Structural Characterisations of Rare Earth-Rich Glasses for Nuclear Waste Immobilisation

2003 ◽  
Vol 807 ◽  
Author(s):  
I. Bardez ◽  
D. Caurant ◽  
F. Ribot ◽  
P. Loiseau ◽  
J. L. Dussossoy ◽  
...  
Keyword(s):  
Rare Earth ◽  
Nuclear Waste ◽  
Glass Composition ◽  
Optical Absorption Spectroscopy ◽  
X Ray ◽  
Liquid Wastes ◽  
X Ray Absorption ◽  
Glassy Matrices ◽  
Characterisation Methods ◽  
The Rare Earth

ABSTRACTNew glassy matrices, able to incorporate new highly concentrated radioactive liquid wastes (HLW), are being studied. Investigations were performed on rare earth-rich glasses, known as very durable matrices. The selected basic glass composition was (wt. %): 51.0 SiO2 – 8.5 B2O3–12.2 Na2O – 4.3 Al2O3 – 4.8 CaO – 3.2 ZrO2 – 16.0 Nd2O3. To determine both the environment around the rare earth in this glass and its evolution according to its concentration (1.3 – 30 wt. % Nd2O3), EXAFS (Extended X-Ray Absorption Fine Structure) spectroscopy at the LIII-edge of neodymium and optical absorption spectroscopy were used. By coupling these two characterisation methods, several hypotheses are proposed about the nature of the rare earth neighbouring in the glass.

scholarly journals Electronic Structure of the Rare-Earth Nitrides

2021 ◽  
Author(s):  
◽  
A. R. H. Preston
Keyword(s):  
Electronic Structure ◽  
Rare Earth ◽  
Band Structure ◽  
Electronic Band Structure ◽  
Electronic Band ◽  
X Ray ◽  
Rare Earth Nitrides ◽  
Wide Range ◽  
X Ray Absorption ◽  
The Rare Earth

<p>The rare-earth nitrides (ReNs) are a class of novel materials with potential for use in spintronics applications. Theoretical studies indicate that among the ReNs there could be half-metals, semimetals and semiconductors, all exhibiting strong magnetic ordering. This is because of the complex interaction between the partially filled rare-earth 4f orbital and the nitrogen 2p valence and rare-earth 5d conduction bands. This thesis uses experimental and theoretical techniques to probe the ReN electronic structure. Thin films of SmN, EuN, GdN, DyN, LuN and HfN have been produced for study. Basic characterization shows that the films are of a high quality. The result of electrical transport, magnetometry, and optical and x-ray spectroscopy are interpreted to provide information on the electronic structure. SmN, GdN, DyN are found to be semiconductors in their ferromagnetic ground state while HfN is a metal. Results are compared with density functional theory (DFT) based calculations. The free parameters resulting from use of the local spin density approximation with Hubbard-U corrections as the exchange-correlation functional are adjusted to reach good agreement with x-ray absorption and emission spectroscopy at the nitrogen K-edge. Resonant x-ray emission is used to experimentally measure valence band dispersion of GdN. No evidence of the rare-earth 4f levels is found in any of the K-edge spectroscopy, which is consistent with the result of M-edge x-ray absorption which show that the 4f wave function of the rare-earths in the ReNs are very similar to those of rare-earth metal. An auxillary resonant x-ray emission study of ZnO is used to map the dispersion of the electronic band structure across a wide range of the Brillouin zone. The data, and calculations based on GW corrections to DFT, together provide a detailed picture of the bulk electronic band structure.</p>

scholarly journals X-Ray Absorption Spectroscopy of the Rare Earth Orthophosphates

1993 ◽  
Vol 307 ◽  
Author(s):  
D. K. Shuh ◽  
L. J. Terminello ◽  
L. A. Boatner ◽  
M. M. Abraham
Keyword(s):  
Rare Earth ◽  
Absorption Spectroscopy ◽  
Total Yield ◽  
Electronic Transitions ◽  
X Ray ◽  
Trivalent State ◽  
Theoretical Investigations ◽  
Radiation Laboratory ◽  
X Ray Absorption ◽  
The Rare Earth

