Wavelength Dispersive X-ray Spectrometer Research Articles

Development of a Polychromatic Simultaneous Wavelength Dispersive X-ray Spectrometer and Improvement in Its Precision: From Principle Verification to Chemical State Analysis of Cathode Materials in Lithium-Ion Batteries

リチウムイオン電池（Lithium-ion Battery, LIB）や磁性体といった高機能材料の開発において，材料の劣化観察や高機能発現機構の解明のため，元素の状態変化をとらえる分析が行われている．試料準備の容易な蛍光X線分析も化学状態分析に応用できることが知られているが，産業界への応用は途上にある．著者らは産業界での状態分析を想定した波長分散型蛍光X線分析装置を開発してきた．本論文では，開発装置の原理説明からLIB用正極活物質の状態変化をとらえた事例を紹介する．装置原理の説明に加え，これまで開発した二つの装置の比較やほかの波長分散型蛍光X線分析装置との違いについて言及する．加えて，標準物質の測定例及びLIB用正極活物質の状態変化をとらえた三つの事例を挙げる．これらの結果より，開発した波長分散型蛍光X線分析装置が各活物質の充放電過程における遷移元素成分の状態変化を適切に捕捉できることを確認した．

New experimental studies on the phase relationship of the Bi–Pb–Te system

Knowledge of the phase relationships is crucial in developing thermoelectric materials and allows a better understanding of the properties of the relevant systems. In the present work, we present the liquidus projection of the Bi-Pb-Te system and phase equilibria of the BiTe-PbTe-Bi2Te3 portion at 400 and 520 °C. Alloys were prepared by melting high-purity elements in cleaned quartz tubes and their microstructures were characterized by scanning electron microscopy, electron probe microanalysis, wavelength-dispersive X-ray spectrometer, X-ray diffractometry and differential scanning calorimetry. The binary compound BiTe extends up to 16.7 at.% Pb along BiTe-PbTe at 520 °C. The solubilities of Bi in PbTe were established to be 3.6, 3.8 and 10.8 at.% at 360, 400 and 520 °C, respectively. This work will help to understand the microstructure evolution during preparation and service and promote the designing of the Bi–Pb–Te-based high-performance materials.

Characterization of the chemical shift and asymmetry indices of praseodium, neodymium, samarium, gadolinium, and terbium compounds by wavelength dispersive X-ray fluorescence (WDXRF)

Emitted X-ray energies, line shapes, fluorescence yields, absorption probabilities and absorption edges of the elements are X-ray fundamental parameters that are of practical significance because they facilitate compositional analysis of complex materials. They are also a potent test of atomic theory. The chemical effects may cause changes in the energy of the X-ray lines and line shapes, such as the full width at half maximum and asymmetry index values depending on the chemical state of the substance. Although these effects vary for each element, the causes of these differences have been investigated. In this study, changes in chemical action values of lanthanide group compounds were investigated using a single crystal wavelength dispersive X-ray spectrometer equipped with a rhodium anode X-ray tube. The Ll and Lη X-ray emission lines are characterized by fitting of the Lorentz function. The chemical shift was investigated according to the chemical bond type, molecular structure, and oxidation number.

Traceable Characterization of Nanomaterials by X-ray Spectrometry Using Calibrated Instrumentation.

