零维钙钛矿结构Cs3Cu2Br5单晶的生长和X射线探测性能

金属卤化物低维钙钛矿具有高效的发光性能,并且作为闪烁体在辐射探测领域表现出极大的潜力。本文采用布里奇曼坩埚下降法生长出全无机零维钙钛矿结构Cs₃Cu₂Br₅单晶。研究了Cs₃Cu₂Br₅的光学吸收、光致激发和发射,时间分辨光致发光和以及X射线探测性能。Cs₃Cu₂Br₅晶体结构为正交晶系,空间群为Pnma。在X射线激发下,Cs₃Cu₂Br₅晶体具有峰值约为467 nm的宽带发射,该发射来自自陷激子发射。Cs₃Cu₂Br₅的稳态光产额约为4 000 ph./MeV,且X射线余辉性能表现与BGO晶体相当。     

Active Loss of Light Yield of PbWO4：Y Scintillation Crystals After Irradiation

PWO crystals doped with yttrium were grown with the Bridgman method in platinum crucible and by using an indigenously developed resistive heating furnace. After an exposure of γ-ray from a ^60Co source, with the dose rate of lS rad/h for 20h, the light output increases for about 15%, accompanied with vanishing of an optical absorption band at 420 nm. The excitation and emission spectra of PWO crystals were measured before and after irradiation with different dose rates. The optical absorption band at 420nm was also found in the PWO sample annealed in oxygen-rlch atmosphere. It is suggested that the absorption band at 42Onm is related to Pb^3 point defects existing in the PWO crystal. The unusual change of light output after irradiation probably results from the transformation of lead ions from Pb^3 to Pb^2 .     

LnX3型稀土卤化物闪烁晶体的闪烁性能

本文简要综述了LnX3型稀土卤化物闪烁晶体的发展历史与研究现状,对几种常见晶体(CeF3,LaF3,LuCl3,LaCl3,LuBr3,LaBr3)的物理、化学性质、晶体生长及闪烁性能等进行详细总结归纳,同时指出了当前具有优异闪烁性能的LaCl3:Ce和LaBr3:Ce晶体亟待解决的问题、未来的发展方向及其广阔的应用前景.     

Gd3(Al,Ga)5O12:Ce闪烁晶体缺陷对其发光性能的影响

新型闪烁晶体Gd₃(Al,Ga)₅O₁₂:Ce(GAGG:Ce)在制备过程中易出现包裹体及反格位缺陷等问题,严重影响晶体的性能.为了抑制这些缺陷以得到大尺寸高质量的GAGG:Ce晶体,本文以Gd₃(Al,Ga)₅O₁₂为基质、Ce3+为掺杂离子,采用提拉法生长得到了GAGG:Ce晶体,并对不同晶体部位的物相结构、微区成分、透光性质、发光及时间性能进行了测试和对比分析.结果表明,GAGG:Ce晶体的透过谱中存在340和440 nm两处Ce³⁺特征吸收带,且位于550 nm处的直线透过率为82%.晶体尾部因杂相包裹体等宏观缺陷的影响,导致其透过率下降至70%左右.微区成分分析进一步表明GAGG:Ce晶体中存在三种类型的包裹体,分别为富Gd相、富Ce相及(Al,Ga)₂O₃相.GAGG:Ce晶体的X射线激发发射谱中在550 nm附近存在Ce³⁺宽发射带,且380 nm处还存在GdAl/Ga反格位缺陷引起的发射.晶体中存在的杂相包裹体及GdAl/Ga反格位缺陷等因素导致Ce³⁺在GAGG基质的发光强度下降12.5%;GdAl/Ga反格位离子与近邻Ce的隧穿效应使得GAGG:Ce晶体的衰减时间由117.7 ns延长至121.9 ns,且慢分量比例由16%增加至17.2%.