ABSTRACTX-ray Absorption Spectroscopy (XAS) of the Rare Earth (RE) 3d levels yields sharp peaks near the edges as a result of strong, quasi-atomic 3d104fn→3d94fn+1 transitions and these transitions exhibit a wealth of spectroscopic features. The XAS measurements of single crystal REPO4 (RE = La, Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy, Er) at the 3d edge were performed in the total yield mode at beam line 8–2 at the Stanford Synchrotron Radiation Laboratory (SSRL). The XAS spectra of the RE ions in the orthophosphate matrix generally resemble the XAS of the corresponding RE metal. This is not unexpected and emphasizes the major contribution of the trivalent state to the electronic transitions at the RE 3d edges. These spectra unequivocally identify the transitions originating from well-characterized RE cores and correlate well with previous theoretical investigations.

scholarly journals Electronic Structure of the Rare-Earth Nitrides

2021 ◽  
Author(s):  
◽  
A. R. H. Preston
Keyword(s):  
Electronic Structure ◽  
Rare Earth ◽  
Band Structure ◽  
Electronic Band Structure ◽  
Electronic Band ◽  
X Ray ◽  
Rare Earth Nitrides ◽  
Wide Range ◽  
X Ray Absorption ◽  
The Rare Earth

<p>The rare-earth nitrides (ReNs) are a class of novel materials with potential for use in spintronics applications. Theoretical studies indicate that among the ReNs there could be half-metals, semimetals and semiconductors, all exhibiting strong magnetic ordering. This is because of the complex interaction between the partially filled rare-earth 4f orbital and the nitrogen 2p valence and rare-earth 5d conduction bands. This thesis uses experimental and theoretical techniques to probe the ReN electronic structure. Thin films of SmN, EuN, GdN, DyN, LuN and HfN have been produced for study. Basic characterization shows that the films are of a high quality. The result of electrical transport, magnetometry, and optical and x-ray spectroscopy are interpreted to provide information on the electronic structure. SmN, GdN, DyN are found to be semiconductors in their ferromagnetic ground state while HfN is a metal. Results are compared with density functional theory (DFT) based calculations. The free parameters resulting from use of the local spin density approximation with Hubbard-U corrections as the exchange-correlation functional are adjusted to reach good agreement with x-ray absorption and emission spectroscopy at the nitrogen K-edge. Resonant x-ray emission is used to experimentally measure valence band dispersion of GdN. No evidence of the rare-earth 4f levels is found in any of the K-edge spectroscopy, which is consistent with the result of M-edge x-ray absorption which show that the 4f wave function of the rare-earths in the ReNs are very similar to those of rare-earth metal. An auxillary resonant x-ray emission study of ZnO is used to map the dispersion of the electronic band structure across a wide range of the Brillouin zone. The data, and calculations based on GW corrections to DFT, together provide a detailed picture of the bulk electronic band structure.</p>

scholarly journals High-pressure synthesis of REB5O8(OH)2 (RE = Ho, Er, Tm)

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Michael Zoller ◽  
Hubert Huppertz
Keyword(s):  
High Pressure ◽  
Rare Earth ◽  
Ir Spectroscopy ◽  
Earth Metal ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structure Solution ◽  
Pressure Synthesis ◽  
The Rare Earth

AbstractThe rare earth oxoborates REB5O8(OH)2 (RE = Ho, Er, Tm) were synthesized in a Walker-type multianvil apparatus at a pressure of 2.5 GPa and a temperature of 673 K. Single-crystal X-ray diffraction data provided the basis for the structure solution and refinement. The compounds crystallize in the monoclinic space group C2 (no. 5) and are composed of a layer-like structure containing dreier and sechser rings of corner sharing [BO4]5− tetrahedra. The rare earth metal cations are coordinated between two adjacent sechser rings. Further characterization was performed utilizing IR spectroscopy.

