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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]

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]