Traceable characterization methods allow for the accurate correlation of the functionality or toxicity of nanomaterials with their underlaying chemical, structural or physical material properties. These correlations are required for the directed development of nanomaterials to reach target functionalities such as conversion efficiencies or selective sensitivities. The reliable characterization of nanomaterials requires techniques that often need to be adapted to the nano-scaled dimensions of the samples with respect to both the spatial dimensions of the probe and the instrumental or experimental discrimination capability. The traceability of analytical methods revealing information on chemical material properties relies on reference materials or qualified calibration samples, the spatial elemental distributions of which must be very similar to the nanomaterial of interest. At the nanoscale, however, only few well-known reference materials exist. An alternate route to establish the required traceability lays in the physical calibration of the analytical instrument’s response behavior and efficiency in conjunction with a good knowledge of the various interaction probabilities. For the elemental analysis, speciation, and coordination of nanomaterials, such a physical traceability can be achieved with X-ray spectrometry. This requires the radiometric calibration of energy- and wavelength-dispersive X-ray spectrometers, as well as the reliable determination of atomic X-ray fundamental parameters using such instrumentation. In different operational configurations, the information depths, discrimination capability, and sensitivity of X-ray spectrometry can be considerably modified while preserving its traceability, allowing for the characterization of surface contamination as well as interfacial thin layer and nanoparticle chemical compositions. Furthermore, time-resolved and hybrid approaches provide access to analytical information under operando conditions or reveal dimensional information, such as elemental or species depth profiles of nanomaterials. The aim of this review is to demonstrate the absolute quantification capabilities of SI-traceable X-ray spectrometry based upon calibrated instrumentation and knowledge about X-ray interaction probabilities.

SI traceable characterisation of nanomaterials by X-ray spectrometry

The development of new materials and the assessment of nanomaterials require the correlation of the materials’ functionality or toxicity with their chemical and physical properties. To probe these properties, analytical methods that are both sensitive and selective at the nano-and microscales are required. The reliability of most analytical methods is based on the availability of reference materials or calibration samples, the spatial elemental compositions of which have to be as similar as possible to the matrix of the specimens of interest. However, there is a drastic lack of reference materials in particular at the nanoscale. Physikalisch-Technische Bundesanstalt (PTB) addresses this challenge by means of a bottom-up X-ray analytical method where all instrumental and experimental parameters are determined with known contributions to the uncertainty of the analytical results. This first-principle (FP) based approach does not require any reference materials but a complete characterisation of the analytical instruments’ characteristics and, in addition, knowledge on the X-ray fundamental parameters related to the elements composing the sample. In order to reveal more reliable FP data in line with recent FP roadmap recommendations, PTB has been developing and using calibrated instrumentation, both energy- and wavelength-dispersive X-ray spectrometers, in conjunction with well-known synchrotron radiation (SR) of high spectral purity. Examples of recent PTB works on different FP determinations mostly of technologically relevant elements are given. SR based X-ray spectrometric methods allow for the variation of the analytical sensitivity, selectivity, and information depth needed to effectively reveal the spatial, elemental, and chemical specimen parameters of interest. Examples of particle characterisation, interfacial speciation, elemental depth profiling, as well as layer composition and thickness characterisations in advanced materials and nanostructures as well as for in-situ conditions are given.

Study on Flotability and Surface Oxidation of Sulfide Minerals from the Tailing of an Iron-Copper Mine Using Electron Probe Microanalyzer

ABSTRACT With the depletion of high-grade ores, beneficiation of valuable minerals from mineral processing tailings attracts attentions of mining companies and researchers. Recovery of valuable sulfide minerals by flotation from the tailing of an iron-copper mine in central China was investigated in this paper. The surface oxidation status of sulfide minerals is an important factor influencing their flotation properties. Electron probe microanalyzer (EPMA) equipped with wavelength dispersive X-ray spectrometer (WDS) is an effective apparatus for characterizing solid surface (interface), which can analyze the composition and element distribution on the surfaces of sulfide minerals so as to understand their oxidation status. EPMA-WDS was employed to analyze the phenomenon responsible for the low flotation recovery of chalcopyrite and pyrite in this tailing. The research methodology is a useful reference for further work in the field of sulfide mineral surface analysis.

Thermal stability and flame retardant properties of calcium- and magnesium-hypophosphite-finished cotton fabrics and the evaluation of interaction with clay and POSS nanoparticles

