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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Luminescence and energy transfer in Lu _3Al _5O _(12) scintillators co-doped with Ce ~(3+) and Tb ~(3+)
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Luminescence and energy transfer in Lu _3Al _5O _(12) scintillators co-doped with Ce ~(3+) and Tb ~(3+)

机译：Ce〜（3+）和Tb〜（3+）共掺杂的Lu _3Al _5O _（12）闪烁体的发光和能量转移

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摘要

Lu _3Al _5O _(12) (LuAG) doped with Ce ~(3+) is a promising scintillator material with a high density and a fast response time. The light output under X-ray or γ-ray excitation is, however, well below the theoretical limit. In this paper the influence of codoping with Tb ~(3+) is investigated with the aim to increase the light output. High resolution spectra of singly doped LuAG (with Ce ~(3+) or Tb ~(3+)) are reported and provide insight into the energy level structure of the two ions in LuAG. For Ce ~(3+) zerophonon lines and vibronic structure are observed for the two lowest energy 5d bands and the Stokes' shift (2 350 cm ~(-1)) and HuangRhys coupling parameter (S = 9) have been determined. Tb ~(3+) 4f-5d transitions to the high spin (HS) and low spin (LS) states are observed (including a zerophonon line and vibrational structure for the high spin state). The HS-LS splitting of 5400 cm ~(-1) is smaller than usually observed and is explained by a reduction of the 5d-4f exchange coupling parameter J by covalency. Upon replacing the smaller Lu ~(3+) ion with the larger Tb ~(3+) ion, the crystal field splitting for the lowest 5d states increases, causing the lowest 5d state to shift below the 5D4 state of Tb ~(3+) and allowing for efficient energy transfer from Tb ~(3+) to Ce ~(3+) down to the lowest temperatures. Luminescence decay measurements confirm efficient energy transfer from Tb ~(3+) to Ce ~(3+) and provide a qualitative understanding of the energy transfer process. Codoping with Tb ~(3+) does not result in the desired increase in light output, and an explanation based on electron trapping in defects is discussed.
机译：掺杂有Ce〜（3+）的Lu _3Al _5O _（12）（LuAG）是一种有前途的闪烁体材料，具有高密度和快速响应时间。但是，在X射线或γ射线激发下的光输出远低于理论极限。本文研究了共掺杂对Tb〜（3+）的影响，旨在增加光输出。报告了单掺杂LuAG（具有Ce〜（3+）或Tb〜（3+））的高分辨率光谱，并提供了对LuAG中两个离子能级结构的了解。对于Ce〜（3+）零声子线和振动子结构，观察到两个最低能量的5d谱带，并确定了斯托克斯位移（2 350 cm〜（-1））和HuangRhys耦合参数（S = 9）。观察到Tb〜（3+）4f-5d转变为高自旋（HS）和低自旋（LS）态（包括零声子线和高自旋态的振动结构）。 5400 cm〜（-1）的HS-LS分裂比通常观察到的要小，并且可以通过5d-4f交换耦合参数J的共价降低来解释。在用较大的Tb〜（3+）离子替换较小的Lu〜（3+）离子后，对于最低5d态的晶体分裂增加，导致最低5d态移动到Tb〜（3+）的5D4态以下。 ）并允许从Tb〜（3+）到Ce〜（3+）的能量有效转移至最低温度。发光衰减测量结果证实了从Tb〜（3+）到Ce〜（3+）的有效能量转移，并提供了对能量转移过程的定性理解。与Tb〜（3+）共掺杂不会导致所需的光输出增加，并且将讨论基于缺陷中电子陷阱的解释。

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