Abstract: The ø7 mm undoped Cs₂HfCl₆ and Cs₂HfCl₆∶0.2%Tl(mole fraction) single crystals were grown by the Vertical Bridgman method. The phase, impurities concentrations, luminescence and scintillation properties of crystal samples were studied. Both crystalsbelong to the cubic crystal structure and the space group of Fm3m. When excited by ultraviolet light and X-ray, both crystals exhibit an emission peak at 380 nm originated from self-trapped excitons emission, and Cs₂HfCl₆∶0.2%Tl crystal exhibits an extra Tl⁺ sp-s² transition induced emission at 505 nm. Cs₂HfCl₆ and Cs₂HfCl₆∶0.2%Tl possess high light yields of 37 000 photons/MeV and 36 500 photons/MeV respectively and both have excellent energy resolutions of 3.5% at 662 keV under excitation of ¹³⁷Cs source. The scintillation decay time of undoped Cs₂HfCl₆ is comprised of 0.37 μs (4.2%), 4.27 μs (78.9%) and 12.52 μs (16.9%). The scintillation decay time of Cs₂HfCl₆∶0.2%Tl is comprised of 0.33 μs (3.5%), 4.09 μs (81.9%) and 10.42 μs (14.5%).

Key words: Cs₂HfCl₆∶Tl, self-trapped exciton emission, sp-s² transition, scintillation crystal, Bridgman method, energy resolution