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This content will become publicly available on November 24, 2016

Title: Band-gap and band-edge engineering of multicomponent garnet scintillators from first principles

Complex doping schemes in R3Al5O12 (where R is the rare-earth element) garnet compounds have recently led to pronounced improvements in scintillator performance. Specifically, by admixing lutetium and yttrium aluminate garnets with gallium and gadolinium, the band gap is altered in a manner that facilitates the removal of deleterious electron trapping associated with cation antisite defects. Here, we expand upon this initial work to systematically investigate the effect of substitutional admixing on the energy levels of band edges. Density-functional theory and hybrid density-functional theory (HDFT) are used to survey potential admixing candidates that modify either the conduction-band minimum (CBM) or valence-band maximum (VBM). We consider two sets of compositions based on Lu3B5O12 where B is Al, Ga, In, As, and Sb, and R3Al5O12, where R is Lu, Gd, Dy, and Er. We find that admixing with various R cations does not appreciably affect the band gap or band edges. In contrast, substituting Al with cations of dissimilar ionic radii has a profound impact on the band structure. We further show that certain dopants can be used to selectively modify only the CBM or the VBM. Specifically, Ga and In decrease the band gap by lowering the CBM, while As and Sbmore » decrease the band gap by raising the VBM, the relative change in band gap is quantitatively validated by HDFT. These results demonstrate a powerful approach to quickly screen the impact of dopants on the electronic structure of scintillator compounds, identifying those dopants which alter the band edges in very specific ways to eliminate both electron and hole traps responsible for performance limitations. Furthermore, this approach should be broadly applicable for the optimization of electronic and optical performance for a wide range of compounds by tuning the VBM and CBM.« less
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Academy of Sciences of the Czech Republic, Prague (Czech Republic)
  3. Thermo-Calc Software Inc., Pittsburgh, PA (United States)
Publication Date:
OSTI Identifier:
1248741
Report Number(s):
LA-UR--15-23403
Journal ID: ISSN 2331-7019; PRAHB2
Grant/Contract Number:
AC52-06NA25396; P204/12/0805
Type:
Accepted Manuscript
Journal Name:
Physical Review Applied
Additional Journal Information:
Journal Volume: 4; Journal Issue: 5; Journal ID: ISSN 2331-7019
Publisher:
American Physical Society
Research Org:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE