X-ray Absorption Fine Structure experiments conducted at synchrotron facilities are currently limited by the performance of the current generation of Silicon and Germanium detectors. In order to mitigate this limitation, the detector consortium of the European project LEAPS-INNOV has undertaken an ambitious R&D program devoted to develop a new generation of multi-element monolithic Germanium detectors for X-ray detection. Two detector prototypes are currently being developed and are expected to be commissioned end of 2024. After a brief introduction to the project, the paper will focus on the efforts to evaluate and optimize the performance of the prototypes using a full simulation chain developed within the framework of the LEAPS-INNOV project. These evaluations demonstrate that by combining a collimator, with cross-talk corrections and charge sharing rejection in the digital pulse processor, a signal-to-background ratio greater than 1000 could be attained in the energy range of interest from 5 keV to 100 keV.

In past years efforts have concentrated on the development of arrays of Silicon Drift Detectors for X-ray spectroscopy. This is in stark contrast to the little effort that has been devoted to the improvement of germanium detectors, in particular for synchrotron applications. Germanium detectors have better energy resolution and are more efficient in detecting high energy photons than silicon detectors. In this context, the detector consortium of the European project LEAPS-INNOV has set an ambitious R&D program devoted to the development of a new generation of multi-element monolithic germanium detectors for X-ray detection. In order to improve the performance of the detector under development, simulations of the different detector design options have been performed. In this contribution, the efforts in terms of R&D are outlined with a focus on the modelization of the detector geometry and first performance results. These performance results show that a signal-to-background ratio larger than 1000 can be achieved in the energy range of interest from 5 keV to 100 keV.

Abstract Band structure tailoring has been a great avenue to achieve the half-metallic electronic ground state in materials. Applying this approach to the full Heusler alloy Fe2TiSn, Cr is introduced systematically at Ti site that conforms to the chemical formula $${\text{Fe}}_{2} {\text{Ti}}_{{1 - x}} {\text{Cr}}_{x}$$ Fe 2 Ti 1 - x Cr x Sn. Compositions so obtained have been investigated for its electronic, magnetic, and electrical transport properties with an aim to observe the half-metallic ferromagnetic ground state, anticipated theoretically for Fe2CrSn. Our experimental study using synchrotron X-ray diffraction reveals that only compositions with $$x \le$$ x ≤ 0.25 yield phase pure L2 $$_1$$ 1 cubic structures. The non-magnetic ground state of Fe2TiSn gets dramatically affected upon inclusion of Cr giving rise to a localized magnetic moment in the background of Ruderman–Kittel–Kasuya–Yosida (RKKY) correlations. The ferromagnetic interactions begin to dominate for x = 0.25 composition. Results of its resistivity and magnetoresistance (MR) measurement point towards a half-metallic ground state. The calculation of exchange coupling parameter, $$\hbox {J}_{{ij}}$$ J ij , and orbital projected density of states that indicate a change in hybridization between 3d and 5p orbital, support the observations made from the study of local crystal structure made using the extended X-ray absorption fine structure spectroscopy. Our findings here highlight an interesting prospect of finding half-metallicity via band structure tailoring for wide application in spintronics devices.

We present a new autoclave that enables in situ characterization of hydrothermal fluids at high pressures and high temperatures at synchrotron x-ray radiation sources. The autoclave has been specifically designed to enable x-ray absorption spectroscopy in fluids with applications to mineral solubility and element speciation analysis in hydrothermal fluids in complex compositions. However, other applications, such as Raman spectroscopy, in high-pressure fluids are also possible with the autoclave. First experiments were run at pressures between 100 and 600 bars and at temperatures between 25 °C and 550 °C, and preliminary results on scheelite dissolution in fluids of different compositions show that the autoclave is well suited to study the behavior of ore-forming metals at P-T conditions relevant to the Earth's crust.

