Crystal growth and scintillation properties of Eu-doped Ca(BrxI1–x)2 crystals

Abstract

In this study, solid solutions of Ca(Br,I)2 were prepared to mitigate the cleavage feature of CaI2. Samples were grown using the Bridgman–Stockbarger (BS) method in a quartz ampoule. Eu2+ 4f–5d emissions were observed, peaking at 462–464 nm with a scintillation decay time of around 1000–1500 ns. Eu2%:CaBr0.5I1.5 showed the best light output of 109,000 photons/MeV, and Eu2%:CaBrI showed the best energy resolution (7.9%@662 keV) among the crystals grown. Eu2%:CaBr0.5I1.5 showed the same crystal phase as CaI2 and a strong cleavage feature. In contrast, Eu2%:CaBrI did not exhibit the cleavage feature and was more feasible for mass production as a detector material. Eu-doped CaBrI was the most promising material, not only for applications in the observation of neutrinoless double beta decay, but also other high-energy physics, gamma ray surveys, and gamma camera applications, owing to the optimization of light yield and energy resolution without cleavage.