Tl2HfCl6 and Tl2ZrCl6: Intrinsic Tl-, Hf-, and Zr-based scintillators

•Tl-, Hf- and Zr-based scintillator crystals with high density and high light yield.•Intrinsic scintillator crystals with simple cubic crystal structures.•Energy resolutions below 3.8% at 662 keV and good proportional responses to photon energies. The re-discovery of Cs2HfCl6 (CHC) as a scintillator has lately generated much interest in this material and its family, which belongs to the K2PtCl6 cubic crystal structure [1]. CHC is an intrinsic scintillator that is non-hygroscopic, has no self-radioactivity, provides good energy resolution, and has good non-proportionality. In this paper we are reporting growth and scintillation properties of two new and Tl-, Hf- and Zr-based compounds of Tl2HfCl6 and Tl2ZrCl6, with physical densities of 5.1 g/cm3 and 4.5 g/cm3, respectively and effective atomic numbers (Zeff) of 71 and 69, respectively. Samples from successfully grown 16 mm diameter boules were cut, processed, and characterized for their scintillation and radiometric properties. Energy resolutions of 3.7% (FWHM) for THC and 3.4% for TZC (FWHM) at 662 keV are measured. Primary luminescence decay times of 1.1 μs and 2.3 μs, for Tl2HfCl6 and Tl2ZrCl6, respectively, as well as good proportionality for both materials have been observed.