Transparent n-type niobium-doped titanium dioxide thin films (TiO2:1.5 at.%Nb) with pronounced thermoelectric properties were produced from a composite Ti:Nb target by reactive magnetron sputtering. The thin films were comprehensively characterized by X-ray diffraction, X-ray photoelectron spectroscopy, optical spectroscopy, electrical conductivity, and thermoelectric measurement techniques. The local structure of the thin films was investigated in detail by X-ray absorption spectroscopy at the Ti and Nb K-edges. A set of radial distribution functions were extracted from the simultaneous analysis of EXAFS data at two absorption edges using the reverse Monte Carlo method. It was found that Nb dopant atoms modify the local environment of the films, but their average structure remains close to that of the anatase phase. This conclusion is also supported by the ab initio simulations of XANES. A very high absolute Seebeck coefficient (S = 155 μV/K) for n-type TiO2 was achieved with Nb doping, yielding a maximum power factor and thermoelectric figure of merit of 0.5 mW m−1 K−2 and 0.18 at a temperature of 300 K, respectively, for a 150 nm thick film. From frequency-domain thermoreflectance experiments, a thermal conductivity value of 1.3 W m−1 K−1 was obtained for the optimized TiO2:Nb film.

The structure of Ge20Sb10S70, Ge23Sb12S65 and Ge26Sb13S61 glasses was investigated by neutron diffraction (ND), X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS) measurements at the Ge and Sb K-edges as well as Raman scattering. For each composition, large scale structural models were obtained by fitting simultaneously diffraction and EXAFS data sets in the framework of the reverse Monte Carlo (RMC) simulation technique. Ge and S atoms have 4 and 2 nearest neighbors, respectively. The structure of these glasses can be described by the chemically ordered network model: Ge-S and Sb-S bonds are always preferred. These two bond types adequately describe the structure of the stoichiometric glass while S-S bonds can also be found in the S-rich composition. Raman scattering data show the presence of Ge-Ge, Ge-Sb and Sb-Sb bonds in the S-deficient glass but only Ge-Sb bonds are needed to fit diffraction and EXAFS datasets. A significant part of the Sb-S pairs has 0.3-0.4 angstrom longer bond distance than the usually accepted covalent bond length (similar to 2.45 angstrom). From this observation it was inferred that a part of Sb atoms have more than 3 S neighbors. (C) 2018 Elsevier B.V. All rights reserved.

We present element-specific effective bond-stretching force constants and Einstein frequencies of (In,Ga)P ternary alloys determined by temperature-dependent extended x-ray absorption fine structure spectroscopy. The bond-stretching force constants of both bond species show a nearly linear composition dependence between the values of GaP and InP. In contrast, the corresponding Einstein frequencies are different for the two bond species over the whole compositional range. Furthermore, we demonstrate that the composition dependence of bond-stretching force constants and Einstein frequencies for (In,Ga)P, (In,Ga)As, and Zn(Se,Te) is mostly caused by the associated bond length changes. Remaining deviations may be explained by coupling effects between different bond species within the alloy. Copyright (C) EPLA, 2019

The development of new generations of synchrotron light sources aims at increasing their beam in term of flux and brightness. To cope with extremely high-brilliance sources, fluorescence detectors must go beyond their nowadays maximum throughput while keeping almost unchanged the performance. This paper has been carried out within the framework of the ARDESIA (ARray of DEtectors for Spectroscopy and Imaging Applications) project, whose primary aim is to develop a spectrometer with count-rate capability for applications like Xray absorption spectroscopy (XAS) and X-ray fluorescence (XRF). ARDESIA is a Silicon Drift Detector (SDD)-based, multichannel X-ray spectrometer, optimized for synchrotron applications requiring a high-count rate (>1Mcps per channel) and a high-resolution (e.g. below 150 eV of Full Width Half Maximum at peaking times faster than 200 ns) for X-ray fluorescence detection. This paper describes improvements made for the ARDESIA spectrometer on detection efficiency and overall counting rate capability to better match requirements of synchrotron experiments. These improvements have been obtained by increasing the number of channels, from 4 to 16, and the SDD thickness from 450 mu m to 800 mu m and 1000 mu m. The new detection module and the new complete spectrometer are described in detail. The first 16-channel detection module prototype has been developed with an average resolution of 128 eV at the Mn-K alpha at long peaking times (i.e. > 2 mu s) and 183.5 eV at short peaking time (i.e. 32 ns). Then, the qualification of the 4-channel 1mm-thick detector at the PETRA (Positron-Elektron-Tandem-Ring-Anlage) P65 beamline in DESY (Deutsches Elektronen-Synchrotron) is reported.

