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Role of Lithium Codoping in Enhancing the Scintillation Yield of Aluminate Garnets
Physical Review Applied ( IF 4.6 ) Pub Date : 2020-06-25 , DOI: 10.1103/physrevapplied.13.064060
Yuntao Wu , Ge Yang , Dan Han , Ming Liu , Ayman Hawari , Mao-Hua Du , Jing Peng , Camera Foster , Shiyou Chen , Merry Koschan , Charles L. Melcher

The aim of this work is to clarify the scintillation-yield enhancement in LuYAG:Pr scintillators obtained by Li codoping via integrated study of the valence state of activators, the preferential site occupancy of Li codopants, and defect structures from experimental and theoretical insights. With Li codoping, the light yield and energy resolution of 10×10×10mm3 LuYAG:Pr samples are improved from 15 600 to 24 800 photons/MeV, and 5.3 to 4.3% at 662 keV, respectively. The optical absorption spectra indicate that Li codoping does not induce conversion of stable Pr3+ to Pr4+ in LuYAG:Pr single crystals. Based on the formation energies of substitutional and interstitial Li sites using density-functional-theory (DFT) calculations and the 7Li nuclear magnetic resonance results, it is shown that the Li ions prefer to dominantly occupy the fourfold coordinated interstitial sites and fourfold coordinated Al sites. The systematic analysis of thermoluminescence glow curves, positron annihilation lifetime spectroscopies, and defect formation energies derived from DFT calculations reveals that the concentration of isolated Lu and Al vacancies as dominant acceptor defects is reduced by Li codoping, whilst the shallow Lii interstitial defects and the deep VO oxygen vacancies are introduced simultaneously. We propose that the lowering of hole trapping at defects resulting from Li codoping contributes to the scintillation-yield enhancement.

中文翻译:

锂共掺杂在提高铝酸盐石榴石闪烁产量中的作用

这项工作的目的是阐明闪烁体的产量提高。 YAG 通过获得的闪烁体 通过对激活剂价态,优先位点占据率的综合研究进行共掺杂 实验和理论上的洞察力,以及缺陷结构。用 共掺杂,光的产量和能量分辨率 10×10×10毫米3 YAG样品分别从15600光子/ MeV提高到24800光子/ MeV,在662keV时分别提高5.3%至4.3%。光学吸收光谱表明 共掺杂不会诱导稳定的转化 3+4+YAG单晶。基于替代和间隙的形成能 使用密度泛函理论(DFT)的计算和 7 核磁共振结果表明, 离子倾向于占据四重配位间隙位点和四重配位间隙位点 网站。根据DFT计算得出的热致发光辉光曲线,正电子an没寿命光谱和缺陷形成能的系统分析表明, 作为主要受体缺陷的空位减少了 共掺杂,而浅层 一世 间隙缺陷和深层 VØ同时引入氧空位。我们建议降低由于 共掺杂有助于闪烁产量的提高。
更新日期:2020-06-25
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