The aim of this study was to investigate the effect of calcium hypophosphite (CaHP) and magnesium hypophosphite (MgHP) on the thermal stability and fire retardant properties of cotton fabrics. The effects of water-soluble nanoparticles, namely Na-montmorillonite and octaammonium polyhedral oligomeric silsesquioxane (OA-POSS), in the presence of CaHP were also investigated. The characterizations of flame-retardant-treated cotton fabrics were performed using thermogravimetric analysis, limiting oxygen index (LOI) and mass loss calorimeter studies. The residues remained after mass loss calorimeter test were characterized by conducting attenuated total reflectance Fourier-transform infrared spectroscopy and scanning electron microscopy with a wavelength-dispersive X-ray spectrometer. The results showed that the fire performance of cotton fabric increased as the treated amount of both hypophosphite compounds increased. CaHP showed better fire performance than MgHP. The fire retardant performance of CaHP was further improved when used with nanoparticles. The highest LOI value of 24.2 and the lowest peak heat release rate (PHRR) of 43 ± 3 kW m−2 were achieved with the use of CaHP and OA-POSS at a ratio of 19:1.

You Do What in Your Microprobe?! The EPMA as a Multimode Platform for Nitride Semiconductor Characterization

While the use of electron probe microanalysis (EPMA) is widespread in the geological and metallurgical sciences, it remains less prevalent in the field of semiconductor research. For these materials, trace element (i.e. dopant) levels typically lie near or beneath the detection limit of wavelength-dispersive Xray (WDX) spectrometers, while alloy compositions of ternary mixtures and multilayer structures can more readily be determined using X-ray diffraction techniques. The electron beam measurements more commonly applied to semiconductors remain transmission electron microscopy (for structural characterization), and scanning electron microscopy (topographic, optical and electrical information). Despite this, there are many aspects of the EPMA that make it an attractive platform for all of thesetypes of semiconductor characterization, particularly when combining compositional information fromWDX with complementary and simultaneously-acquired signals. These advantages include: built-inlight optics; a stable, quantified and high-current beam; and a combined large-area and high-resolutionmapping capability. This allows the measurement of cathodoluminescence (CL), electron beam-inducedcurrent (EBIC) and electron channelling contrast imaging (ECCI) signals alongside WDX, which weapply to the investigation of visible and UV AlxInyGa1-x-yN materials, devices and nanostructures.

Study of detection limit and sensitivity of Kα and Lα spectral lines of 47Ag, 48Cd, and 50Sn elements using polychromatic wavelength dispersive X‐ray spectrometer

The purpose of this work was to evaluate the instrumental detection limit and sensitivity for determination of elemental composition of 47Ag, 48Cd, and 50Sn elements in the standard liquid solution with highly advanced polychromatic wavelength dispersive X‐ray fluorescence (PC‐WDXRF) spectrometer equipped with 45Rh X‐ray tube. To improve the sensitivity and detection limit, the bremsstrahlung coming from 45Rh source were reduced by choosing suitable primary beam filters (Al and Cu). Instrumental measuring parameters as well as study of linear calibration curves of K and L shell spectral lines were evaluated to select the best conditions for 47Ag, 48Cd, and 50Sn quantification. The detection limit of Lα spectral lines were found to be ~3 to 5 times lower than Kα spectral lines which results in high sensitivity.

A new life for the wavelength-dispersive X-ray spectrometer (WDS): incorporation of a silicon drift detector into the WDS for improved quantification and X-ray mapping

The wavelength-dispersive X-ray spectrometer (WDS) has been around for a long time and the design has not changed much since its original development. The electron microprobe operator using WDS has to be meticulous in monitoring items such as gas flow, gas purity, gas pressure, noise levels of baseline and window, gas flow proportional counter (GFPC) voltage levels, count rate suppression, anode wire contamination and other detector parameters.Recent development and improvements of silicon drift detectors (SDD’s) has allowed the incorporation of a SDD as the X-ray detector in place of the proportional counter (PC) and/or gas flow proportional counter (GFPC). This allows minimal mechanical alteration and no loss of movement range.The superiority of a WDS with a SDD, referred to as SD-WDS, is easily seen once in operation. The SD-WDS removes many artefacts including the worse of all high order diffraction, thus allowing more accurate analysis. The incorporation of the SDD has been found to improve the light and mid element range and consequently improving the detection limit for these elements. It is also possible to obtain much more reliable results at high count rates with almost no change in resolution, gain and zero-peak characteristics of the energy spectrum.

