Crystal Growth And Scintillation Properties Of Undope And Ce³⁺-doped GdI₃ Crystals

Gadolinium iodide doped with Cerium ?GdI₃:Ce? scintillator exhibits many excellent features that include high density, high effective Z, high light output, high energy resolution,short decay time and so on. The isotopes 157Gd and 155Gd in Gd-based compounds have extremely high cross-section for thermal neutrons which is 20 times larger than that of the tradition 3He, 10B, 7Li-based detectors. Therefore, GdI₃:Ce crystal is considered as one of candidates for neutron detection, nuclear physics, environmental monitoring, high-energy physics, medical application.Different Ce-doped concentration GdI₃:?%Ce ??=0,0.5,1,2? crystals have been grown by vertical Bridgman method in evacuated quartz crucibles in this study. Crystal ingots with a diameter of 15mm and a length of 40mm were successfully grown, and then after being cut and polished, the samples without crack and inclusion were obtained. The influence of growth parameters on crystal quality and cracking was investigated, such as furnace temperatures,growth rates and crucible shapes. Considering the low hardness and easy deliquescence, an effective encapsulation method was developed. At last, we studied the spectrum and scintillation properties of as-grown crystals.The experiment results indicate that the transparent crystal without crack and inclusion can be grown when the temperature zone of furnace was set 1020?, the temperature gradient of interface between solid and melt was kept about 40±5?/cm, the solidification rate was set 0.4mm/h,the cooling rate was set 7 ?/h and a length of 20mm twist capillary tip was acted as a seed. The tests shows that the spectra of GdI₃:Ce exhibit a broad emission band ?450-700nm?peaking at 550nm under X-rays or ultraviolet excitation. All the GdI₃:Ce crystal samples have only one component of the decay time constant under y rays and the decay time gets faster while the Ce-doped concentration gets higher. The energy resolution of GdI₃:2%Ce could be as high as 3.4% at 662keV ? rays,and GdI₃:Ce crystals are promising detection materials for thermal neutron.