The surface chemistry and bulk chemical speciation of solid industrial wastes containing 8wt-% antimony (Sb) were investigated using synchrotron X-ray Absorption Near Edge Structure (XANES) and Time-of-Flight Ion Secondary Mass Spectrometry (ToF-SIMS). Leaching experiments were conducted in order to better understand the behavior of Sb in waste streams and to inform regulatory management of antimony-containing wastes. The experiments also demonstrate how a combination of XANES and ToF-SIMS adds value to the field of waste investigations. Leaching treatments (acid and base) were performed at a synchrotron over 24h time periods. Surface analyses of the wastes before leaching showed the presence of Sb associated with S and O. Bulk analyses revealed Sb to be present, primarily, as trivalent sulfide species. Both acid and base leaching did not change the antimony speciation on the solid. Leaching transferred about 1% of the total Sb into solution where Sb was found to be present as Sb(V). XANES data showed similarities between leachate and FeSbO4. During base leaching, the Sb content in solution gradually increased over time, and potential desorption mechanisms are discussed.

Lithium reactive hydride composite 2LiBH(4) + MgH2 (Li-RHC) has been lately investigated owing to its potential as hydrogen storage medium for mobile applications. However, the main problem associated with this material is its sluggish kinetic behavior. Thus, aiming to improve the kinetic properties, in the present work the effect of the addition of Fe to Li-RHC is investigated. The addition of Fe lowers the starting decomposition temperature of Li-RHC about 30 degrees C and leads to a considerably faster isothermal dehydrogenation rate during the first hydrogen sorption cycle. Upon hydrogenation, MgH2 and LiBH4 are formed whereas Fe appears not to take part in any reaction. Upon the first dehydrogenation, the formation of nanocrystalline, well distributed FeB reduces the overall hydrogen storage capacity of the system. Throughout cycling, the agglomeration of FeB particles causes a kinetic deterioration. An analysis of the hydrogen kinetic mechanism during cycling shows that the hydrogenation and dehydrogenation behavior is influenced by the activity of FeB as heterogeneous nucleation center for MgB2 and its non-homogenous distribution in the Li-RHC matrix. (C) 2015 Elsevier B.V. All rights reserved.

The existence and effect of different rare earth (R2+/3+/IV) ions in SrAl2O4:Eu2+,R3+ and M2MgSi2O7:Eu2+,R3+ (M: Sr, Ba) persistent luminescence materials was studied with XANES (x-ray absorption near edge structure) measurements at HASYLAB/DESY (Hamburg, Germany) and MAX-lab (Lund, Sweden). The experiments were carried out at 298 K for selected rare earth (co-)dopants (Eu2+; Ce3+, Nd3+, Sm3+, Dy3+ and Yb3+). The co-existence of Eu2+ and Eu3+ was observed in all materials. The co-dopants were always in the trivalent form.

Spray deposition of thin films and coatings is a widely used manufacturing process owing to its low cost, versatility and simple implementation. The objective of the presented experiments was to investigate whether X-ray absorption measurements on solutes carried by aerosols are possible, and what count rates can be achieved depending on solution flow through and the resulting mass density in the interrogation volume. The investigated prototypical spray aerosol was InCl3dissolved in water or ethanol dispersedviaan ultrasonic nebulizer. InCl3spray is essential for the ion layer gas reaction process used for the deposition of In2S3buffer layers for highly efficient chalcopyrite solar cells. The discussed experiments demonstrate that measurements are possible, but that the achievement of good signal-to-noise ratios requires extended sampling times and concentrated solutions.

