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Title: Atomistic scale investigation of cation ordering and phase stability in Cs-substituted Ba 1.33Zn 1.33Ti 6.67O 16, Ba 1.33Ga 2.66Ti 5.67O 16 and Ba 1.33Al 2.66Ti 5.33O 16 hollandite

Abstract

The titanate-based hollandite structure is proposed as an effective ceramic waste form for Cs-immobilization. In this study, quantum-mechanical calculations were used to quantify the impact of A-site and B-site ordering on the structural stability of hollandite with compositions Ba xCs y(M zTi 8-z)O16, where M = Zn 2+, Ga 3+, and Al 3+. The calculated enthalpy of formation agrees with experimental measurements of related hollandite phases from melt solution calorimetry. Ground state geometry optimizations show that, for intermediate compositions (e.g., CsBaGa 6Ti 18O 48), the presence of both Cs and Ba in the A-site tunnels is not energetically favored. However, the decay heat generated during storage of the Cs-containing waste form may overcome the energetics of Ba and Cs mixing in the tunnel structure of hollandite. The ability of the hollandite structure to accommodate the radioparagenesis of Cs to Ba is critical for long term performance of the waste. For the first time, B-site ordering was observed along the tunnel direction ([001] zone axis) for the Ga-hollandite compositions, as well as the intermediate Al-hollandite composition. These compositionally dependent structural features, and associated formation enthalpies, are of importance to the stability and radiation damage tolerance of ceramic waste forms.

Authors:
 [1];  [1];  [1];  [1]
  1. Clemson Univ., SC (United States)
Publication Date:
Research Org.:
Clemson Univ., SC (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1500029
Grant/Contract Number:  
SC0012530
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 8; Journal Issue: 1; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Wen, Yi, Xu, Yun, Brinkman, Kyle S., and Shuller-Nickles, Lindsay. Atomistic scale investigation of cation ordering and phase stability in Cs-substituted Ba1.33Zn1.33Ti6.67O16, Ba1.33Ga2.66Ti5.67O16 and Ba1.33Al2.66Ti5.33O16 hollandite. United States: N. p., 2018. Web. doi:10.1038/s41598-018-22982-7.
Wen, Yi, Xu, Yun, Brinkman, Kyle S., & Shuller-Nickles, Lindsay. Atomistic scale investigation of cation ordering and phase stability in Cs-substituted Ba1.33Zn1.33Ti6.67O16, Ba1.33Ga2.66Ti5.67O16 and Ba1.33Al2.66Ti5.33O16 hollandite. United States. doi:10.1038/s41598-018-22982-7.
Wen, Yi, Xu, Yun, Brinkman, Kyle S., and Shuller-Nickles, Lindsay. Thu . "Atomistic scale investigation of cation ordering and phase stability in Cs-substituted Ba1.33Zn1.33Ti6.67O16, Ba1.33Ga2.66Ti5.67O16 and Ba1.33Al2.66Ti5.33O16 hollandite". United States. doi:10.1038/s41598-018-22982-7. https://www.osti.gov/servlets/purl/1500029.
@article{osti_1500029,
title = {Atomistic scale investigation of cation ordering and phase stability in Cs-substituted Ba1.33Zn1.33Ti6.67O16, Ba1.33Ga2.66Ti5.67O16 and Ba1.33Al2.66Ti5.33O16 hollandite},
author = {Wen, Yi and Xu, Yun and Brinkman, Kyle S. and Shuller-Nickles, Lindsay},
abstractNote = {The titanate-based hollandite structure is proposed as an effective ceramic waste form for Cs-immobilization. In this study, quantum-mechanical calculations were used to quantify the impact of A-site and B-site ordering on the structural stability of hollandite with compositions BaxCsy(MzTi8-z)O16, where M = Zn2+, Ga3+, and Al3+. The calculated enthalpy of formation agrees with experimental measurements of related hollandite phases from melt solution calorimetry. Ground state geometry optimizations show that, for intermediate compositions (e.g., CsBaGa6Ti18O48), the presence of both Cs and Ba in the A-site tunnels is not energetically favored. However, the decay heat generated during storage of the Cs-containing waste form may overcome the energetics of Ba and Cs mixing in the tunnel structure of hollandite. The ability of the hollandite structure to accommodate the radioparagenesis of Cs to Ba is critical for long term performance of the waste. For the first time, B-site ordering was observed along the tunnel direction ([001] zone axis) for the Ga-hollandite compositions, as well as the intermediate Al-hollandite composition. These compositionally dependent structural features, and associated formation enthalpies, are of importance to the stability and radiation damage tolerance of ceramic waste forms.},
doi = {10.1038/s41598-018-22982-7},
journal = {Scientific Reports},
issn = {2045-2322},
number = 1,
volume = 8,
place = {United States},
year = {2018},
month = {3}
}

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Works referenced in this record:

Generalized Gradient Approximation Made Simple
journal, October 1996

  • Perdew, John P.; Burke, Kieron; Ernzerhof, Matthias
  • Physical Review Letters, Vol. 77, Issue 18, p. 3865-3868
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Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides
journal, September 1976