Thermodynamics and phase relationships of the ternary lanthanum-uranium-oxygen system

Stadlbauer, E. A.; Wichmann, U.; Lott, U.; Keller, C.

doi:10.1016/0022-4596(74)90043-7

Cited by 61 publications

(24 citation statements)

References 13 publications

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“…We consider three different oxygen to metal ratios, namely "reduced" (fully charge-compensated with oxygen vacancies), "stoichiometric" (fully chargecompensated with U 5+ ions), and "intermediate" (charge-compensated by both oxygen vacancies and U 5+ ions). Specifically, the "reduced regime" considers U 4 After enumerating the different possible configurations at the different oxygen concentrations we use ionic pair potential models [44] to screen out configurations with large energies, and employ density functional theory (DFT) based methods to determine energies of the lowest-energy structures. The DFT energies were obtained within the formalism of the projector augmented wave (PAW) method [46] and the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) [48] as implemented in the Vienna ab initio Simulation Package (VASP) [50].…”

Section: Methodsmentioning

confidence: 99%

A combined calorimetric and computational study of the energetics of rare earth substituted UO2 systems

et al. 2015

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The energetics of rare earth substituted UO 2 solid solutions (U 1-x Ln x O 2-0.5x+y , where Ln = La, Y, and Nd) are investigated employing a combination of calorimetric measurements and density functional theory based computations. Calculated and measured formation enthalpies agree within 10 kJ/mol for stoichiometric oxygen/metal compositions. To better understand the factors governing the stability and defect binding in rare earth substituted urania solid solutions, systematic trends in the energetics are investigated based on the present results and previous computational and experimental thermochemical studies of rare earth substituted fluorite oxides (A 1-x Ln x O 2-0.5x , where A = Hf, Zr, Ce, and Th). A consistent trend towards increased energetic stability with larger size mismatch between the smaller host tetravalent cation and the larger rare earth trivalent cation is found for both actinide and non-actinide fluorite oxide systems where aliovalent substitution of Ln cations is compensated by oxygen vacancies. However, the large exothermic oxidation enthalpy in the UO 2 based systems favors oxygen rich compositions where charge compensation occurs through the formation of uranium cations with higher oxidation states.

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Section: Methodsmentioning

confidence: 99%

A combined calorimetric and computational study of the energetics of rare earth substituted UO2 systems

et al. 2015

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“…The extent of solubility of lanthanum oxide in UO 2 lattice depends on factors such as temperature, O/M, ambient conditions during heat treatment (oxidizing reducing or vacuum) etc. [6][7][8][9][10][11][12]. The results are consolidated and reported in a review article [6].…”

Section: Introductionmentioning

confidence: 98%

Solubility studies and thermal expansion coefficient of uranium–lanthanum mixed oxide system

Krishnan

Panneerselvam

Antony

et al. 2010

Journal of Nuclear Materials

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“…The lanthanide elements have high fission yields and are known to form solid solutions with UO 2 over a wide range of compositions. As the yield of fission product lanthanum in the fission of uranium is relatively high, uranium–lanthanum‐mixed oxides have been studied by various authors . Lanthanum is dissolved in UO 2 to form a solid solution (U, La)O 2± x with a fluorite structure, where the La 3+ ions substitute on the uranium sublattice and can create an oxygen vacancy environment that is similar to the hypostoichiometric UO 2− x .…”

Section: Introductionmentioning

confidence: 99%

“…As the yield of fission product lanthanum in the fission of uranium is relatively high, uranium-lanthanum-mixed oxides have been studied by various authors. [1][2][3][4][5][6][7][8][9] Lanthanum is dissolved in UO 2 to form a solid solution (U, La)O 2AEx with a fluorite structure, where the La 3+ ions substitute on the uranium sublattice and can create an oxygen vacancy environment that is similar to the hypostoichiometric UO 2Àx . The crystal chemistry of this solid solution, could be described as (U 4+ (1ÀxÀy) ,U 5+ (x) ,La 3+ (y) )(O (2+x/2Ày/2) ) with the special cases ( Nevertheless, the effect of lanthanides dopants on the oxidation of UO 2 still presents open question calling for further research.…”

Section: Introductionmentioning

confidence: 99%

Raman and X‐ray Studies of Uranium–Lanthanum‐Mixed Oxides Before and After Air Oxidation

et al. 2015

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UO 2 samples doped with 6, 11, 22 mol% lanthanum were examined before and after air oxidation. To verify the formation of uranium-lanthanum-mixed oxide solid solutions, powder X-ray diffraction (XRD) analyses of the crystalline phases in the materials were carried out. The presence of oxygen vacancies in the La-doped UO 2 samples was identified by Raman spectrometry. It was evidenced by changes induced in the Raman spectra by air oxidation. This latter was carried out either by increasing the Raman laser power or by thermally treating the samples at 500 K for 370 h. In addition, oxidation behavior differences of pure and La-doped UO 2 samples were reported by comparing XRD and Raman results of the samples before and after air oxidation. It was shown that the concentration of the M 4 O 9 (M: U, La) phase increased with increasing content of La, whereas inhibition for the formation of M 3 O 8 phase was observed.

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Thermodynamics and phase relationships of the ternary lanthanum-uranium-oxygen system

Cited by 61 publications

References 13 publications

A combined calorimetric and computational study of the energetics of rare earth substituted UO2 systems

A combined calorimetric and computational study of the energetics of rare earth substituted UO2 systems

Solubility studies and thermal expansion coefficient of uranium–lanthanum mixed oxide system

Raman and X‐ray Studies of Uranium–Lanthanum‐Mixed Oxides Before and After Air Oxidation

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