Anomalous X-ray Scattering Research Articles

Fine structural analysis of calcium–niobium–gallium garnet (CNGG) by single-crystal anomalous X-ray scattering

Single-crystal anomalous X-ray scattering (AXS) experiments were conducted to investigate the cation distribution of calcium–niobium–gallium garnet (CNGG). AXS measurements suggested an ordered distribution of Nb at the octahedral site, and further structural refinement allowed us to obtain the structural formula Ca3Nb1.703(0) Ga3.162(2)O12. Ca was only located in the dodecahedral site, while Ga was distributed in the octa- and tetrahedral sites. The tetrahedral site had a significant number of vacancies at a ratio of one vacancy per unit cell, and the Nb/Ga occupation ratio at the octahedral site results in non-stoichiometric chemical composition of CNGG and its unique broad absorption wavelength.The findings of this study can contribute to device fabrication, property optimization, and quality control processes related to CNGG.

Evaluation of Semiconductors using Anomalous X-ray Scattering (2)

Evaluation of Semiconductors using Anomalous X-ray Scattering (2)

Formation of Iron Oxide Nanoparticles in the Internal Cavity of Ferritin-Like Dps Protein: Studies by Anomalous X-Ray Scattering

DNA-binding protein from starved cells (Dps) takes a special place among dodecamer mini-ferritins. Its most important function is protection of bacterial genome from various types of destructive external factors via in cellulo Dps–DNA co-crystallization. This protective response results in the emergence of bacterial resistance to antibiotics and other drugs. The protective properties of Dps have attracted a significant attention of researchers. However, Dps has another equally important functional role. Being a ferritin-like protein, Dps acts as an iron depot and protects bacterial cells from the oxidative damage initiated by the excess of iron. Here we investigated formation of iron oxide nanoparticles in the internal cavity of the Dps dodecamer. We used anomalous small-angle X-ray scattering as the main research technique, which allows to examine the structure of metal-containing biological macromolecules and to analyze the size distribution of metal nanoparticles formed in them. The contributions of protein and metal components to total scattering were distinguished by varying the energy of the incident X-ray radiation near the edge of the metal atom absorption band (the K-band for iron). We examined Dps specimens containing 50, 500, and 2000 iron atoms per protein dodecamer. Analysis of the particle size distribution showed that, depending on the iron content in the solution, the size of the nanoparticles formed inside the protein molecule was 2 to 4 nm and the growth of metal nanoparticles was limited by the size of the protein inner cavity. We also found some amount of iron ions in the Dps surface layer. This layer is very important for the protein to perform its protective functions, since the surface-located N-terminal domains determine the nature of interactions between Dps and DNA. In general, the results obtained in this work can be useful for the next step in studying the Dps phenomenon, as well as in creating biocompatible and solution-stabilized metal nanoparticles.

Study of Behavior of Supporting Electrolyte Ion of Fluoride Shuttle Battery Using Anomalous X‐Ray Scattering

Fluoride shuttle batteries (FSBs) are superior to lithium‐ion batteries (LIBs) in terms of high energy density, safety, etc. An electrolyte consisting of tetraglyme (G4) as a solvent molecule and triphenylboroxine (TPhBX) as an anion acceptor to improve the solubility of cesium fluoride (CsF) salt is a candidate of the electrolytes for FSBs. The low concentration of CsF in the electrolyte makes it difficult to study. Electrical X‐Ray total scattering and anomalous X‐Ray scattering (AXS) are powerful techniques for studying the local structures of electrolytes. This study shows that AXS measurement with a Cs K‐edge can clarify the local structure around very low atomic concentration (0.27 at%) Cs. The first‐neighbor distance and the coordination number suggest that Cs+ ions exist in the major Cs(G4)2+ complex together with the minor Cs(G4)+. The low‐Q peak observed in the scattering patterns can be attributed to the structure of alternating [TPhBX]F− and [Cs(G4)]+ (or [Cs(G4)2]+). The large sizes of cations ([Cs(G4)]+ and [Cs(G4)2]+) and anion [TPhBX]F− lead to a long correlation distance. This work presents the picture that the F− ions hop from TPhBX to [Cs(G4)]+ or [Cs(G4)2]+ toward the cathode and anode during charge and discharge, respectively.

