been described. [ABSTRACT FROM AUTHOR]

A series of Mn2+ single‐doped 0.2Gd2O3‐0.2Al2O3‐0.6SiO2 (GAS: xMn2+) glasses with Si3N4 as reducing agent were prepared. The presence of [SiO4‐x] defects and Mn2+ ions was determined from the absorption and excitation spectra of the glasses. With the increase of Mn2+ concentration, the intensity of blue emission decreases, while the intensity of red emission increases. The color coordinate of GAS: 6Mn2+ glass is (0.264, 0.226). The lifetime of the glasses was tested. Under the monitoring of 440 nm, the fast components (τf) are between 17 and 85 μs, and the slow components (τs) are between 200–650 μs. The former belongs to [SiO4‐x] defects, and the latter is [4E(G), 4A1(G)]→6A1(S) transition of Mn2+ ions. Under the monitoring at 630 nm, the τf are between 110 and 300 μs, and the τs are between 680 and 1220 μs, which are due to 4T1(G)→6A1(S) transition of Mn2+ ions and Mn2+ pairs, respectively. The energy transfer mechanism of [SiO4‐x] defect→Mn2+ ions are explained. The efficient [SiO4‐x] defect →Mn2+ ions energy transfer process was demonstrated by time‐resolved photoluminescence, and the energy transfer efficiency is over 85%. The maximum photoluminescence quantum yield (PL QY) of the glasses can reach 15.87%. The thermal activation energy of the glasses was calculated. In addition, X‐ray excited red luminescence spectra and the mechanism of the glasses were investigated. [ABSTRACT FROM AUTHOR]

(Gd,La) 9.33 (SiO 4 ) 6 O 2 :Ce polycrystalline powder with different proportion of Gd/La and Ce concentration was prepared by sol-gel technique, the crystal structure was confirmed by XRD, the luminescence properties were discussed under UV excitation. The energy transfer of Gd-Gd and Gd-Ce have been systematically investigated using luminescence spectra and there are three different types transfer mechanism for different Ce 3+ and La 3+ concentrations. The nonradiative energy transfer mechanism can switch from a short-range exchange mechanism to a longer-range dipole–dipole mechanism through energy migration between donors in heavily La substituted samples. The luminescence thermo-stability and activation energy were also measured and calculated. The luminescence properties and thermo-stability of Gd 9.33 (SiO 4 ) 6 O 2 :Ce polycrystalline were improved, because of La 3+ substitution which lead to the change of the energy transfer mechanism from Gd 3+ to Ce 3+ [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]

Bi4Si3O12\!\!:\!Zn^{2+}(BSO\!:\!Zn) polycrystalline powders were successfully prepared by sol-gel method. X-ray diffraction measurements confirm that the Zn^2+-doped materials are all monophasic solid solution powders. The influences of doping concentration on the photoluminescence and radioluminescence characteristics have been investigated and discussed. The Zn^2+ doped material shows a better light yield than that of undoped material under X-ray excitation. The fluorescence decay time of the optimal material, excited by UV has been aslso measured. The results show that the Zn^2+ ion doping has a positive effect on the light yield of BSO. But the crystal growth and characterizations of BSO:Zn polycrystalline powders prepared deserve further investigations. [ABSTRACT FROM PUBLISHER]

Abstract: A kind of direct white light phosphor Bi4Si3O12:Dy3+ (BSO:Dy3+) was successfully prepared through a sol–gel technique and its luminescence properties were investigated. The white-light emission is assigned to a mixture of three emission peaks located at 460nm, 488nm and 575nm, respectively. The possible process of origin phosphorescence has been discussed and PL spectra under different temperature conditions have also been recorded. The chromaticity color coordinates of BSO:Dy phosphors at different temperatures were calculated. The thermoluminescence curves exhibit two peaks at 400 and 440K in the range of 300–550K, corresponding to the electron traps with depths of 1.225 and 1.527eV individually. The BSO samples co-doped with Dy and Tb were also prepared and their luminescence properties were investigated. This work provides a promising approach for the development of white light phosphors. [Copyright &y& Elsevier]

Abstract: Ce-doped La2Si2O7 (LaPS:Ce) polycrystalline powders were successfully prepared through a sol–gel technique at lower temperature. The X-ray diffraction measurements confirmed that the Ce-doped powders were a kind of monophase solid solution. Photoluminescence, radioluminescence, and decay time characteristics of the prepared powders have been systematically investigated and discussed. It was noticed that the LaPS:Ce material shows an excellent light yield in comparison with commercial Y3Al5O12:Ce (YAG:Ce) powders under X-ray excitation. The LaPS:Ce sample demonstrated a high temperature stability of luminescence yield up to 250°C and a short decay time. Therefore, the LaPS:Ce powder is proposed to be a novel and promising scintillator material. [Copyright &y& Elsevier]

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]

Combinatorial chemistry is employed in the screening of white light emitting phosphors in the system Bi4-xSi3O12:Lnx (Ln: Pr3+, Eu3+, Tb3+, Dy3+, Er3+). [ABSTRACT FROM AUTHOR]

Different B 2 O 3 content was added to Ce3+–doped Gd 2 O 3 –Al 2 O 3 –SiO 2 (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 Si 3 N 4. The excitation and emission spectra show a blue shift with increase of B 2 O 3 content. The photoluminescence quantum yield (PL QY) increases with the increase of B 2 O 3 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 Bi 4 Ge 3 O 12 (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 B 2 O 3 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. [ABSTRACT FROM AUTHOR]

