Luminescence and Energy Transfer in Lu3Al5O12 Scintillators Co-Doped with Ce3+ and Tb3+

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• 作者：Joanna M. Ogieg艂o ; Aleksander Zych ; Konstantin V. Ivanovskikh ; Thomas J眉stel ; Cees R. Ronda ; Andries Meijerink
• 刊名：The Journal of Physical Chemistry A
• 出版年：2012
• 出版时间：August 23, 2012
• 年：2012
• 卷：116
• 期：33
• 页码：8464-8474
• 全文大小：605K
• 年卷期：v.116,no.33(August 23, 2012)
• ISSN：1520-5215

文摘

Lu₃Al₅O₁₂ (LuAG) doped with Ce³⁺ is a promising scintillator material with a high density and a fast response time. The light output under X-ray or 纬-ray excitation is, however, well below the theoretical limit. In this paper the influence of codoping with Tb³⁺ is investigated with the aim to increase the light output. High resolution spectra of singly doped LuAG (with Ce³⁺ or Tb³⁺) are reported and provide insight into the energy level structure of the two ions in LuAG. For Ce³⁺ zero-phonon lines and vibronic structure are observed for the two lowest energy 5d bands and the Stokes鈥?shift (2 350 cm^鈥?) and Huang鈥揜hys coupling parameter (S = 9) have been determined. Tb³⁺ 4f鈥?d transitions to the high spin (HS) and low spin (LS) states are observed (including a zero-phonon line and vibrational structure for the high spin state). The HS鈥揕S splitting of 5400 cm^鈥? is smaller than usually observed and is explained by a reduction of the 5d鈥?f exchange coupling parameter J by covalency. Upon replacing the smaller Lu³⁺ ion with the larger Tb³⁺ ion, the crystal field splitting for the lowest 5d states increases, causing the lowest 5d state to shift below the ⁵D₄ state of Tb³⁺ and allowing for efficient energy transfer from Tb³⁺ to Ce³⁺ down to the lowest temperatures. Luminescence decay measurements confirm efficient energy transfer from Tb³⁺ to Ce³⁺ and provide a qualitative understanding of the energy transfer process. Co-doping with Tb³⁺ does not result in the desired increase in light output, and an explanation based on electron trapping in defects is discussed.