Light weight metal hydrides are favoured materials for hydrogen storage in mobile and stationary applications. Due to the high requirements on the materials concerning storage capacity, reaction thermodynamics and kinetics novel functional materials need to be developed. One promising new class of materials are the Reactive Hydride Composites (RHC) [1,2]. These systems show reduced total reaction enthalpies at high storage capacities. The system of e.g. 2LiH + MgB2 + 4H2↔ 2LiBH4 + MgH2 has a theoretical storage capacity of 11.4 wt% hydrogen and an equilibrium pressure of 1bar H2 at 170°C. Another very promising system with respect to thermodynamics and kinetics is the composite of CaH2 + MgB2 + 4H2↔ Ca(BH4)2 + MgH2. During the endothermic desorption reaction the exothermic formation of MgB2 proceeds and thereby lowers the total reaction enthalpy. The systems show very sluggish kinetics and can therefore only be operated at temperatures very much above the thermodynamic equilibrium. With cycling and suitable additives the kinetics is improved by an order of magnitude [3]. Characterization of these additives, their chemical state and distribution is the key to understanding the mechanism behind.

In YMn2O5, the Mn atoms occupy two nonequivalent Wyckoff sites within the unit cell exhibiting different oxygen coordinations, i.e., the system can be characterized as a mixed-valence compound. For the formation of the orthorhombic crystal structure, Jahn-Teller distortions are assumed to play an important role. In this study, we aimed at the investigation of the crystal structure changes upon the substitution of Mn by the non-Jahn-Teller cation Fe3+. Therefore, we synthesized a series of YMn2-xFexO5 powder samples with x=0, 0.5, and 1 by a citrate technique. We utilized extended x-ray absorption fine structure (EXAFS) and x-ray absorption near-edge structure (XANES) analysis as well as density-functional theory (DFT) to investigate the two nonequivalent Wyckoff sites within the orthorhombic crystal structure (confirmed for all compositions) occupied by transition-metal atoms. For quantitative determination of structural short-range order, all plausible options of substitution of Fe for Mn are discussed. On the basis of these evaluations, the EXAFS and XANES behavior is analyzed and appropriate crystallographic weights are assigned to the subset of structural models in accordance with the experimental data. From EXAFS analysis, using multiple-scattering theory, we conclude only the 4h Wyckoff site to be occupied by Fe [occupancy refined is (100+/-3)% in case of x=1]. Furthermore, taking the XANES spectra into account, we are able to verify the EXAFS results and additionally explain the differences in the Mn K XANES spectra in dependence on x to be caused by changes in the dipole transitions to 4p final states. From quantitative pre-edge analysis an oxidation number of +4 for the Mn atom for x=1 is determined whereas the Fe valence is shown to be unchanged. Since the substitution process only involves one Wyckoff site, the experimentally observed limit to a maximum amount of x=1 is explained. Additionally, a possible disorder, discussed in the literature, is not proven for our samples. With DFT calculations, the experimental findings are verified on the basis of the total energy of the different possible electronic configurations. Crystal-field effects are identified to be responsible for the site-selective substitution of Fe for Mn.

Hazardous solid waste sent to landfill may contain heavy metals, posing risks to the environment and human health if leached out by rainwater or ground water. Antimony (Sb) is one of the contaminants of concern, and, similar to arsenic, many Sb compounds are toxic (in particular Sb(III)) Antimony may be found in mining waste streams, PET drink bottles, textiles and others (e.g., [1]) and is known to appear in conjunction with heavy metals such as As or Pb [2,3]. For regulators, such as the Environment Protection Authority Victoria, Australia, and for industry, the leachability and stability of Sb from wastes is of particular interest. The leachability of Sb depends on its chemical forms. Low leachability (high stability) is preferred, meaning that Sb is less likely to be released to the environment if exposed to rainfall or a rising groundwater table. While some studies have reported on the leachability of Sb [4], analyses of the chemical speciation of antimony are still rare [5,6], and insufficient information exists on the development of Sb species on the solid or liquid phases during leaching. This deficiency limits the ability to evaluate waste hazards and it affects regulators’ efforts to set realistic and safe Sb concentration limits for wastes sent to landfill. Therefore, more work is required on Sb speciation to improve waste management and, ultimately, minimise waste impact on the environment and human health.