In this work, an anion-alloying strategy using chloride substitution is used to improve the gamma response performance of cutting-edge Cs 2 LiLaBr 6 :Ce single crystal scintillators. Single crystals of Cs 2 LiLa(Br , Cl) 6 :Ce (CLLBC:Ce) with a size of Ф12 mm × 50 mm were successfully grown by the Bridgman method. The effects of chloride substitution amount on crystal structure, band structure, luminescence properties and the scintillation properties were systematically investigated. The light yield and energy resolution of CLLB:Ce were enhanced as the increase of Cl− content. The highest light yield and optimal energy resolution were achieved on the Cs 2 LiLaBr 4 Cl 2 :Ce, about 86% of the commercial LaBr 3 :Ce single crystal and 4.1% at 662 keV. On a basis of the results of first-principle calculation and pure optical method, the band structures of Cs 2 LiLa(Br,Cl):Ce were constructed, indicating a tendency of band-gap to increase as the Cl− content increases. The origin of light yield improvement was also proposed. • The strategy of chloride substitution is used to improve the performance of Cs 2 LiLaBr 6 :Ce single crystal scintillators. • The results of first-principle calculation and pure optical method indicate that the band-gap becomes bigger as the Cl− content increases. • Cs 2 LiLaBr 4 Cl 2 :Ce shows the highest light yield and optimal energy resolution, about 86% of the commercial LaBr 3 :Ce single crystal and 4.1% at 662 keV. • The origin of light yield improvement was also proposed. [ABSTRACT FROM AUTHOR]

Abstract: Cerium-doped lutetium oxyorthosilicate (Lu2SiO5:Ce3+, or shortly LSO:Ce) luminescent ceramic fibers were synthesized by the sol–gel process followed with electrospinning in the present research. Polyvinyl butyral (PVB) was used as a spinnable carrier and anhydrous system availed the efficient generation of the composite fibers. The phase of Lu2SiO5 starts to appear at 1100°C based on XRD analysis. After annealed at 1200°C for 4h, all samples with different cerium doping concentrations show a pure phase of LSO with a well-crystallized structure. The annealed samples retain smooth surfaces and uniform morphologies. LSO:Ce fibers thus prepared exhibit a strong emission peak located at about 403nm, corresponding to the Ce3+ 5d1→4f1 transitions. LSO:1%Ce fibers exhibit the most intense emission among the samples doped with different cerium concentrations, which also present a much stronger emission than that of LSO:1%Ce powders. X-ray excited luminescence (XEL) spectrum shows that LSO:Ce fibers present a considerable scintillation property as well. Short decay time trait was also observed in LSO:Ce fibers due to their microscopic defects at grain boundaries and surfaces. [Copyright &y& Elsevier]

One-dimensional LuSiO:Ce (LPS:Ce) luminescent fibers were prepared by the sol-gel process combined with electrospinning with polyvinyl butyral as polymer in this study. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, thermogravimetric and differential scanning calorimetry, Fourier transform infrared spectroscopy, photoluminescence, and kinetic decays were used to characterize the resulting samples. After calcinated at 1200 °C, pure crystalline phase of LuSiO was obtained with well maintenance of the fiber morphology. The excitation and emission curves of LPS:Ce samples are influenced by cerium-doping concentrations. LPS:0.5%Ce fibers show the most intense emission among the samples. A fast decay time of tens of nanosecond was also observed in LPS:Ce fibers. Furthermore, LPS:0.5%Ce powders and Y co-doped LPS:0.5%Ce fibers were also prepared in a similar way for comparison. As a result, LPS:0.5%Ce fibers present a much stronger emission and higher quantum efficiency than that of LPS:0.5%Ce powders, and a close efficiency compared with YLuSiO:0.5%Ce fibers. In addition, a facile and efficient fiber molding process can be realized to assemble one-dimensional LPS:Ce fibers into three-dimensional (3D) fibers structures with different shapes like bracelet and spool. Such 3D fiber structures are dense enough and well-shaped even if after high temperature calcination. The high performance LPS:Ce fibers and LPS:Ce 3D fibers may have great potential applications for luminescent clad sensors, optoelectronic devices, or scintillating detectors [ABSTRACT FROM AUTHOR]

Orthorhombic (α) SSPbF 2 microcrystal was synthesized by a normal hydrothermal method. The influence of F/Pb ratio and hydrothermal reaction time on the crystal phase of the acquired PbF 2 samples were discussed, and a β to α phase transition was found according to the XRD results. The undoped α-PbF 2 powder showed a broad but weak emission band around 450–570 nm, which was due to (Pb 2 ) 3+ nearest neighbor pair centers. Dy 3+ ion doped α-PbF 2 samples showed main emission bands at 480 nm and 574 nm, which were assigned to the transitions from 4 F 9/2 to 6 H 15/2 and 6 H 13/2 of Dy 3+ , respectively. Furthermore, the morphology and crystalline properties of the undoped and Dy 3+ doped α-PbF 2 microcrystal powder were also discussed carefully. The decay time results combined with the X-ray excitation results suggested that Dy 3+ ion doped α-PbF 2 is a useful scintillating material for high energy physics applications, such as X-ray scintillating panel, etc. [ABSTRACT FROM AUTHOR]