Characterization of mixed halide scintillators: CsSrBrI₂:Eu, CsCaBrI₂:Eu and CsSrClBr₂:Eu

Eu²⁺-doped mixed halide scintillators, CsSrBrI₂, CsCaBrI₂ and CsSrClBr₂ were studied for gamma-ray spectroscopy applications. We grew Ø13 mm single crystals via the vertical Bridgman method using a self-seeded technique and investigated physical and scintillation properties. Single crystal X-ray diffraction and thermal analysis reveal that CsSrBrI₂ and CsSrClBr₂ have orthorhombic crystal structures and melt congruently at 611 °C and 752 °C, respectively, while CsCaBrI₂ has a cubic structure and melts congruently at 671 °C. All three compounds have the typical Eu²⁺ 5d – 4 f single-peak emission centered between 445 and 462 nm with a scintillation decay time of a few microseconds. The optimal Eu²⁺ concentration to maximize the scintillation light yield was determined to be ~7–10%. All three mixed scintillators have an improved energy resolution compared to the non-mixed CsSrI₃:Eu, CsCaI₃:Eu and CsSrBr₃:Eu. The best performing scintillator is CsSrBrI₂:Eu 7% with light yield of 65,300 ph/MeV and energy resolution of 3.4% at 662 keV. Excellent proportional response for a wide range of gamma-ray energies was measured for all three scintillators.