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Title: Charge-Coupled Substituted Garnets (Y3-xCa0.5xM0.5x)Fe5O12 (M = Ce, Th): Structure and Stability as Crystalline Nuclear Waste Forms

Abstract

The garnet structure has been proposed as a potential crystalline nuclear waste form for accommodation of actinide elements, especially uranium (U). In this study, yttrium iron garnet (YIG) as a model garnet host was studied for the incorporation of U analogs, cerium (Ce) and thorium (Th), incorporated by a charge-coupled substitution with calcium (Ca) for yttrium (Y) in YIG, namely, 2Y3+ = Ca2+ + M4+, where M4+ = Ce4+ or Th4+. Single-phase garnets Y3–xCa0.5xM0.5xFe5O12 (x = 0.1–0.7) were synthesized by the citrate–nitrate combustion method. Ce was confirmed to be tetravalent by X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. X-ray diffraction and 57Fe–Mössbauer spectroscopy indicated that M4+ and Ca2+ cations are restricted to the c site, and the local environments of both the tetrahedral and the octahedral Fe3+ are systematically affected by the extent of substitution. The charge-coupled substitution has advantages in incorporating Ce/Th and in stabilizing the substituted phases compared to a single substitution strategy. Enthalpies of formation of garnets were obtained by high temperature oxide melt solution calorimetry, and the enthalpies of substitution of Ce and Th were determined. The thermodynamic analysis demonstrates that the substituted garnets are entropically rather than energetically stabilized. This suggests that such garnets maymore » form and persist in repositories at high temperature but might decompose near room temperature.« less

Authors:
; ; ; ; ; ;  [1]
  1. UCD
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Materials Science of Actinides (MSA); Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
DOE - BASIC ENERGY SCIENCES
OSTI Identifier:
1178827
Resource Type:
Journal Article
Journal Name:
Inorg. Chem.
Additional Journal Information:
Journal Volume: 54; Journal Issue: (8) ; 04, 2015
Country of Publication:
United States
Language:
ENGLISH

Citation Formats

Guo, Xiaofeng, Kukkadapu, Ravi K., Lanzirotti, Antonio, Newville, Matthew, Engelhard, Mark H., Sutton, Stephen R., Navrotsky, Alexandra, UC), and PNNL). Charge-Coupled Substituted Garnets (Y3-xCa0.5xM0.5x)Fe5O12 (M = Ce, Th): Structure and Stability as Crystalline Nuclear Waste Forms. United States: N. p., 2015. Web. doi:10.1021/acs.inorgchem.5b00444.
Guo, Xiaofeng, Kukkadapu, Ravi K., Lanzirotti, Antonio, Newville, Matthew, Engelhard, Mark H., Sutton, Stephen R., Navrotsky, Alexandra, UC), & PNNL). Charge-Coupled Substituted Garnets (Y3-xCa0.5xM0.5x)Fe5O12 (M = Ce, Th): Structure and Stability as Crystalline Nuclear Waste Forms. United States. https://doi.org/10.1021/acs.inorgchem.5b00444
Guo, Xiaofeng, Kukkadapu, Ravi K., Lanzirotti, Antonio, Newville, Matthew, Engelhard, Mark H., Sutton, Stephen R., Navrotsky, Alexandra, UC), and PNNL). 2015. "Charge-Coupled Substituted Garnets (Y3-xCa0.5xM0.5x)Fe5O12 (M = Ce, Th): Structure and Stability as Crystalline Nuclear Waste Forms". United States. https://doi.org/10.1021/acs.inorgchem.5b00444.
@article{osti_1178827,
title = {Charge-Coupled Substituted Garnets (Y3-xCa0.5xM0.5x)Fe5O12 (M = Ce, Th): Structure and Stability as Crystalline Nuclear Waste Forms},
author = {Guo, Xiaofeng and Kukkadapu, Ravi K. and Lanzirotti, Antonio and Newville, Matthew and Engelhard, Mark H. and Sutton, Stephen R. and Navrotsky, Alexandra and UC) and PNNL)},
abstractNote = {The garnet structure has been proposed as a potential crystalline nuclear waste form for accommodation of actinide elements, especially uranium (U). In this study, yttrium iron garnet (YIG) as a model garnet host was studied for the incorporation of U analogs, cerium (Ce) and thorium (Th), incorporated by a charge-coupled substitution with calcium (Ca) for yttrium (Y) in YIG, namely, 2Y3+ = Ca2+ + M4+, where M4+ = Ce4+ or Th4+. Single-phase garnets Y3–xCa0.5xM0.5xFe5O12 (x = 0.1–0.7) were synthesized by the citrate–nitrate combustion method. Ce was confirmed to be tetravalent by X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. X-ray diffraction and 57Fe–Mössbauer spectroscopy indicated that M4+ and Ca2+ cations are restricted to the c site, and the local environments of both the tetrahedral and the octahedral Fe3+ are systematically affected by the extent of substitution. The charge-coupled substitution has advantages in incorporating Ce/Th and in stabilizing the substituted phases compared to a single substitution strategy. Enthalpies of formation of garnets were obtained by high temperature oxide melt solution calorimetry, and the enthalpies of substitution of Ce and Th were determined. The thermodynamic analysis demonstrates that the substituted garnets are entropically rather than energetically stabilized. This suggests that such garnets may form and persist in repositories at high temperature but might decompose near room temperature.},
doi = {10.1021/acs.inorgchem.5b00444},
url = {https://www.osti.gov/biblio/1178827}, journal = {Inorg. Chem.},
number = (8) ; 04, 2015,
volume = 54,
place = {United States},
year = {Mon Jun 08 00:00:00 EDT 2015},
month = {Mon Jun 08 00:00:00 EDT 2015}
}

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Works referencing / citing this record:

Sample seal-and-drop device and methodology for high temperature oxide melt solution calorimetric measurements of PuO 2
journal, April 2019


Effect of calcium oxide doping on the microstructure and optical properties of YAG transparent ceramics
journal, December 2018