Crystal growth of a novel and efficient Tl2HfCl6 scintillator with improved scintillation characteristics

Single crystals of a new promising material Tl2HfCl6 were successfully grown by using a modified vertical Bridgman furnace. Various growth conditions were systematically optimized to achieve improved scintillation characteristics. For the first time, the crystalline phase and structure were analyzed using the Rietveld refinement method. The emission and scintillation properties were investigated in detail. The emission peak under X-ray excitation was centered at 398 nm, which was compatible with the quantum efficiency of the conventional photosensors. The scintillation decay time under γ-ray excitation exhibited a major component of 1 μs with the light yield of 32 000 photon per MeV. The improved energy resolution of the grown crystal was measured to be 4.0% at 662 keV. The significant improvement in decay time, light yield and energy resolution over previously reported results was mainly achieved by adopting a systematic approach of material purification. The applicability of this material in various fields was also investigated for the first time by recording the combined radiation of α-particles and γ-rays. These different types of radiations could be sufficiently separated by employing the charge comparison method with a promising figure-of-merit of 2.6. A simulation using Geant4 was also performed for comparing the detection efficiency of Tl2HfCl6 with those of the conventional halide crystal scintillators. Due to its good scintillation performance and pulse shape discrimination capability, this scintillator may be reasonably considered for various applications in the field of radiation detection.