Crystal growth and Ce³⁺ concentration optimization in Tl₂LaCl₅: An excellent scintillator for the radiation detection

High effective atomic number (70) and density (5.17 g/cm³) among the known halide scintillators with excellent scintillation performance make Tl₂LaCl₅ (TLC) a new potential candidate for X- and γ-ray detection. The preliminary scintillation performance of TLC was reported earlier for small crystal pieces without any detail information of synthesis, crystal growth optimization conditions and Ce³⁺ doping concentration, which are investigated in this study. The newly developed melt rotation technique was found to be the best one for the synthesis of TLC and probably for other Tl-based compounds among the known melting techniques. Pure and nominal Ce³⁺ concentration of 1%, 3%, 5%, 7% and 10% TLC crystals were grown with two zones vertical Bridgman technique in two different type of homemade furnaces and found the optimum thermal gradient, pulling and cooling rate as 25 °C/cm, 0.5 mm/h and 20 °C/h, respectively. The best energy resolution of ∼3.3% (FWHM) and light yield of ∼82,000 ph/MeV were obtained for TLC:3%Ce³⁺ under 662 keV γ-rays excitation. The promising scintillation performance of TLC revealed that this crystal could be used in Positron Emission Tomography (PET), environmental radiation monitoring and homeland security applications.