The Synthesis,Growth And Luminescence Properties Of Cerium-doped Rare Earth Scintillation Material

The target of this paper is to take explaratory research on new scintillaion materials doped by Ce³⁺ions.The synthesis,growth and luminescence properties of cerium-doped rare-earth scintilla ation material were mainly investigated in this paper.There are four parts included mainly in this work,and the first part is about Cerium-doped Yb₃Al_5-xGa_xO₁₂?x=0,1,2,3,4,5?powders.Cerium-doped Yb₃Al_5-xGa_xO₁₂?x=0,1,2,3,4,5?powders of Ytterbium Aluminum Gallium garnets were synthesized by high temperature solid-state reaction in a carbon reducing atmosphere.The Ytterbium Aluminum Garnets were characterized by X-ray powder diffraction,UV-Vis diffuse reflectance spectra,photoluminescence spectra and decay time curves.Moreover,the substitution effect for the Al³⁺sites with Ga³⁺in0.5at.%Ce:Yb₃Al_5-xGa_xO₁₂?x=0,1,2,3,4,5?garnets were discussed.With the increase of Ga³⁺ion concentration,the 400-450 nm visible absorption peak had blue shift phenomenon,while the absorption peak of 330-350 nm and the absorption band edge of peaks in the range of 210-230 nm red shifted.Furthermore,the short decay times were very short with less than 10 ns due to the Yb³⁺+Ce³⁺?Yb²⁺+Ce⁴⁺charge transfer luminescence.The second part is about Cs₃LaCl₆·3H₂O crystal.Cs₃LaCl₆·3H₂O crystal with the dimension of?4×7×2 mm³ was grown by the simple method of evaporation and cooling crystallization,and the structures were solved by SHELXT?direct method?.Cs3LaCl6·3H2O single crystal were crystallized in the orthorhombic space group Pnma with cell parameters a=21.1556?6??,b=8.6314?2??,c=8.4779?2??,and Z=4.Meanwhile,the optical and scintillation properties of Cs₃LaCl₆·3H₂O crystal at room temperature were also studied and discussed in this paper.The Cs₃LaCl₆·3H₂O single crystal were characterized by X-ray excited emission?XEL?spectra,photoluminescence spectra and decay time curves.It was found that PL and XEL spectra of Cs₃LaCl₆·3H₂O crystal had the same emission peak of 334 nm.And the luminescence properties were mainly ascribed to self-trapped exciton?STE?luminescence of Cs₃LaCl₆·3H₂O crystal.The third part is about 15at.%Ce:Cs₃LaCl_6-x-x Br_x?x=0,1,2,3,4,5?mixed crystal,this crystals were grown by vertical Bridgman technique.15at.%Ce:Cs3LaCl6-xBrx?x=0,1,2,3,4,5?mixed crystal phase were analyzed by powder XRD characterization,and the results were similar as the standard PDF cards of Cs₃LaCl₆ and Cs₃LaBr₆ compounds,which were proved the synthesis of 15at.%Ce:Cs₃LaCl_6-xBr_x?x=0,1,2,3,4,5?mixed crystals.The structure of 15at.%Ce:Cs₃La Cl_6-xBr_x?x=0,1,2,3,4,5?mixed crystals were monoclinic system,space group C2/c.The scintillation properties of these crystals such as photoluminescence spectrum,X-ray exicted emission spectra and decay times were studied in this work.The decay time were fitted by double exponential.However,the decay times of 15%Ce:Cs₃LaCl₃Br₃ and 15at.%Ce:Cs₃LaClBr₅ crystals are the fastest,the decay times of 15at.%Ce:Cs3LaCl2Br4 are a little slower,the decay times of15at.%Ce:Cs₃LaCl₄Br₂,15at.%Ce:Cs₃LaCl₅Br and 15at.%Ce:Cs₃LaCl₆ crystal are the slowest.The reason for difference of decay times were attributed to the luminescence of self-trapped exciton and Ce³⁺ion.Whether the presence of core valence luminescence or not in the crystals need to be further studied.The fourth part is about pure and Cerium-doped Cs₃LaCl₆ and Cs₃LaBr₆ crystals.These crystals were also grown by vertical Bridgman technique,and as-grown crystals were partially transparent.In addition,cerium-doped Cs3LaCl6 crystals were also reported in the part.X-ray excited emission spectra of Ce:Cs3LaCl6 crystals have the emission peak which were corresponded to the 5d?4f level transition of Ce³⁺ion.The photoluminescence spectra showed that the emission spectra of pure Cs₃LaCl₆ crystals almost no emission peak were observed at about 330 nm.However,the emission spectra of cerium-doped Cs₃LaCl₆ crystal not only had the characteristic peaks of Ce³⁺ion,but also had emission peak about 330 nm.