THE CRYSTAL CHEMISTRY, STRUCTURE AND PROPERTIES OF A SYNTHETIC CARNOTITE-TYPE COMPOUND, Ba2[(UO2)2Ti2O8]

Wallwork, Kia S.; James, M. R.; Carter, Melody L.

doi:10.2113/gscanmin.44.2.433

Cited by 10 publications

(19 citation statements)

References 29 publications

(33 reference statements)

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“…Even though these samples were somewhat porous (B80% theoretical density), these values are very comparable with those obtained previously for dense pyrochlore-rich ceramics produced by hot isostatic pressing (Ca: 0.02-0.04 g/L; Ti: 1-5 Â 10 À6 g/L; U: 2À5 Â 10 À5 g/L) 25 showing the current samples to be quite resistant to water leaching. Further, the normalized amount of uranium leached over 7 days is comparable with the value measured for the carnotite-type compound Ba 2 [(UO 2 ) 2 Ti 2 O 8 ] (1.15 Â 10 À5 g/L), 54 and orders of magnitude better than that for synthetic brannerite UTi 2 O 6 (U: 0.3 g/L). 55…”

Section: Resultssupporting

confidence: 76%

Section: Resultsmentioning

confidence: 99%

“…BVS have been used by a number of researchers along with structure refinements to quantify the uranium oxidation states at specific crystallographic sites within synthetic compounds and minerals, including those containing mixed-valence uranium. [46][47][48][49][50][51][52][53][54] For example, BVS calculations were carried out We have shown previously that brannerite phases U 1Àx Ca x Ti 2 O 6 prepared at 14001C can accommodate a reasonable range of solid solution due to calcium doping at the A site. 52 When prepared in air, a relatively small solid solution range was evident (0.21rxr0.28), while a larger range was possible when sintered under argon (0rxr0.28).…”

Section: Resultsmentioning

confidence: 99%

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Crystal Chemistry and Structures of (Ca,U) Titanate Pyrochlores

James¹,

Carter²,

Zhang³

et al. 2010

Journal of the American Ceramic Society

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Analysis of multiphase (Ca,U) titanate pyrochlore samples produced under argon or in air, using laboratory X‐ray powder diffraction (XRD) and electron microscopy revealed discrete pyrochlore phase compositions, together with either perovskite or rutile impurities. Investigations of these samples using diffuse reflectance and X‐ray photoelectron spectroscopies revealed mixed U4+/U5+ oxidation states for argon‐annealed samples and U5+/U6+ oxidation states for air‐annealed samples. Single‐phase (Ca1.25U4+0.25U5+0.50)Ti2O7 (argon) and (Ca1.40U5+0.60)(Ti1.90U6+0.10)O7 (air) compositions were synthesized and characterized using a combination of synchrotron X‐ray and neutron powder diffraction. Severe intensity reduction of hkl odd XRD peaks from the sample produced in air was found to be the result of U6+ sharing the Ti site. The refined crystal structures for both single‐phase samples were found to be consistent with the compositions and mixed oxidation states observed by the above spectroscopic measurements. Although the normalized uranium leach rate of the argon‐annealed sample was found to be approximately twice that of the air‐annealed sample, in 7‐day Product Consistency Test the durability of both compounds with respect to leaching by water was found to be excellent. Ca releases were in the range of 0.01–0.03 g/L and U releases were <3 × 10−5 g/L.

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Section: Resultssupporting

confidence: 76%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Crystal Chemistry and Structures of (Ca,U) Titanate Pyrochlores

James¹,

Carter²,

Zhang³

et al. 2010

Journal of the American Ceramic Society

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“…The reflection data were recorded in scan mode at 2-90 degree of 2θ with an interval of 0.02 and rate of 10. The resulting diffractogram was then analyzed by Le Bail method of Rietica program (5-50 degree of 2θ) being usually applied to metal oxides [e.g., [8][9][10], which was run within 30 cycles.…”

Section: Powder X-ray Diffractionmentioning

confidence: 99%

Synthesis and Structural Analysis of Powder Complex of Tris(bipyridine)cobalt(II) Trifluoromethanesulfonate Octahydrate