scholarly journals Determination of the relative concentrations of rare earth ions by x-ray absorption spectroscopy: Application to terbium mixed oxides

1986 ◽  
Vol 47 (4) ◽  
pp. 413-416 ◽  
Author(s):  
G. van der Laan ◽  
J.C. fuggle ◽  
M.P. van Dijk ◽  
A.J. Burggraaf ◽  
J.-M. Esteva ◽  
...  
Keyword(s):  
Rare Earth ◽  
Absorption Spectroscopy ◽  
Mixed Oxides ◽  
Rare Earth Ions ◽  
X Ray ◽  
X Ray Absorption

Single-crystal Data of Ternary Germanides RE2Nb3Ge4 (RE = Sc, Y, Gd–Er, Lu) and Sc2Ta3Ge4 with Ordered Sm5Ge4-type Structure

2013 ◽  
Vol 68 (5-6) ◽  
pp. 625-634 ◽  
Author(s):  
Bastian Reker ◽  
Samir F. Matar ◽  
Ute Ch. Rodewald ◽  
Rolf-Dieter Hoffmann ◽  
Rainer Pöttgen
Keyword(s):  
Rare Earth ◽  
Single Crystal ◽  
Coordination Number ◽  
Electronic Structure Calculations ◽  
Crystal Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Arc Melting ◽  
Structure Calculations ◽  
The Rare Earth

Small single crystals of the Sm5Ge4-type (space group Pnma) germanides RE2Nb3Ge4 (RE = Sc, Y, Gd-Er, Lu) and Sc2Ta3Ge4 were synthesized by arc-melting of the respective elements. The samples were characterized by powder and single-crystal X-ray diffraction. In all structures, except for Sc2.04Nb2.96Ge4 and Sc2.19Ta2.81Ge4, the rare earth and niobium atoms show full ordering on the three crystallographically independent samarium sites of the Sm5Ge4 type. Two sites with coordination number 6 are occupied by niobium, while the slightly larger site with coordination number 7 is filled with the rare earth element. Small homogeneity ranges with RE=Nb and RE=Ta mixing can be expected for all compounds. The ordered substitution of two rare earth sites by niobium or tantalum has drastic effects on the coordination number and chemical bonding. This was studied for the pair Y5Ge4/Y2Nb3Ge4. Electronic structure calculations show larger charge transfer from yttrium to germanium for Y5Ge4, contrary to Y2Nb3Ge4 which shows stronger covalent bonding due to the presence of Nb replacing Y at two sites

Extended X-ray Absorption Fine Structure Studies of GaN Epilayers Doped in situ with Er and Eu During Molecular Beam Epitaxy

2003 ◽  
Vol 798 ◽  
Author(s):  
V. Katchkanov ◽  
J. F. W. Mosselmans ◽  
S. Dalmasso ◽  
K. P. O'Donnell ◽  
R. W. Martin ◽  
...  
Keyword(s):  
Fine Structure ◽  
Rare Earth ◽  
Molecular Beam Epitaxy ◽  
Local Structure ◽  
Molecular Beam ◽  
X Ray ◽  
Absorption Fine ◽  
X Ray Absorption ◽  
The Eu

ABSTRACTThe local structure around Er and Eu atoms introduced into GaN epilayers was studied by means of Extended X-ray Absorption Fine Structure above the appropriate rare-earth X-ray absorption edge. The samples were doped in situ during growth by Molecular Beam Epitaxy. The formation of ErN clusters was found in samples with high average Er concentrations of 32±6% and 12.4±0.8%, estimated by Wavelength Dispersive X-ray analysis. When the average Er concentration is decreased to 6.0±0.2%, 1.6±0.2% and 0.17±0.02%, Er is found in localised clusters of ErGaN phase with high local Er content. Similar behaviour is observed for Eu-doped samples. For an average Eu concentration of 30.5±0.5% clusters of pure EuN occur. Decreasing the Eu concentration to 10.4±0.5% leads to EuGaN clusters with high local Eu content. However, for a sample with an Eu concentration of 14.2±0.5% clustering of Eu was not observed.

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