Nucleation mechanisms in a SiO2-Li2O-P2O5-ZrO2 biomedical glass-ceramic: Insights on crystallisation, residual glasses and Zr4+ structural environment

In manufacturing reliable glass-ceramics, bulk chemistry and appropriate thermal treatments are critical points. To better understand the influence of nucleation parameters on the crystallisation behaviour and mechanical properties of multicomponent glass-ceramics, we studied the effects of time and temperature on phase stabilisation, the evolution of the crystal phases and physical properties of a Zr-rich lithium-silicate having a SiO2/Li2O molar ratio < 2. Here, we also provide insights into the structural environment of Zr4+ at the early stage of nucleation by Anomalous X-ray Scattering (AXS). By reverse-engineering a commercial material through remelting and sequential thermal treatments, we observed the strong effect of the nucleation temperature on the final mineral assemblage and of the volume fractions of the lithium-disilicate phase on the fracture toughness (KIc). Indeed, the KIc value was increased from ∼0.8 MPa.m½ in the pristine glass up to ∼ 2 MPa.m½, if compared to the original commercial material exhibiting a KIc value of 1.6 MPa.m½. Furthermore, the synthesis of residual glasses at different stages of the thermal treatments allowed us to observe the changes in the glass network structure and properties. AXS was used to extract the contribution exclusively coming from Zr for different nucleation steps. The differential pair distribution functions ΔZrg(r) show two distinct peaks at ∼2.10 Å and 3.44 Å, respectively associated with Zr-O and Zr-Zr/Zr-Si correlations with the formation of edge sharing in addition to corner sharing polyhedra. It was discerned the occurrence of (sub)nano-sized clusters enriched in Zr. These local clusters do not show changes during the different thermal treatments, either for higher temperatures or longer times. No Zr phases are stabilised in the crystallised materials, suggesting that these clusters do not evolve above the critical nucleus size. All evidence points to a highly heterogeneous environment and the coexistence of three structural regions i) (sub)nano Zr-clusters, ii) P enriched μ-areas, iii) residual silicate glass. The evolution and spatial distribution of these units influence the final properties.

Anomalous X-Ray Scattering and Extended X-Ray Absorption Fine Structure Study of the Local Structure of CrFeCoNiMox (x = 0.11, 0.18, and 0.23) High-Entropy Alloys

Anomalous x-ray scattering (AXS) and extended x-ray absorption fine structure (EXAFS) were used to determine the local structure of Mo in CrFeCoNiMox (x = 0.11, 0.18, and 0.23), a high-entropy alloy with a face-centered cubic (FCC) lattice. No superlattice peaks were observed down to the 10–4 intensity level. This observation along with the nearly constant decrease of the FCC diffraction peaks above the Mo K absorption edge suggests that Mo atoms have no preferred site occupancy in the FCC lattice. Modeling of the EXAFS data suggests a local chemical order in CrFeCoNiMox, where in Mo-rich samples (e.g., x = 0.23), Mo atoms are preferably surrounded by lighter atoms, such as Cr.

Generating Mechanism of Catalytic Effect for Hydrogen Absorption/Desorption Reactions in NaAlH4–TiCl3

The hydrogen desorption and absorption reactions of the complex metal hydride NaAlH4 are disproportionation processes, and the kinetics can be improved by adding a few mol% of Ti compounds, although the catalytic mechanism, including the location and state of Ti, remains unknown. In this study, we aimed to reveal the generating mechanism of catalytic Al–Ti alloy in NaAlH4 with TiCl3 using quantum multiprobe techniques such as neutron diffraction (ND), synchrotron X-ray diffraction (XRD), anomalous X-ray scattering (AXS), and X-ray absorption fine structure (XAFS). Rietveld refinements of the ND and XRD, profiles before the first desorption of NaAlD(H)4–0.02TiCl3 showed that Al in NaAlD(H)4 was partially substituted by Ti. On the other hand, Ti was not present in NaAlH4, and Al–Ti nanoparticles were detected in the XRD profile after the first re-absorption. This was consistent with the AXS and XAFS results. It is suggested that the substitution promotes the formation of a highly dispersed nanosized Al–Ti alloy during the first desorption process and that the effectiveness of TiCl3 as an additive can be attributed to the dispersion of Ti.