Reactive hydride composites (RHCs) are very promising hydrogen storage materials for future applications due to their reduced reaction enthalpies and high gravimetric capacities. At present, the materials' functionality is limited by the reaction kinetics. A significant positive influence can be observed with addition of transition-metal-based additives. To understand the effect of these additives, the chemical state and changes during the reaction as well as the microstructural distribution were investigated using x-ray absorption near-edge structure (XANES) spectroscopy and anomalous small-angle x-ray scattering (ASAXS). In this work, zirconium- and vanadium-based additives were added to 2LiBH4-MgH2 composites and 2LiH-MgB2 composites and measured in the vicinity of the corresponding absorption edge. The measurements reveal the formation of finely distributed zirconium diboride and vanadium-based nanoparticles. The potential mechanisms for the observed influence on the reaction kinetics are discussed.

X-ray absorption fine structure (XAFS) studies of Ni nanograins embedded in carbonaceous films were performed basing on the K edge spectra of nickel. A series of samples containing various doses of Ni doped to the film during the deposition was studied. The crystalline structure and chemical constitution of formed nanograins were found dependent on the nickel dose. They change along the series from those similar to bulk structure of metallic Ni towards amorphous form of NiO. The Fourier transform fitting analysis based on Ni fcc and NiO rock salt models showed for all samples a significant reduction of the range of atomic order around Ni as compared to appropriate bulk materials. The changes in an oxide content rate in the nanograins were evaluated by fitting the coefficients of the linear combination spanned on two the most distinct measured XAFS spectra. We have found that low oxygen inflow resulted in formation of amorphous NiO, but saved the metallic core of grains. High oxygen uptake resulted in thorough grain oxidation.

We report on the bonding environment of In in InxAl1–xN (0.07 < x < 0.25) and InyGa1–yN (0.7 < y < 1) epilayers using extended X‐ray absorption fine structure (EXAFS) spectroscopy. The EXAFS analysis reveals that the In–N distance, in both the InAlN and the InGaN ternaries, is only weakly dependent on the In content. Contrary to that, the In–cation distances (in the 2nd nearest neighbour shell) have values closer to those predicted by Vegard's law. More specifically, the distribution of the In–cation distances is bimodal with the ff In–Ga and In–Al distances being smaller than the In–In distance. The variation of the In–Ga and In–Al distances with the In content is in agreement with Vegard's law while the In–In distance deviates from the expected values for In fractions smaller than 0.7. The identified composition‐dependent variation of the In–N and In–cation distances, indicates that the alloying induced stress in InAlN and InGaN is mainly accommodated by bond angle variation rather than bond length deformation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The short- and long-range order correlations of the crystal structure in the distorted perovskites La1−xSrxCoO3 and La1−xBaxCoO3 (0.0⩽x⩽0.5) have been studied by the neutron powder diffraction (NPD) and the Co K-edge X-ray absorption spectroscopy (XAS) measurements. The results of XAS and NPD indicate a local distortion around the Co3+ ions in LaCoO3 at room temperature. The substitution of the La3+ ions by the Sr2+(Ba2+) ions leads to a gradual increase of the Co–O–Co angle and is accompanied by an increase of the mean square relative displacement (MSRD) of the Co–O bond. These results correlate with an increase of the oxygen amplitude vibration in the direction perpendicular to the Co–O bond. The possible explanation of the observed changes of the crystal and electronic structures in the above-mentioned cobaltites is discussed.