2018

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The powder complex of tris(bipyridine)cobalt(II) trifluoromethanesulfonate octahydrate has been synthesized by direct interaction of the corresponding aqueous solutions (and drops of ethanol) of cobalt(II) nitrate, bipyridine, and potassium triflate. The yellow-orange powder produced was filtered off and allowed to dry on an aeration for characterization. AAS measurement showed the content of metal to be 6.06%, corresponding to the theoretical value of 6.06% in [Co(bipy)3](CF3SO3)2•8H2O. The analysis of conductance producing the charge ratio of cation to anion to be 2:1, confirms the formula. The magnetic moment, µeff, of this complex which was to be 4.5-4.9 BM, indicates that the complex is paramagnetic corresponding to the three unpaired electrons with a significantly orbital contribution. UV-Vis spectrum of the complex reveals the first band observed at about 11100 cm -1 , which is associated with the spinallowed transition, 4 T1g → 4 T2g. A distinct shoulder at only about 16100 cm -1 should be associated with the spinforbidden transition of 4 T1g → 2 T2g, 2 T2g (G). The expected second and third bands which are associated with spinallowed transitions of 4 T1g → 4 T1g(P) and 4 T1g → 4 A2g at higher energy were not well resolved. The infrared spectrum shows absorptions of the functional group of ligand which is influenced by the metal-ligand interaction in this complex. The powder XRD of this complex was refined using Le Bail method of Rietica program and found to be fit as monoclinic symmetry with a space group of C2/c. (II) nitrat, bipiridin, dan kalium triflat. Serbuk kuningorange yang terbentuk disaring dan dikeringkan untuk keperluan karakterisasi. Pengukuran AAS yang menunjukkan kandungan logam 6,06%, sesuai dengan nilai teoretis 6,06% pada [Co(bipy)3](CF3SO3)2•8H2O. Analisis daya hantar listrik ekivalen menghasilkan rasio muatan kation/anion 2:1, menegaskan formula tersebut. Momen magnetik, µeff, sebesar 4.5-4.9 BM, menunjukkan kompleks bersifat paramagnetik yang sesuai dengan tiga elektron nir-pasangan dengan kontribusi orbital yang kuat. Spektrum UV-Vis kompleks mengungkap pita pertama pada 11100 cm -1 , yang diasosiasikan dengan transisi spin-terijin, 4 T1g → 4 T2g. Suatu pundak yang sangat jelas pada 16100 cm -1 menunjuk pada transisi spin-terlarang, 4 T1g → 2 T2g, 2 T2g (G). Pita kedua dan ketiga yang diharapkan menunjuk pada transisi spinterijin 4 T1g → 4 T1g(P) dan 4 T1g → 4 A2g pada energi yang lebih tinggi tidak muncul secara jelas. Spektrum infra merah menunjukkan serapan gugus-fungsi khas bagi ligan yang dipengaruhi oleh interaksi logam-ligan. Difraksi sinar-X serbuk kompleks ini yang dianalisis menurut metode Le Bail dalam program Rietica menghasilkan simetri kristal monoklin dengan grup ruang C2/c. ABSTRAK Serbuk kompleks tris(bipiridine)kobalt(II) trifluorometanasulfonat telah berhasil disintesis melalui interaksi langsung larutan air dengan beberapa tetes etanol dari kobalt

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“…It is not surprising since the preparation of a single crystal suitable for refining the structural data of particular complex is sometimes quite complicated and even unsuccessful. Rietica is one of known programs of Le Bail to refine the lattice parameters for various metal oxides [2][3][4] which are found to be fit, and it seems also applicable for other powders of complexes. The first complex refined by Le Bail program was initially reported in 1999 [5] for octahedral [Co(NH3)5CO3](NO3)•H2O complex which was found very good result with the figures of merit to be RB = 0.053, Rp = 0.100, Rwp = 0.119.…”

Section: ■ Introductionmentioning

confidence: 99%

Preparation and Powder XRD Analysis of Tris(2,2’-bipyridine)nickel(II) Trifluoroacetate

2020

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The complex containing Ni(II)-2,2’-bipyridin (bipy)-trifluoroacetate (TFA) was prepared by direct interaction of the corresponding precursors in an aqueous solution. AAS measurement for metal content, TGA-DTA analysis and electrical conductance suggest the ionic complex of [Ni(bipy)3](CF3COO)2·6H2O. The magnetic moment of 3.13–3.17 BM indicates the paramagnetism corresponding to two unpaired electrons which is clearly higher than that of the spin only value (2.87 BM), and commonly observed due to the spin-orbit coupling in Ni(II). UV-Vis spectral property revealed the first two main ligand field bands centered at about 14200 and 18650 cm–1, which are attributed to the spin-allowed transition, 3A2g→3T2g and 3A2g→3T1g(F), respectively. The expected third band at higher energy seems to appear as a shoulder at 26500 cm–1 (378 nm), as it is masked by a strong intensity of charge transfer band centered at 31050 cm–1. The infrared spectrum exhibits mode of vibrations of the functional groups of ligand and TFA. The powder diffractogram was refined by Le Bail method and found fit as monoclinic system of space group of P21/M, with figures of merit: Rp = 3.62, Rwp = 5.76, Rexp = 3.48, goodness of fitting (GOF) 2.745 and the derived Bragg R-Factor = 0.05.

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THE CRYSTAL CHEMISTRY, STRUCTURE AND PROPERTIES OF A SYNTHETIC CARNOTITE-TYPE COMPOUND, Ba2[(UO2)2Ti2O8]

Cited by 10 publications

References 29 publications

Crystal Chemistry and Structures of (Ca,U) Titanate Pyrochlores

Crystal Chemistry and Structures of (Ca,U) Titanate Pyrochlores

Synthesis and Structural Analysis of Powder Complex of Tris(bipyridine)cobalt(II) Trifluoromethanesulfonate Octahydrate

Preparation and Powder XRD Analysis of Tris(2,2’-bipyridine)nickel(II) Trifluoroacetate

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