Evaluation of Semiconductors using Anomalous X-ray Scattering

Evaluation of Semiconductors using Anomalous X-ray Scattering

Fine Structure of Zr&lt;sub&gt;80&lt;/sub&gt;Pt&lt;sub&gt;20&lt;/sub&gt; Amorphous Alloy Determined from Anomalous X-ray Scattering (AXS) Data by Applying Reverse Monte-Carlo (RMC) Simulation Method

The fine structure of a Zr80Pt20 amorphous alloy was evaluated by anomalous X-ray scattering (AXS) coupled with reverse Monte Carlo (RMC) simulation. Featureless short-range ordered structures were preferentially formed by the Zr component, similar to those described by dense random packing (DRP), while the Pt atoms adopted a somewhat different structure. The Pt atoms adopted Zr-rich coordination and an icosahedral local atomic arrangement, in unique chemical short-range ordering (CSRO) as well as topological short-range ordering (TSRO). The present AXS-RMC analysis also suggested that the pre-peak signal at 17 nm−1 in the X-ray diffraction profile was largely attributed to the correlation between the Pt–Pt pair with a separation of approximately 0.4–0.5 nm. The geometrical and chemical features of the common neighbors of the middle-range Pt–Pt pairs indicate the unique CSRO and TSRO, where both chemical and density fluctuations were observed in two distinct regions: a Zr-rich region with high packing density and a Pt-rich region with low packing density.

Application of Anomalous X-ray Scattering Method to Liquid Electrolytes Used in a Battery: Local Structural Analysis around a Dilute Metallic Ion.

In liquid electrolytes used for a battery, various metal complexes are formed as a result of ion-solvent and ion-ion interactions, which strongly influence the properties of the electrolyte and thus the performance of the battery. Therefore, the structural characterization of such complexes is of great importance. In this study, the anomalous X-ray scattering (AXS) technique was applied to the potassium hydroxide solution including ∼0.3 mol % zinc, which is widely used in various batteries such as the alkaline battery. In spite of the small amount of the metallic ions, we have successfully extracted a local structure around zinc after careful data analysis. The obtained pair distribution function exhibited not only the short-range correlation corresponding to the Zn-O bond within the zincate anion but also a medium-range correlation above 3.5 Å. The present study demonstrates the capability of the AXS technique to detect local structures around dilute metallic ions in liquid electrolytes, which will largely extend the applicable range of this technique, especially to the field related to batteries.

Determination of Local Structures Around Trace Transition Elements in Minerals by Anomalous X-ray Scattering and X-ray Absorption Fine Structure Analyses

Determination of Local Structures Around Trace Transition Elements in Minerals by Anomalous X-ray Scattering and X-ray Absorption Fine Structure Analyses

The location of Mn and Fe in axinite–(Fe) from Nandan, China determined by anomalous X–ray scattering (AXS)

The location of Mn and Fe in axinite–(Fe) from Nandan, China determined by anomalous X–ray scattering (AXS)

Local- and Intermediate-Range Structures on Ordinary and Exotic Phase-Change Materials by Anomalous X-ray Scattering.

Local- and intermediate-range atomic structures were investigated on amorphous phases of an ordinary phase-change material, Ge2Sb2Te5 (GST), and an exotic one, Cu2GeTe3 (CGT), by using anomalous X-ray scattering close to K absorption edges of each element to find a fast amorphous-crystalline phase-change mechanism. The obtained data were analyzed by using reverse Monte Carlo modeling to obtain partial structure factors, partial pair distribution functions, and three-dimensional atomic configurations. Ring statistics were carefully examined to clarify the similarity and difference compared with the corresponding crystal structures, and it was found that amorphous GST has a number of four-membered rings indicating fragments of crystal structure, and amorphous CGT has a remarkable number of three-membered rings showing a collapse of crystal structures composed of purely six-membered rings. A persistent homology analysis was carried out and long-range ring structures of the constituent elements were observed in the amorphous phase, which may originate from fragments of crystal structures with a long-range periodicity.

Nanometer-Sized Crystalline Clusters of IGZO Films Determined from the Grazing Incidence X-ray Scattering and Anomalous X-ray Scattering Data Combined with Reverse Monte Carlo Simulations

