Oxygen and phosphorus coordination around iron in crystalline ferric ferrous pyrophosphate and iron-phosphate glasses with UO2 or Na2O

1999 ◽  
Vol 14 (6) ◽  
pp. 2628-2639 ◽  
Author(s):  
C. H. Booth ◽  
P. G. Allen ◽  
J. J. Bucher ◽  
N. M. Edelstein ◽  
D. K. Shuh ◽  
...  
Keyword(s):  
Fine Structure ◽  
Iron Phosphate ◽  
Phosphate Glasses ◽  
Base Glass ◽  
Related Material ◽  
X Ray ◽  
Absorption Fine ◽  
Iron Substitution ◽  
Iron Phosphate Glasses ◽  
X Ray Absorption

Fe K-edge x-ray absorption fine-structure (XAFS) measurements were performed on glass samples of (Fe3O4)0.3(P2O5)0.7 with various amounts of Na2O or UO2. Near-edge and extended XAFS regions are studied and comparisons are made to several reference compounds. We find that iron in the base glass is ∼25% divalent and that the Fe2+ coordination is predominantly octahedral, while Fe3+ sites are roughly split between tetrahedral and octahedral coordinations. Also, we measure roughly one Fe–O–P link per iron. Substitution of Na2O or UO2 up to 15 mol% primarily affects the first Fe–O shell. The results are compared to data from the related material Fe3(P2O7)2.

Local environment of iron and uranium ions in vitrified iron phosphate glasses studied by Fe K and U LIII-edge x-ray absorption fine structure spectroscopy

2000 ◽  
Vol 15 (9) ◽  
pp. 1972-1984 ◽  
Author(s):  
M. Karabulut ◽  
G. K. Marasinghe ◽  
C. S. Ray ◽  
D. E. Day ◽  
G. D. Waddill ◽  
...  
Keyword(s):  
Fine Structure ◽  
Average Distance ◽  
Iron Phosphate ◽  
Phosphate Glasses ◽  
Edge Structure ◽  
X Ray ◽  
Absorption Fine ◽  
Uranium Ions ◽  
Iron Phosphate Glasses ◽  
X Ray Absorption

The local structure of iron and uranium ions in a series of iron phosphate glasses with the general composition (40 – x)Fe2O3–xUO2–60P2O5 and (1–x–y)(40Fe2O3–60P2O5)– xUO2–y(Na2O or CaO) was investigated using Fe K-edge and U LIII-edge x-ray absorption fine structure spectroscopy. Replacing Fe2O3 by UO2 in the glass caused more distortion in the coordination environment of Fe(III) ions. Extended x-ray absorption fine structure fits revealed that the Fe–P bonds observed in the base glass also existed in all the waste-loaded glasses. X-ray absorption near-edge structure showed that the uranium ions were predominantly present as U(IV) in the glasses. Uranium ions were coordinated to approximately 8 ± 1 oxygen atoms and 2.5 ± 0.6 phosphorus atoms at an average distance of 2.47 ± 0.02 and 3.8 ± 0.02 Å, respectively. There were no Fe–U or U–Fe neighbors observed, indicating that uranium ions occupied voids in the glass away from the PO4 units. These conclusions were supported by Mössbauer, x-ray photoelectron, and Raman spectroscopic data.

An X-ray absorption spectroscopy study of the local environment of iron in degradable iron–phosphate glasses

2008 ◽  
Vol 354 (52-54) ◽  
pp. 5542-5546 ◽  
Author(s):  
Dong Qiu ◽  
Robert M. Moss ◽  
Dave M. Pickup ◽  
Ifty Ahmed ◽  
Jonathan C. Knowles ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Local Environment ◽  
Iron Phosphate ◽  
Phosphate Glasses ◽  
Spectroscopy Study ◽  
X Ray ◽  
Iron Phosphate Glasses ◽  
X Ray Absorption

