Latest Progress on Advanced Bridgman Method-Grown K₂PtCl₆ Cubic Structure Scintillator Crystals

We are reporting on the latest growth and scintillating properties of a recently discovered intrinsic scintillating compound with the K ₂ PtCl ₆ simple cubic crystal structure: the Cs-based Cs ₂ HfCl ₆ (CHC) and Cs ₂ HfCl ₄ Br ₂ (CHCB), both with the density of 3.9 g/cm ³ , as well as the Tl-based Tl ₂ HfCl ₆ (THC) and Tl ₂ ZrCl ₆ (TZC). This article presents a successfully developed process of growing crack-free, single crystals of 16 mm diameter to 1-in-diameter CHC by the Bridgman method. The energy resolution of 2.8% [full-width at half-maximum (FWHM)] at 662 keV has been obtained for small diameters and typical 3.5% (FWHM) at 662 keV has been obtained for 1 in × 1 in CHC. The light yield of 30 000 ph/MeV and the 3.8μs primary decay time have been measured for CHC. CHC's excellent linear response to gamma rays compared to those of NaI:Tl and BGO is also reported. The mixed-halides CHC-based compound CHCB performs with a shorter primary decay time of 1.8 μs. Introducing Tl, a heavier element than Cs, increases both Zeff and density of THC and TZC, and improves gamma-ray detection efficiency. Primary decay times are also reduced to about 1 μs for THC and 2 μs for TZC.