Grazing incidence X-ray scattering measurements have been carried out on c-axis aligned crystalline-indium gallium zinc oxide (CAAC-IGZO) film and nanocrystalline category-indium gallium zinc oxide (NC-IGZO) film and the following results were obtained: (1) the characteristic layered structure of the IGZO crystal did not hold its shape and the X-ray scattering profile showed only a relatively sharp first peak at the wave vector (Q) = 21.8 for CAAC film and 23.1 nm−1 for NC film, respectively, and additional weak broad peaks were observed at a higher angle. (2) In the case of the CAAC film, tiny peaks were observed at Q = 7 and 14 nm−1, corresponding to the positions of the 003 and 006 reflections, respectively, of the IGZO crystal. Such tiny peaks were not detected in the case of NC film but the asymmetry of the first peak at the low angle side was clearly observed. (3) These structural features implied that more than three polyhedral units, such as InOx (x = 4–6), GaOy (y = 4–6), and ZnOz (z = 4–6), were likely to coexist. It is appropriate to call this structural feature as cluster-1. (4) A composite-type structure formed by combining these polyhedral units is also likely to exist and leads to middle-range ordering. This structure is called cluster-2. The size of such cluster-2 has been estimated to be 2.2 nm for CAAC film and 1.8 nm for NC film using the measured pair distribution function. To gain insights into the structural features of IGZO films, realistic atomic-scale models were obtained to fit not only the ordinary interference function of grazing incidence X-ray scattering but also the environmental interference function of the anomalous X-ray scattering (AXS) with Zn-absorption edge using reverse Monte Carlo (RMC) simulation. (5) The resultant models indicated the complex and irregular atomic arrangements of two types of IGZO films, which are well characterized by nanometer-sized crystalline clusters. This characteristic feature may be referred to as crystalline–cluster–composite (triple C) structure.

Multiple rare-earth ion environments in amorphous(Gd2O3)0.230(P2O5)0.770revealed by gadoliniumK-edge anomalous x-ray scattering

A Gd $K$-edge anomalous x-ray scattering (AXS) study is performed on the rare-earth $(R)$ phosphate glass, ${(\mathrm{G}{\mathrm{d}}_{2}{\mathrm{O}}_{3})}_{0.230}{({\mathrm{P}}_{2}{\mathrm{O}}_{5})}_{0.770}$, in order to determine $\mathrm{Gd}\ensuremath{\cdots}\mathrm{Gd}$ separations in its local structure. The minimum rare-earth separation is of particular interest given that the optical properties of these glasses can quench when rare-earth ions become too close to each other. To this end, a weak $\mathrm{Gd}\ensuremath{\cdots}\mathrm{Gd}$ pairwise correlation is located at $4.2(1)\phantom{\rule{0.16em}{0ex}}\AA{}$, which is representative of a metaphosphate $R\ensuremath{\cdots}R$ separation. More intense first-neighbor $\mathrm{Gd}\ensuremath{\cdots}\mathrm{Gd}$ pairwise correlations are found at the larger radial distributions, 4.8(1), 5.1(1), and $5.4(1)\phantom{\rule{0.16em}{0ex}}\AA{}$. These reflect a mixed ultraphosphate and metaphosphate structural character, respectively. A second-neighbor $\mathrm{Gd}\ensuremath{\cdots}\mathrm{Gd}$ pairwise correlation lies at $6.6(1)\phantom{\rule{0.16em}{0ex}}\AA{}$ which is indicative of metaphosphate structures. Meta- and ultraphosphate classifications are made by comparing the $R\ensuremath{\cdots}R$ separations against those of rare-earth phosphate crystal structures, $R{(\mathrm{P}{\mathrm{O}}_{3})}_{3}$ and $R{\mathrm{P}}_{5}{\mathrm{O}}_{14}$, respectively, or difference pair-distribution function $(\mathrm{\ensuremath{\Delta}}\mathrm{PDF})$ features determined on similar glasses using difference neutron-scattering methods. The local structure of this glass is therefore found to display multiple rare-earth ion environments, presumably because its composition lies between these two stoichiometric formulae. These $\mathrm{Gd}\ensuremath{\cdots}\mathrm{Gd}$ separations are well-resolved in $\mathrm{\ensuremath{\Delta}}\mathrm{PDFs}$ that represent the AXS signal. Indeed, the spatial resolution is so good that it also enables the identification of $R\ensuremath{\cdots}X\phantom{\rule{4pt}{0ex}}(X=R$, P, O) pairwise correlations up to $r\ensuremath{\sim}9\phantom{\rule{0.16em}{0ex}}\AA{}$; their average separations lie at $r\ensuremath{\sim}7.1(1)$, 7.6(1), 7.9(1), 8.4(1), and $8.7(1)\phantom{\rule{0.16em}{0ex}}\AA{}$. This is a report of a Gd $K$-edge AXS study on an amorphous material. Its demonstrated ability to characterize the local structure of a glass up to such a long range of $r$ heralds exciting prospects for AXS studies on other ternary noncrystalline materials. However, the technical challenge of such an experiment should not be underestimated, as is highlighted in this work where probing AXS signal near the Gd $K$ edge is found to produce inelastic x-ray scattering that precludes the normal AXS methods of data processing. Nonetheless, it is shown that AXS results are not only tractable but they also reveal local structure of rare-earth phosphate glasses that is important from a materials-centered perspective and which could not be obtained by other materials characterization methods.

