Covalence of chemical bonds and white-line intensity of an L 3-edge X-ray absorption near-edge structure of rare earth elements embedded in glass

2009 ◽  
Vol 15 (6) ◽  
pp. 993-999 ◽  
Author(s):  
Yong Gyu Choi
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Line Intensity ◽  
Chemical Bonds ◽  
White Line ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption

Fluorescence Extended X-Ray Absorption Fine Structure Study on Local Structures of Rare-Earth-Doped InGaGdN

2016 ◽  
Vol 1133 ◽  
pp. 429-433
Author(s):  
Siti Nooraya Mohd Tawil ◽  
Shuichi Emura ◽  
Daivasigamani Krishnamurthy ◽  
Hajime Asahi
Keyword(s):  
Fine Structure ◽  
Rare Earth ◽  
Nearest Neighbor ◽  
Structure Study ◽  
Edge Structure ◽  
X Ray ◽  
Local Structures ◽  
Absorption Fine ◽  
X Ray Absorption

Local structures around gadolinium atoms in rare-earth (RE)-doped InGaGdN thin films were studied by means of fluorescence extended X-ray absorption fine structure (EXAFS) measured at the Gd LIII-edges. The samples were doped with Gd in-situ during growth by plasma-assisted molecular beam epitaxy (PAMBE). Gd LIII-edge EXAFS signal from the GaGdN, GdN and Gd foil were also measured as reference. The X-ray absorption near edge structure (XANES) spectra around Gd LIII absorption edge of InGaGdN samples observed at room temperature indicated the enhancement of intensities with the increase of Gd composition. Further EXAFS analysis inferred that the Gd atoms in InGaN were surrounded by similar atomic shells as in the case of GaGdN with the evidence indicating majority of Gd atoms substituted into Ga sites of InGaGdN. A slight elongation of bond length for the 2nd nearest-neighbor (Gd–Ga) of sample with higher Gd concentration was also observed.

X-Ray Absorption Studies of La2−xSrxCuO4 and Y1−xPrxBa2Cu3O7-δ

1987 ◽  
Vol 99 ◽  
Author(s):  
E. E. Alp ◽  
G. K. Shenoy ◽  
L. Soderholm ◽  
G. L. Goodman ◽  
D. G. Hinks ◽  
...  
Keyword(s):  
Rare Earth ◽  
Cross Section ◽  
Atomic Clusters ◽  
Oxide Superconductors ◽  
Absorption Cross ◽  
Edge Structure ◽  
X Ray ◽  
Absorption Studies ◽  
High Transition ◽  
X Ray Absorption

ABSTRACTThe question of valence of Cu and rare-earth atoms in the newly discovered oxide superconductors with high transition temperatures is crucial to the understanding of their electronic structure. We have measured the X-Ray Absorption Near Edge Structure (XANES) of Cu K transition and Pr Ljjj transition to obtain information on the valence of Cu, and Pr in La2−xSrxCuO4 and Y1−xPrxBa2Cu3O7-δ. We will present the experimental results, compare them with calculations of absorption cross-section for model atomic clusters, and discuss the valence of Cu as a function of oxygen concentration.

scholarly journals Anisotropy of Chemical Bonds in Collagen Molecules Studied by X-ray Absorption Near-Edge Structure (XANES) Spectroscopy

2011 ◽  
Vol 7 (3) ◽  
pp. 476-480 ◽  
Author(s):  
Raymond S.K. Lam ◽  
Rebecca A. Metzler ◽  
Pupa U.P.A. Gilbert ◽  
Elia Beniash
Keyword(s):  
Xanes Spectroscopy ◽  
Chemical Bonds ◽  
Edge Structure ◽  
X Ray ◽  
Collagen Molecules ◽  
X Ray Absorption

scholarly journals An X-ray absorption method for the identification of calcium phosphate species using peak height ratios

2013 ◽  
Vol 10 (11) ◽  
pp. 18723-18756 ◽  
Author(s):  
J. F. Oxmann
Keyword(s):  
Calcium Phosphate ◽  
Peak Height ◽  
Apatite Formation ◽  
Spectral Features ◽  
White Line ◽  
Edge Structure ◽  
X Ray ◽  
Compound Libraries ◽  
Phosphate Species ◽  
X Ray Absorption

Abstract. X-ray absorption near edge structure (XANES) studies on calcium phosphate species (Ca-P) deal with marginal differences among subtle spectral features despite a hitherto missing systematic breakdown of these differences. Related fingerprinting approaches depend therefore on spectral libraries that are not validated against each other, incomplete and scattered among publications. This study compiled a comprehensive spectral library from published reference compound libraries in order to establish more clear-cut criteria for Ca-P determination by distinctive phosphorus K-edge XANES features. A specifically developed normalization method identified diagnostic spectral features within the compiled library, e.g. by uniform calculation of ratios between white-line and secondary peak heights. Post-processing of the spectra (n = 81) verified distinguishability among most but not all phases, which included hydroxylapatite (HAP), poorly crystalline HAP, amorphous HAP, fluorapatite, carbonate fluorapatite (CFAP), carbonate hydroxylapatite, β-tricalcium phosphate, octacalcium phosphate (OCP), brushite, monetite, monocalcium phosphate, amorphous calcium phosphate (ACP), anapaite, herderite, scholzite, messelite, whiteite and P on CaCO3. Particularly, peak height ratios significantly improved analyte specificity, e.g. by supplementary breakdown into OCP and ACP. The spectral analysis also revealed Ca-P standards that were rarely investigated or inappropriately synthesized, and thus provides a basis for standard selection and synthesis. The developed method and resulting breakdown by species were subsequently tested on Ca-P spectra from studies on bone and sediment. The test indicated that bone material likely comprises only poorly crystalline apatite, which implies direct nucleation of apatite in bone. This biological apatite formation is likely opposed to that of sedimentary apatite, which apparently forms by successive crystallization. Application of the method to μXANES spectra of sediment particles indicated authigenic apatite formation by an OCP precursor.

