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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]

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]

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]