TY - JOUR
T1 - Thermodynamics of thorium substitution in yttrium iron garnet
T2 - Comparison of experimental and theoretical results
AU - Guo, X.
AU - Rak, Zs
AU - Tavakoli, A. H.
AU - Becker, U.
AU - Ewing, R. C.
AU - Navrotsky, A.
N1 - Publisher Copyright:
© the Partner Organisations 2014.
Copyright:
Copyright 2014 Elsevier B.V., All rights reserved.
PY - 2014/10/28
Y1 - 2014/10/28
N2 - The thermodynamic stability of Th-doped yttrium iron garnet (Y3Fe5O12, YIG) as a possible actinide-bearing material has been investigated using calorimetric measurements and first-principles electronic-structure calculations. Yttrium iron garnet with thorium substitution ranging from 0.04 to 0.07 atoms per formula unit (Y3-xThxFe5O12, x = 0.04-0.07) was synthesized using a citrate-nitrate combustion method. High-temperature oxide melt solution calorimetry was used to determine their enthalpy of formation. The thermodynamic analysis demonstrates that, although the substitution enthalpy is slightly endothermic, an entropic driving force for the substitution of Th for Y leads to a near-zero change in the Gibbs free energy. First-principles calculations within the density functional theory (DFT) indicate that the main limiting factors for Th incorporation into the YIG structure are the narrow stability domain of the host YIG and the formation of ThO2 as a secondary phase. Nevertheless, the defect formation energy calculations suggest that by carefully tuning the atomic and electronic chemical potentials, Th can be incorporated into YIG. The thermodynamic results, as a whole, support the possible use of garnet phases as nuclear waste forms; however, this will require careful consideration of the repository conditions. This journal is
AB - The thermodynamic stability of Th-doped yttrium iron garnet (Y3Fe5O12, YIG) as a possible actinide-bearing material has been investigated using calorimetric measurements and first-principles electronic-structure calculations. Yttrium iron garnet with thorium substitution ranging from 0.04 to 0.07 atoms per formula unit (Y3-xThxFe5O12, x = 0.04-0.07) was synthesized using a citrate-nitrate combustion method. High-temperature oxide melt solution calorimetry was used to determine their enthalpy of formation. The thermodynamic analysis demonstrates that, although the substitution enthalpy is slightly endothermic, an entropic driving force for the substitution of Th for Y leads to a near-zero change in the Gibbs free energy. First-principles calculations within the density functional theory (DFT) indicate that the main limiting factors for Th incorporation into the YIG structure are the narrow stability domain of the host YIG and the formation of ThO2 as a secondary phase. Nevertheless, the defect formation energy calculations suggest that by carefully tuning the atomic and electronic chemical potentials, Th can be incorporated into YIG. The thermodynamic results, as a whole, support the possible use of garnet phases as nuclear waste forms; however, this will require careful consideration of the repository conditions. This journal is
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U2 - 10.1039/c4ta03683b
DO - 10.1039/c4ta03683b
M3 - Article
AN - SCOPUS:84907789784
SN - 2050-7488
VL - 2
SP - 16945
EP - 16954
JO - Journal of Materials Chemistry A
JF - Journal of Materials Chemistry A
IS - 40
ER -