Crystal structure of the λ-Al13Fe4-type intermetallic (Al,Cu)13(Fe,Cu)4

An (Al,Cu)13(Fe,Cu)4phase of [trideca(aluminium/copper) tetra(iron/copper)] was obtained by the high-pressure sintering (HPS) process of a mixture with composition Al78Cu15Fe7. Structure analysis suggests that Cu atoms can replace both Al and Fe atoms. Such findings support previous anomalous X-ray scattering (AXS) results although deviate from other reports. The new phase adopts the λ-Al13Fe4structure type where Cu atoms partially occupy the 2cand 4isites for Al and Fe atoms, respectively, with occupancies of 0.233 (5) and 0.173 (16).

Anomalous X-ray Scattering on Semiconducting Glasses at ESRF: Review in Recent Fifteen Years

Abstract The most difficult issue for the structural characterizations for non-crystalline multi-component materials is to determine partial structures because n(n + 1)/2 scattering experiments with different scattering cross-sections are necessary for n-component materials. More than three decades have already passed through since anomalous X-ray scattering (AXS) using synchrotron radiation (SR) was expected as a promising tool for investigating partial structures. Compared with a related method, X-ray absorption fine structure, however, AXS is still rarely used owing to difficulties in the experiments and data analyses. We have developed a new detecting system, which can fully utilize intense X-ray fluxes from third-generation SR facilities. Using this detecting system, we have carried out many AXS experiments at the beamline BM02 of the ESRF on several semiconducting glasses. The obtained differential structure factors were analyzed using reverse Monte Carlo modeling to draw three-dimensional atomic configurations. In this article, we review results of semiconducting glasses, and describe the structure-property relations in these glasses.

Structural Aspects of the Superionic Conduction Mechanism in Ag-GeSe3 Glasses

Abstract The local and intermediate-range atomic structure in the Ag ion conducting glasses Ag x (GeSe3)1−x with x = 0.15 and 0.50 has been investigated by Anomalous X-Ray Scattering experiments at the K absorption edges of each constituent element. This method can provide insight into the structural properties enabling the effect of superionic conductivity for compositions with x &gt; 0.33 in the amorphous phase. The experimental results were analyzed with Reverse Monte Carlo modeling, providing the partial structure factors and the corresponding partial pair-distribution functions. Evidence is found for a high level of intermediate range order for low silver concentrations, whereas the superionic conducting phase formed at high silver concentrations is characterized by cluster-like configurations of Ag atoms on a nanometer scale.

Anomalous X-Ray Scattering on Chalcogenide Glasses

ABSTRACTIn this article, we review our recent structural studies on chalcogenide glass systems, GexSe1-x and AsxSe1-x, using anomalous X-ray scattering (AXS) in combination with reverse Monte Carlo (RMC) modeling. We show to what extent the present AXS + RMC works are effective to solve the long lasting topics in these chalcogenide glasses, such as the validity of the 8-N bonding rule, the relation to the rigidity percolation theory, the validity of chemical order, and the origin of prepeak.

Microscopic Structure Analysis in Disordered Materials using Anomalous X-ray Scattering

Abstract Although X-ray diffraction is still mainly used to determine crystal structures, the demand for an understanding of the atomic arrangement in disordered matter has progressively become more important over the past decades. However, apart from simple model systems, it is still a challenging task to unravel the microscopic ordering of the atoms in amorphous multi-component materials, although this knowledge becomes increasingly important in modern materials science, in which the physical properties are often related to the microscopic ordering of the different chemical species of the substance. This article reports about the combination of Anomalous X-ray Scattering (AXS) with Reverse Monte Carlo Computer simulation (RMC) as a proper tool to precisely determine the microscopic structural characteristics in such systems with high reliability. The basic principles of the method will be illustrated and some examples of modern materials will be given to proof the applicability and the capability of this method.