Large-Diameter Growth of Thallium-Based Ternary Halide Tl2HfX6 and Tl2ZrX6: Intrinsic Bright Scintillators for Detection and Imaging

The search for new bright scintillators with performance close to ideal is the target for many research centers worldwide. This paper presents advanced bright thallium (Tl)-based K2PtCl6-type intrinsic scintillators for detection and imaging applications. Dopant-free Tl-based compounds of Tl2HfX6 and Tl2ZrX6 (X = Cl, Br, or mixed halogens) that were investigated, grown, and published previously are now scaled up to one-inch-diameter crystals. Energy resolutions of 4.1% for Tl2HfCl6, 4.4% for Tl2ZrCl6, 4.8% for Tl2Hf(Cl,Br)6, and 4.1% for Tl2Zr(Cl,Br)6, as well as light yields of 22,300 ph/MeV for Tl2HfCl6, 38,500 ph/MeV for Tl2ZrCl6, 19,000 ph/MeV for Tl2Hf(Cl,Br)6, and 39,900 ph/MeV for Tl2Zr(Cl,Br)6, are measured. These crystals have generally linear responses to gamma-rays above 100 keV. Because of their many favorable attributes, these novel crystals will be beneficial in many gamma-ray detector applications that require better physical densities, Zeff values, energy resolutions, and relative detection efficiency than NaI:Tl, without the constraints of light yield and decay time constants.