Search results for "extended X-ray absorption fine structure"
showing 10 items of 193 documents
X-ray absorption study of Ce?Ti oxide films
2001
Abstract X-ray absorption measurements at the Ce L 3 , L 1 and Ti K-edges have been done to study local structure and electronic properties of CeO 2 –TiO 2 thin films produced by reactive d.c. magnetron sputtering. The local environment around titanium and cerium ions can be described as pyramid-like and cube-like polyhedra, respectively, and the films are amorphous (correlation radius about 10 A). The analysis of Ce L 3 -edge XANES data has shown that the position of the Ce 4f 1 5d and 4f 0 5d states progressively shift towards lower energies with decreasing cerium dioxide content in the thin films.
Wavelet data analysis of EXAFS spectra
2009
Abstract The application of wavelet transform to the analysis of the extended X-ray absorption fine structure (EXAFS) from perovskite-type compounds is presented on the example of the Re L 3 -edge in ReO 3 and Co K-edge in LaCoO 3 . We propose a modified wavelet transform procedure, which allows better discrimination of the overlapped contributions into the EXAFS signal.
XRD and XAS structural study of CuAlO2under high pressure
2013
International audience; We present the results of x-ray diffraction and x-ray absorption spectroscopy experiments in CuAlO2 under high pressure. We discuss the polarization dependence of the x-ray absorption near-edge structure at the Cu K-edge. XRD under high pressure evidences anisotropic compression, the a-axis being more compressible than the c-axis. EXAFS yields the copper-oxygen bond length, from which the only internal parameter of the delafossite structure is deduced. The combination of anisotropic compression and the internal parameter decrease results in a regularization of the AlO6 octahedra. The anisotropic compression is related to the chemical trends observed in the lattice pa…
Proton Dynamics in In:BaZrO3: Insights on the Atomic and Electronic Structure from X-ray Absorption Spectroscopy
2009
The local structure of Ba2+, Zr4+, and In3+ in In:BaZrO3 is investigated with EXAFS for samples having 0 to 75% In3+ content. It is found that indium can be inserted in any ratio in the host matrix oxide and that the oxygen coordination shell displays an In-O distance very similar to the Zr-O length. In the Zr-rich compositions, there is a preferred dopant-vacancy association that, however, does not give rise to dopant-proton interaction in the hydrated samples. The tendency of Ba2+ to be attracted toward the dopant site is attributed to the electrostatic interaction with the dopant and to the structural rearrangement around the In3+ site. Third cumulant analysis at high temperatures (up to…
<title>Local structure of Ta-Re mixed oxide thin films studied by x-ray absorption spectroscopy</title>
2003
Mixed Ta-Re oxide thin films were synthesized for the first time by dc magnetron co-sputtering. Local environment around tantalum and rhenium atoms was studied by the Ta and Re L3-edges x-ray absorption spectroscopy in pure Ta2O5 and mixed Ta-Re oxide thin films (Ta:Re = 50:50, 38:62, 20:80 as determined from the ratio of the Ta-to-Re absorption edges). It was found that rhenium atoms are four-fold coordinated by oxygen atoms with R(Re-O) = 1.74 ± 0.01 Å and the mean square relative displacement (MSRD) σ2 = 0.0012 ± 0.0005 Å2. In pure Ta2O5 thin film, tantalum ions are coordinated by six oxygen atoms at R(Ta-O) = 2.02 ± 0.01 Å with the MSRD σ2 = 0.010 ± 0.001 Å2. The addition of rhenium ion…
Origin of Pressure-Induced Metallization in Cu 3 N: An X-ray Absorption Spectroscopy Study
2018
The authors are grateful to Professor Alain Polian for providing the NDAC cell.
Using photoelectron emission microscopy with hard-X-rays
2001
We present several successful test cases of using photoelectron emission microscopy (PEEM) for photon energy up to 25 keV. First, the full extended X-ray absorption fine structure analysis was implemented in areas as small as 100 mum(2) for transition-metal K edge absorption spectra and, therefore, demonstrated the feasibility of combining structural and chemical analysis with hard-X-ray absorption spectroscopy with high lateral resolution. We also show that PEEM can be used in a transmission (radiography) mode as an imaging detector for hard-X-ray, This approach again leads to the unprecedented 0.3 mum lateral resolution, particularly critical for the use of coherence-based phase contrast …
Preparation and XAFS studies of organotin(IV) complexes with adenosine and related compounds and calf thymus DNA
2007
Complexes of adenosine and related compounds (adenosine-5’-monophosphate, adenosine-5’-triphosphate and pyridoxal-5-phosphate) with Bu2SnO and/or BuSnCl2 were prepared in the solid state. The compositions of the complexes were determined by standard analytical methods. It was found that the complexes contain the organotin(IV) moiety and the ligand in a ratio of 1:1. The FT-IR spectra demonstrated that Bu2SnO reacts with the D-ribose moiety of the ligands, while Bu2SnCl2 is coordinated to the deprotonated phosphate group. The basic part of the ligands does not participate directly in complex formation. Comparison of the experimental Mossbauer Δ (quadrupole splitting) values with those calcul…
A Study Using X-ray Absorption and Emission Spectroscopy of Dioxygen-Binding Xerogels Incorporating Cyclam Units Complexed with Copper Salts.
2005
X-ray absorption spectroscopy was used to elucidate how hybrid xerogels complexed with CuCl2 could reversibly bind molecular dioxygen. Difference EXAFS analyses at the Cu K-edge suggest that dioxygen could bridge two Cu atoms in a μ-η1:η1 peroxo-like conformation with unequal Cu···O distances. Only the short distance (RCu–O1 = 1.86 ± 0.01 A) was unambiguously determined and looks typical of a CuII site. The Cu···Cu internuclear distances would be rather long: RCu–Cu ≈ 4.0 A (3.9 A) for the oxygenated (oxygen-free) xerogels. Cl K-edge EXAFS spectra revealed the pre-existence in the oxygen-free xerogels of CuI sites with short Cl–Cu bonds (2.11 ± 0.03 A). Pentacoordinate CuII sites with a lon…
Single crystal EXAFS at high pressure
2000
Abstract We present a new technique for structure characterization under high pressure conditions. The use of an undulator beam of the third-generation ESRF source of synchrotron radiation has enabled the first single crystal EXAFS experiments at high pressure using a diamond anvil cell as pressure generator. Taking advantage of the linear polarization of X-rays the technique becomes an orientation-selective probe of the local structure of materials. We describe the principle of the technique and some applications.