Benefits from bremsstrahlung distribution evaluation to get unknown information from specimen in SEM and TEM

The energy-dispersive X-ray spectrometer (EDS or EDX) is a commonly used device to characterise the composition of investigated material in scanning and transmission electron microscopes (SEM and TEM). One major benefit compared to wavelength-dispersive X-ray spectrometers (WDS) is that EDS systems collect the entire spectrum simultaneously. Therefore, not only are all emitted characteristic X-ray lines in the spectrum, but also the complete bremsstrahlung distribution is included. It is possible to get information about the specimen even from this radiation, which is usually perceived more as a disturbing background. This is possible by using theoretical model knowledge about bremsstrahlung excitation and absorption in the specimen in comparison to the actual measured spectrum. The core aim of this investigation is to present a method for better bremsstrahlung fitting in unknown geometry cases by variation of the geometry parameters and to utilise this knowledge also for characteristic radiation evaluation. A method is described, which allows the parameterisation of the true X-ray absorption conditions during spectrum acquisition. An ‘effective tilt’ angle parameter is determined by evaluation of the bremsstrahlung shape of the measured SEM spectra. It is useful for bremsstrahlung background approximation, with exact calculations of the absorption edges below the characteristic peaks, required for P/B-ZAF model based quantification methods. It can even be used for ZAF based quantification models as a variable input parameter. The analytical results are then much more reliable for the different absorption effects from irregular specimen surfaces because the unknown absorption dependency is considered. Finally, the method is also applied for evaluation of TEM spectra. In this case, the real physical parameter optimisation is with sample thickness (mass thickness), which is influencing the emitted and measured spectrum due to different absorption with TEM measurements. The effects are in the very low energy part of the spectrum, and are much more visible with most recent windowless TEM detectors. The thickness of the sample can be determined in this way from the measured bremsstrahlung spectrum shape.

Effects of silica addition on chromium distribution in stainless-steel slag

ABSTRACTThe present study was aimed at highlighting the effect of silica on chromium distribution and enrichment in certain stainless-steel slag when basicity ranged from 0.96 to 1.96. Industrial slag samples of the CaO–Al2O3–MgO–SiO2–CrOX–FeXO system were investigated with different silica addition contents and soaked at the targeted regime. X-ray diffraction, electron probe micro-analyzer with wavelength-dispersive X-ray spectrometer, as well as Fourier-transform infrared spectroscopy and NIH ImageJ software were used for sample characterisation. FactSage version 6.4 was employed to calculate phase equilibria at 1200°C for the slag system to understand the crystallisation procedure. Results indicated that chromium was enriched in CaCr2O4 at high basicity, but in spinel at lower basicity. The spinel phase increased in size and chromium distribution with Fe(II) participated in growth with the decrease in depolymerisation of the slag structure.

High resolution K X-ray spectra of selected silicates induced by MeV proton and carbon micro-beams

Abstract Recently we developed a high resolution wavelength dispersive X-ray spectrometer based on the flat diffraction crystals for use with focused ion beams and used it to study chemical effects in ion beam induced Si K X-ray spectra of silicon and its selected binary compounds. In this work we extended the study to selected silicates. We measured high resolution Si Kα and Kβ X-ray spectra of three silicates: feldspar, kyanite and tourmaline. The spectra have been measured with 2 MeV protons (Kα and Kβ regions) and 20 MeV carbon ions (only Kα region). The results obtained for peak relative intensities were analysed and compared with the related relative intensities obtained from Si, SiC and SiO2.

