Optimized Bridgman growth of Cs2LiYCl6:Ce single crystals and energy resolution improvement by codoping

Abstract

Cs2LiYCl6:Ce is a novel scintillation crystal with good energy resolution, high light yield, and outstanding neutron/gamma discrimination capability. However, its complex composition and incongruent melting behavior pose many challenges to the crystal growth. In this study, five different compositions of Cs2LiYCl6:Ce crystals were grown using the vertical Bridgman method. These compositions included LiCl at 57 mol%, 60 mol%, and 63 mol%, as well as CsCl and YCl3 at ratios of 1.9:1 and 2.1:1. It was found that the highest CLYC phase volume fraction could be obtained in the recipe with a LiCl composition of 60 mol%, while changing the ratio of CsCl to YCl3 did not show any significant positive effect on crystal growth. In addition, Ca2+/Sr2+ was applied to modify the scintillation performance of CLYC:Ce. A batch of Φ11mm crystals with different co-doping concentrations of Ca2+ and Sr2+ were successfully grown by using the Multi-ampoule Bridgman method, no cracks or inclusions were observed in the grown crystals. Co-doping showed little effect on the radiation luminescence and transmittance spectra of CLYC. The scintillation decay curves demonstrated that the decay times depend on the co-doping concentration. Most notably, the energy resolution of CLYC:Ce is improved from 4.6 % to 3.8 % by co-doping 0.05 % Sr2+ under 662 keV gamma-ray excitation. However, the light yield is reduced because of co-doping of Ca2+ and Sr2+, especially Ca2+ having a more pronounced effect.