Study On Growth And Scintillation Properties Of Cs₄SrI₆:Eu Crystal

Cs₄SrI₆:Eu crystal is a novel scintillation crystal discovered in recent years.It is reported that its light output at 662 ke V is 60000 ph/Me V(?8 mm³ crystal),the energy resolution is 3.3%,and the scintillation performance is excellent.Its main raw material is Cs I,and its melting point is only 533°C,so there is a huge cost advantage.Cs₄SrI₆ crystal has a K₄Cd Cl₆ structure and belongs to the R-3C space group.The size of the crystals currently studied on Cs₄SrI₆ is relatively small and cannot be put into practical use.There is no research on the growth of large-size crystals at home and abroad.In this paper,after several rounds of experimental investigations,we used the Bridgeman method to grow a 1-inch diameter Cs₄SrI₆:3%Eu crystal.The segregation coefficient of Eu²⁺ions in the crystal was calculated for the first time.The crystal has Eu²⁺as the light-emitting center.There is obvious self-absorption phenomenon,which limits the light-emitting performance of the crystal.This article carried out a series of growth experiments,explored the influencing factors of Cs₄SrI₆:Eu crystal self-absorption.Then we studied the effect of temperature on the fluorescence performance of crystals.The specific research results are summarized as follows:(1)We use a single-tube crystal growth furnace to obtain 0.5-inch diameter Cs₄SrI₆crystals and Cs₄SrI₆:x%Eu crystals.The fluorescence and scintillation properties of these crystals were characterized.(2)A 1-inch diameter Cs₄SrI₆:3%Eu crystal was successfully grown using a single-tube crystal growth furnace,and the whole appeared light green.The fluorescence spectrum shows that the emission peak of the crystal is located at 460 nm,and the excitation spectrum is a broad peak of 270 nm?450 nm.The light output of a 360mm³ volume crystal sample under the?-ray of ¹³⁷Cs@662 ke V is 42000 ph/Me V,and the energy resolution is 7.3%.The decay time ofgrays is 1.86ms.The FAAS method was used to measure the Eu²⁺ion concentration at different positions on a 1-inch diameter crystal,and the segregation coefficient of Eu²⁺in the Cs₄SrI₆ crystal was calculated.Its value was 1.136.(3)The results of temperature-varying fluorescence spectrum show that the emission intensity of Cs₄SrI₆:Eu crystal decreases with increasing temperature,and the half-width FWHM of the emission peak becomes wider with increasing temperature.This shows that the lattice vibration increases after the temperature rises,and the exciton-phonon interaction(38)_LO occupies a dominant position((38)_LO=923 me V).We calculated the thermal activation energy of the crystal (35)E=0.05 e V.(4)The comparison of the performance of the crystals grown at different concentrations shows that the self-absorption of the crystals increases with the increase of the Eu²⁺doping concentration,resulting in a decrease in performance.Our experimentally grown Sm²⁺co-doped Cs₄SrI₆:3%Eu:0.5%Sm crystal test results show that the performance of the crystal is effectively enhanced and the phenomenon of self-absorption is suppressed.It shows that the co-doping of Sm²⁺ is a feasible method to solve the self-absorption problem of Cs₄SrI₆:Eu crystal.