The Effects of Uranium on the Structure of Iron Phosphate Glasses

1999 ◽  
Vol 556 ◽  
Author(s):  
Yaspal Badyal ◽  
Mevlut Karabulut ◽  
Kanishka Marasinghe ◽  
Marie-Louise Saboungi ◽  
Dean Haeffner ◽  
...  
Keyword(s):  
Glass Structure ◽  
Iron Phosphate ◽  
High Energy ◽  
Structural Features ◽  
Real Space ◽  
Phosphate Glasses ◽  
Base Glass ◽  
Pair Correlations ◽  
X Ray ◽  
Iron Phosphate Glasses

AbstractBecause of their high chemical durability and waste loading capacity, iron phosphate glasses are a natural candidate for a nuclear waste disposal medium. We have studied the effects of uranium on the structure of iron phosphate glasses with both neutron and high-energy x-raydiffraction. The results of neutron scattering, which is mostly sensitive to pair correlations involving light atoms i.e. O-O, Fe-O and P-O, indicate the main structural features of the base glass are largely unaffected by the addition of UO2. The nearest-neighborbour P-O, Fe-O and O- O peaks remain at the same position in real space and their intensities scale approximately with concentration. These findings are consistent with earlier results using Raman scattering and EXAFS on the Fe-K edge, where in both cases the spectra remain similar to the base glass. The results of high-energy x-ray scattering, which is sensitive to correlations involving the heavier atoms and thus complements the neutron measurements, are also consistent with the overall picture of uranium occupying interstitial sites in the relatively undisturbed base glass structure. Combining the neutron and x-ray data for a 10 mol% UO2 glass suggests the intriguing possibility of a U6+ uranyl ion configuration although further work is needed to establish the precise local structure and valence state of uranium in these glasses.

Xanes (X-ray absorption near edge structure) of V in vanadium-iron phosphate glasses

1982 ◽  
Vol 42 (8) ◽  
pp. 547-551 ◽  
Author(s):  
A. Bianconi ◽  
A. Giovannelli ◽  
I. Dovoli ◽  
S. Stizza ◽  
L. Palladino ◽  
...  
Keyword(s):  
Iron Phosphate ◽  
Phosphate Glasses ◽  
Edge Structure ◽  
X Ray ◽  
Vanadium Iron ◽  
Iron Phosphate Glasses ◽  
X Ray Absorption

scholarly journals An extended x-ray absorption fine structure study of rare-earth phosphate glasses near the metaphosphate composition

1999 ◽  
Vol 14 (12) ◽  
pp. 4706-4714 ◽  
Author(s):  
R. Anderson ◽  
T. Brennan ◽  
J. M. Cole ◽  
G. Mountjoy ◽  
D. M. Pickup ◽  
...  
Keyword(s):  
Fine Structure ◽  
Rare Earth ◽  
Variable Temperature ◽  
Structure Study ◽  
Phosphate Glasses ◽  
Rare Earth Ions ◽  
Glassy Matrix ◽  
X Ray ◽  
Absorption Fine ◽  
X Ray Absorption

A variable-temperature (79, 145, and 293 K) extended x-ray absorption fine structure study, using rare-earth LIII absorption edges, is reported for phosphate glasses doped with rare-earth elements (R, where R = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er) with compositions close to metaphosphate, R(PO3)3. The results yield nearest-neighbor R–O distances that demonstrate the lanthanide contraction in a glassy matrix and an R–O coordination intermediate between 6 and 7 for rare-earth ions with smaller atomic number (Z) and 6 for rare-earth ions with largerZ. Thermal parameters show no significant changes in R–O distances or coordination numbers between 293 and 79 K. There is evidence of an R–P correlation between 3.3 and 3.6 Å and the beginning of a second R–O correlation at approximately 4 Å. No R–R correlations up to a distance of approximately 4 Å were observed.

Sign in / Sign up

Export Citation Format

Share Document