X-ray and thermal studies of mixed valent uranium molybdates

Keskar, Meera; Sali, S.K.; Dahale, N.D.; Krishnan, K.; Phatak, Rohan; Kulkarni, N.K.; Kannan, S.

doi:10.1016/j.jnucmat.2011.11.069

Cited by 8 publications

(4 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…47 Furthermore, the existing polymorphic ternary oxides such as α, β, and γ-UMo 2 O 8 might adopt varied OS compositions, similar to the case of seven polymorphic UO 3 . 48,49 As such, it is very necessary to obtain the atomic resolving chemical states as the starting point for the further understanding of U ternary oxides.…”

Section: Introductionmentioning

confidence: 99%

“…Taking UVO 5 as an example, the alternative compositions are U 5+ V 5+ O 5 and U 6+ V 4+ O 5 , and more compositions are possible if mixed valence U and V ions are considered . Furthermore, the existing polymorphic ternary oxides such as α, β, and γ-UMo 2 O 8 might adopt varied OS compositions, similar to the case of seven polymorphic UO 3 . , As such, it is very necessary to obtain the atomic resolving chemical states as the starting point for the further understanding of U ternary oxides.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Atom-Resolved Chemical States in the Multivalent U-TM-O (TM: Ti, V, Cr, Mn, Fe, Ni, Nb, Mo, W) Ternary Oxides from First-Principles

2019

J. Phys. Chem. C

View full text Add to dashboard Cite

Uranium (U) has attracted considerable fundamental and applied studies; among them, the rigorous determination of its chemical state is one of the crucial topics owing to its well-known multivalent feature associated with complicated chemical bonding. However, the related studies on solid-state U ternary or beyond ternary compounds are quite in lack. Herein, first-principles DFT + U calculations are performed to unambiguously determine the actual oxidation states of metal ions in U ternary oxides containing multivalent transition-metals (TMs: Ti, V, Cr, Mn, Fe, Ni, Nb, Mo, W). For the first time, the actual oxidation states of U and TM in the ternary oxides are obtained in a quantitative and atom-resolved manner, thereby providing their nominal compositions. The results disclose the variations of U oxidation states with TM's properties, chemical surrounding, local structure, and oxygen vacancy. In terms of charge transfer, electronic structure, orbital energy level, and oxygen vacancy effect, I conclude that the oxidation state is the competitive consequence of those electronic and structural factors and that electron-structure-related factors play more important roles. Because of the increasing orbital expansion from 3d to 4d and 5d TMs, the latter TMs (Nb, Mo, W) have the greater tendency to form high oxidation states and suppress the formation of high oxidation states of U. On the contrary, 3d TMs, especially Cr, Mn, Fe, and Ni, tend to adopt low oxidation states, thereby promoting the emergence of high oxidation states of U.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Atom-Resolved Chemical States in the Multivalent U-TM-O (TM: Ti, V, Cr, Mn, Fe, Ni, Nb, Mo, W) Ternary Oxides from First-Principles

2019

J. Phys. Chem. C

View full text Add to dashboard Cite

show abstract

“…Sources of reactants/products along with their purities and measurement techniques are given in Table 1. HTXRD data for ThW 2 O 8 and UWO 6 were collected on a STOE high-temperature X-ray diffractometer using HDK-2.4 Buhler high-temperature attachment in 10 -5 mbar vacuum from 298 to 1273 K. Instrumental details of HTXRD are discussed elsewhere [15]. Uncertainty in the temperature measurements is ±2 K. Before collecting high-temperature XRD data, the thermal stability of both the compounds was checked by recording TG and DTA simultaneously.…”

Section: Methodsmentioning

confidence: 99%

“…Suleimanov et al [12] calculated Gibbs free energy of formation from the measured heat capacity and enthalpy values of UO 2 MoO 4 . Extensive study has been carried out on thermophysical and thermochemical properties of ternary thorium and uranium molybdates using various techniques from our laboratory [13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Studies on thermophysical properties of ThW2O8 and UWO6

