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Title: Role of Ce 4 + in the scintillation mechanism of codoped Gd 3 Ga 3 Al 2 O 12 : Ce

To control the time-response performance of widely used cerium-activated scintillators in cutting-edge medical-imaging devices, such as time-of-flight positron-emission tomography, a comprehensive understanding of the role of Ce valence states, especially stable Ce 4+, in the scintillation mechanism is essential. However, despite some progress made recently, an understanding of the physical processes involving Ce 4+ is still lacking. The aim of this work is to clarify the role of Ce 4+ in scintillators by studying Ca 2+ codoped Gd 3Ga 3Al 2O1 2∶Ce (GGAG∶Ce). By using a combination of optical absorption spectra and x-ray absorption near-edge spectroscopies, the correlation between Ca 2+codoping content and the Ce 4+ fraction is seen. The energy-level diagrams of Ce 3+ and Ce 4+ in the Gd 3Ga 3Al 2O 12 host are established by using theoretical and experimental methods, which indicate a higher position of the 5d 1 state of Ce 4+ in the forbidden gap in comparison to that of Ce 3+. Underlying reasons for the decay-time acceleration resulting from Ca 2+ codoping are revealed, and the physical processes of the Ce 4+-emission model are proposed and further demonstrated by temperature-dependent radioluminescence spectra under x-ray excitation.
Authors:
 [1] ;  [2] ;  [3] ;  [2] ;  [2]
  1. Univ. of Tennessee, Knoxville, TN (United States); Chinese Academy of Science, Shanghai (China)
  2. Univ. of Tennessee, Knoxville, TN (United States)
  3. Wake Forest Univ., Winston-Salem, NC (United States)
Publication Date:
Grant/Contract Number:
AC02-05CH1123
Type:
Publisher's Accepted Manuscript
Journal Name:
Physical Review Applied
Additional Journal Information:
Journal Volume: 2; Journal Issue: 4; Related Information: CHORUS Timestamp: 2017-04-06 12:08:58; Journal ID: ISSN 2331-7019
Publisher:
American Physical Society
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
OSTI Identifier:
1180297