Mg/Ca and Sr/Ca as novel geochemical proxies for understanding sediment transport processes within coral reefs

Sediment transport is a key driver of reef zonation and biodiversity, where an understanding of sediment dynamics gives insights into past reef processes and allows the prediction of geomorphic responses to changing environmental conditions. However, modal conditions within the back-reef seldom promote sediment transport, hence direct observation is inherently difficult. Large benthic foraminifera (LBF) have previously been employed as ‘tracers’ to infer sediment transport pathways on coral reefs, as their habitat is largely restricted to the algal flat and post-mortem, their calcium carbonate test is susceptible to sediment transport forces into the back-reef. Foraminiferal test abundance and post-depositional test alteration have been used as proxies for sediment transport, although the resolution of these measures becomes limited by low test abundance and the lack of variation within test alteration. Here we propose the novel use of elemental ratios as a proxy for sediment transport. Two species, Baculogypsina sphaerulata and Calcarina capricornia, were analysed using a taphonomic index within One Tree and Lady Musgrave reefs, Great Barrier Reef (Australia). Inductively coupled plasma-atomic emission spectrometry (ICP-AES) was used to determine Mg/Ca and Sr/Ca and these ratios were compared with taphonomic data. Decreases in test Mg/Ca accompany increases in Sr/Ca in specimens from algal-flat to lagoonal samples in both species, mirroring trends indicated by taphonomic values, therefore indicating a relationship with test alteration. To delineate mechanisms driving changes in elemental ratios, back-scattered electron (BSE) images, elemental mapping and in situ quantitative spot analyses by electron microprobe microanalysis (EPMA) using wavelength dispersive X-ray spectrometers (WDS) were performed on un-altered algal flat and heavily abraded tests for both species. EPMA analyses reveal heterogeneity in Mg/Ca between spines and the test wall, implying the loss of appendages results in a decrease in Mg/Ca. BSE imaging and WDS elemental mapping provided evidence for cementation, facilitated by microbial-boring as the primary cause of increasing Sr/Ca. These novel proxies hold advantages over taphonomic measures and further provide a rapid method to infer sediment transport pathways within back-reef environments.

Development of an energy‐dispersive X‐ray spectroscopy analyzer employing superconducting tunnel junction array detectors toward nanometer‐scale elemental mapping

Energy‐dispersive X‐ray detectors based on superconducting tunnel junctions (STJs) exhibit at best energy resolution of about 5 eV in full width at half‐maximum for soft X‐rays with energy levels of less than ~1 keV as well as a large sensitive area (>1 mm2) and a high counting rate capability (>500 kcps). We have developed an energy‐dispersive X‐ray spectroscopy analyzer combined with a scanning electron microscope and STJs to realize elemental mapping with high energy‐resolving power. To improve the collection efficiency of the fluorescence X‐rays, a polycapillary collimating X‐ray lens was installed in the analyzer. The overall system efficiency of the analyzer was more than 1 × 10−4 sr in the soft X‐ray range. Its counting rate performance for the N‐Kα line was 9.4 cps/nA, near that of setups comprising an electron probe microanalyzer and wavelength‐dispersive X‐ray spectrometers (WDSs). By improving the X‐ray optics, the counting rate is expected to be increased more than 600‐fold. The energy resolution of the developed analyzer was assessed according to the full width at half‐maximum of the N‐Kα peak, which was measured to be 10 eV, indicating an energy resolution about 7 times better than that of conventional X‐ray spectroscopy analyzers employing silicon drift detectors (SDDs). These results indicate that the improved analyzer employing STJs can realize both the high throughputs of SDDs and the high energy resolution of WDSs. Copyright © 2017 John Wiley & Sons, Ltd.

Characterization of the interfaces formed at the silicon nitride superalloy joints

In this study, silicon nitride ceramics (Si3N4) were joined by using a capacitor discharge technique with an Inconel 718 superalloy interlayer and heat-treated in order to determine possible reactions between these two materials. After capacitor discharge joining, some of the samples were heat-treated at 1100 °C under air and the resulting interfacial microstructure was characterized by using a scanning electron microscope (SEM) attached with an energy-dispersive x-ray spectrometer (EDS) and wavelength dispersive x-ray spectrometer (WDS). According to back-scattered electron images (BSE), all the joining samples were well bonded through the interlayer and cracks were not observed along the interlayer, interface and the ceramics. According to point SEM–EDS and SEM–WDS analysis, the reaction layer and nitrogen (N) were not detected but a small amount of silicon (Si) and aluminium (Al) was detected at the interlayer of as-joined samples. For the heat-treated samples at 1100 °C, the symmetrical reaction layer was observed at both sides of the interlayer which is expanding towards the ceramic side and approximately 25-nm-thick another continuous reaction layer next to this was also determined. According to SEM–EDS and SEM–WDS point-line scan analysis along the metallic interface and ceramic side, nickel (Ni), iron (Fe) and chromium (Cr) were detected at the reaction layer next to the ceramic side, whereas mainly Cr, niobium (Nb), molybdenum (Mo), titanium (Ti) and Al were concentrated at the 25-nm-thick reaction layer.