Tb L3-edge X-ray Absorption Near-edge Structure Spectroscopic Analysis of Terbium-doped Phosphor Compoundsfor Plasma Display Panel Applications

2002 ◽  
Vol 17 (1) ◽  
pp. 31-35 ◽  
Author(s):  
Yong Gyu Choi ◽  
Kee-Sun Sohn ◽  
Kyong Hon Kim ◽  
Hee Dong Park
Keyword(s):  
Spectroscopic Analysis ◽  
Green Emission ◽  
Concentration Quenching ◽  
Plasma Display Panel ◽  
White Line ◽  
Edge Structure ◽  
X Ray ◽  
Line Absorption ◽  
Plasma Display ◽  
X Ray Absorption

We have analyzed Tb L3-edge x-ray absorption near-edge structure spectra of Tb-doped phosphor compounds for plasma display panel applications. Intensity and lifetime of the green emission from the Tb3+:5D4→7F5 transition were measured with respect to nominal terbium concentration in the host compounds, i.e., YBO3, YPO4,and Y4Al2O9, all of which were made through the solid-state reaction. Typical concentration quenching was evident on the fluorescence intensity and the fluorescing level lifetime in our samples. From the analyses of white line absorption peaks at TbL3-edge, it was verified that terbium is essentially trivalent in all the samples, even invery highly concentrated ones. Thus, this implies that the concentration quenching was not caused by presence of mixed-valent states of terbium. Instead, it is believed that anonradiative energy transfer route among Tb3+ ions might be responsible for thebehavior.

Effect of gamma irradiation on X-ray absorption and photoelectron spectroscopy of Nd-doped phosphate glass

2016 ◽  
Vol 23 (6) ◽  
pp. 1424-1432 ◽  
Author(s):  
V. N. Rai ◽  
Parasmani Rajput ◽  
S. N. Jha ◽  
D. Bhattacharyya ◽  
B. N. Raja Shekhar ◽  
...  
Keyword(s):  
Gamma Irradiation ◽  
Photoelectron Spectroscopy ◽  
Glass Matrix ◽  
Structural Changes ◽  
Phosphate Glasses ◽  
White Line ◽  
Edge Structure ◽  
Xps Spectra ◽  
X Ray ◽  
X Ray Absorption

X-ray absorption near-edge structure (XANES) and X-ray photoelectron spectroscopy (XPS) of Nd-doped phosphate glasses have been studied before and after gamma irradiation. The intensity and the location of the white line peak of theL3-edge XANES of Nd are found to be dependent on the ratio O/Nd in the glass matrix. Gamma irradiation changes the elemental concentration of atoms in the glass matrix, which affects the peak intensity of the white line due to changes in the covalence of the chemical bonds with Nd atoms in the glass (structural changes). Sharpening of the Nd 3d5/2peak profile in XPS spectra indicates a deficiency of oxygen in the glasses after gamma irradiation, which is supported by energy-dispersive X-ray spectroscopy measurements. The ratio of non-bridging oxygen to total oxygen in the glass after gamma radiation has been found to be correlated to the concentration of defects in the glass samples, which are responsible for its radiation resistance as well as for its coloration.

scholarly journals Random Forest Machine Learning Models for Interpretable X-Ray Absorption Near-Edge Structure Spectrum-Property Relationships

2020 ◽  
Author(s):  
Steven Torrisi ◽  
Matthew Carbone ◽  
Brian Rohr ◽  
Joseph H. Montoya ◽  
Yang Ha ◽  
...  
Keyword(s):  
Machine Learning ◽  
Functional Materials ◽  
Learning Models ◽  
Linear Quadratic ◽  
White Line ◽  
Edge Structure ◽  
Line Energy ◽  
X Ray ◽  
X Ray Absorption ◽  
Machine Learning Models

X-ray absorption spectroscopy (XAS) produces a wealth of information about the local structure of materials, but interpretation of spectra often relies on easily accessible trends and prior assumptions about the structure. Recently, researchers have demonstrated that machine learning models can automate this process to predict the coordinating environments of absorbing atoms from their XAS spectra. However, machine learning models are often difficult to interpret, making it challenging to determine when they are valid and whether they are consistent with physical theories. In this work, we present three main advances to the data-driven analysis of XAS spectra: we demonstrate the efficacy of random forests in solving two new property determination tasks (predicting Bader charge and mean nearest neighbor distance), we show that multiscale featurization can elucidate the regions and trends in spectra that encode various local properties, and we address the effect of normalization on model interpretability. The multiscale featurization transforms the spectrum into a vector of polynomial-fit features, and is contrasted with the commonly-used "pointwise" featurization that directly uses the entire spectrum as input. We find that across thousands of transition metal oxide spectra, the relative importance of features describing the curvature of the spectrum can be localized to individual energy ranges, and we can separate the importance of constant, linear, quadratic, and cubic trends, as well as the white line energy. This work has the potential to assist rigorous theoretical interpretations, expedite experimental data collection, and automate analysis of XAS spectra, thus accelerating discovery of new functional materials.

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