Keskar

Krishnan

Phatak

et al. 2016

J Therm Anal Calorim

Self Cite

View full text Add to dashboard Cite

Thermal stability and expansion behavior of ThW 2 O 8 and UWO 6 were studied using thermogravimetry and high-temperature X-ray diffraction techniques. ThW 2-O 8 and UWO 6 showed positive thermal expansion in vacuum from ambient to 1273 and 1073 K, respectively. Heat capacity for ThW 2 O 8 (s) and UWO 6 (s) was measured in argon atmosphere using heat flux-type differential scanning calorimeter, and thermodynamic functions of these compounds have been computed from the measured heat capacity data. The structural study of UWO 6 was also carried out from powder X-ray diffraction data using Rietveld profile method.

show abstract

Insights into Structural Diversity and Morphotropic Evolution in A₄Th(WO₄)₄ (A=Li, Na, K, Rb and Cs) Family

Yu,

Xiao,

Eichel

et al. 2024

Chemistry A European J

View full text Add to dashboard Cite

A series of four new thorium tungstates, A4Th(WO4)4 (A = Li, K, Rb, Cs), were synthesized using high‐temperature solid‐state method. Structural studies of the materials reveal distinct structural changes with underlying similarities influenced by the nature of A‐site cations. Li4Th(WO4)4 exhibits a two‐dimensional corrugated sheet structure stabilized by Li+ cations, crystallizing in P space group. K4Th(WO4)4 crystallizes in I41/a space group and exhibits a three‐dimensional framework consisting of ThO8 antiprisms and WO4 tetrahedra. Rb4Th(WO4)4 forms in C2/c space group, showcasing a framework with two‐dimensional sheet structure. Cs4Th(WO4)4 is isostructural to Rb4Th(WO4)4 but displays increased interlayer spacing due to the larger ionic radius of Cs. Raman spectroscopy confirms the structural data, revealing distinct vibrational modes that correlate with tungsten coordination changes from WO6 in Li4Th(WO4)4 to WO4 in the Cs4Th(WO4)4. This study demonstrates how variation of alkali metals affects the structural properties of thorium tungstates series, showing a morphotropic evolution as a factor of the ionic radii of the alkali metals.

show abstract

X-ray and thermal studies of mixed valent uranium molybdates

Cited by 8 publications

References 24 publications

Atom-Resolved Chemical States in the Multivalent U-TM-O (TM: Ti, V, Cr, Mn, Fe, Ni, Nb, Mo, W) Ternary Oxides from First-Principles

Atom-Resolved Chemical States in the Multivalent U-TM-O (TM: Ti, V, Cr, Mn, Fe, Ni, Nb, Mo, W) Ternary Oxides from First-Principles

Studies on thermophysical properties of ThW2O8 and UWO6

Insights into Structural Diversity and Morphotropic Evolution in A₄Th(WO₄)₄ (A=Li, Na, K, Rb and Cs) Family

Contact Info

Product

Resources

About

X-ray and thermal studies of mixed valent uranium molybdates

Cited by 8 publications

References 24 publications

Atom-Resolved Chemical States in the Multivalent U-TM-O (TM: Ti, V, Cr, Mn, Fe, Ni, Nb, Mo, W) Ternary Oxides from First-Principles

Atom-Resolved Chemical States in the Multivalent U-TM-O (TM: Ti, V, Cr, Mn, Fe, Ni, Nb, Mo, W) Ternary Oxides from First-Principles

Studies on thermophysical properties of ThW2O8 and UWO6

Insights into Structural Diversity and Morphotropic Evolution in A4Th(WO4)4 (A=Li, Na, K, Rb and Cs) Family

Contact Info

Product

Resources

About

Insights into Structural Diversity and Morphotropic Evolution in A₄Th(WO₄)₄ (A=Li, Na, K, Rb and Cs) Family