Study of ion beam induced chemical effects in silicon with a downsized high resolution X-ray spectrometer for use with focused ion beams

A downsized wavelength dispersive X-ray spectrometer, employing a flat crystal and a CCD detector for use with focused ion beams has been constructed and employed to study ion beam induced chemical effects in Si K X-ray spectra from silicon and its selected compounds.

Wavelength dispersive μPIXE setup for the ion microprobe

We have developed a small wavelength dispersive X-ray spectrometer to explore the possibility of performing chemical speciation on microscopic samples utilizing focused ion beams available at the Rudjer Boskovic Institute ion microprobe. Although PIXE spectra are in principle chemically invariant, small influence of chemical effects could be observed even with Si(Li) or SDD detectors. Such chemical effects can be clearly seen with high resolution crystal X-ray spectrometers having energy resolution of several eV. A dedicated vacuum chamber, housing the diffraction crystal, sample holder and CCD X-ray detector, was constructed and positioned behind the main ion microprobe vacuum chamber. Here we will briefly describe the spectrometer, and illustrate its capabilities on measured K X-ray spectra of selected sulfur compounds. We will also demonstrate its abilities to resolve K and M X-ray lines irresolvable by solid state ED detectors usually used in PIXE.

Effect of Chromium Vapor Pressure on Accelerated Poisoning Tests for (La0.6Sr0.4)(Co0.2Fe0.8)O3 Cathode

One of the most critical issues causing degradation of SOFCs is poisoning of cathodes by a trace amount of impurities transferred with air such as sulfur (S) and chromium (Cr), and therefore, we are continuously investigating the test method on accelerated degradation by these impurities. In our previous studies on Cr poisoning, chromium metal covered with Cr2O3 was directly placed on the current collector of the cathode as a source of Cr vapor. However, the setting accelerated the performance degradation in surplus. In order to perform accerelated poisoning test at an appropriate rate, we improved the cell operating equipment to control the Cr vapor pressure during the cell tests. The Cr vapor pressure was controlled by adjusting the place and temperature of the Cr source. The cell tests were operated at 1073 K under controlled feeding rate of Cr vapor after the cell performance became stable. The degradation behavior was analyzed with AC impedance analysis, field emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray analysis (EDX) / wavelength-dispersive X-ray spectrometer (WDS). The vapor pressure of Cr species was estimated from the amount of Cr trapped by (Sm,Sr)CoO3cathode in the same equipment of cell tests. The degradation rate decreased with decreasing the Cr vapor pressure, and the amount of Cr species deposited in LSCF cathode decreased with decreasing the Cr vapor pressure.

High-resolution X-ray emission spectroscopy with transition-edge sensors: present performance and future potential.

X-ray emission spectroscopy (XES) is a powerful element-selective tool to analyze the oxidation states of atoms in complex compounds, determine their electronic configuration, and identify unknown compounds in challenging environments. Until now the low efficiency of wavelength-dispersive X-ray spectrometer technology has limited the use of XES, especially in combination with weaker laboratory X-ray sources. More efficient energy-dispersive detectors have either insufficient energy resolution because of the statistical limits described by Fano or too low counting rates to be of practical use. This paper updates an approach to high-resolution X-ray emission spectroscopy that uses a microcalorimeter detector array of superconducting transition-edge sensors (TESs). TES arrays are discussed and compared with conventional methods, and shown under which circumstances they are superior. It is also shown that a TES array can be integrated into a table-top time-resolved X-ray source and a soft X-ray synchrotron beamline to perform emission spectroscopy with good chemical sensitivity over a very wide range of energies.