Investigation of CeBr3-xIx scintillators

CeBr3 is an intrinsic scintillator that has promising performance capabilities such as 60,000 ph/MeV and similar to 4% energy resolution at 662 keV. It has been shown that halide mixing can improve the light yield of single halide scintillators. In this work we attempted to improve on CeBr3 by creating a mixed halide composition CeBr3-xIx. Analysis of melt-freeze samples revealed that the light yield of CeI3 rapidly increases as bromine is substituted. Thirteen mm diameter crystals were grown using the vertical Bridgman technique, with x values between 0.03 and 1. The CeBr2.5I0.5 crystal segregated into two sections, colorless and green, while the CeBr2I crystal was entirely green. X-ray diffraction analysis was used to identify the two phases. Decay time increased as iodine concentration increased. All colorless phase crystals reached < 4.5% energy resolution at 662 keV and > 65,000 ph/MeV, with the CeBr2.94I0.06 crystal achieving 3.9% energy resolution at 662 keV. The green phase crystals both reached light yields of 78,000 ph/MeV, the highest ever recorded for a CeI3 phase crystal.