SR XRD Research Articles

Correlation among crystal and local structure, phase transition, and Li–ion conduction of solid electrolyte Li7La3Zr2O12

The correlation among the crystal and local structure, phase transition, and Li–ion conduction of the solid electrolyte Li7La3Zr2O12 (LLZ) was investigated by quantum beam technique. According to the results of Rietveld refinement using Neutron diffraction data, the Li (8a) and Li (16f) sites have the deficiency of approximately 3∼5% in LLZ. These results of Li site occupancies were adopted to the Rietveld refinements with in situ Synchrotron X–ray Diffraction's (SR–XRD) from 300 K to 1000 K. The phase transition from the tetragonal to cubic phase was observed in in situ SR–XRD. The results of Rietveld refinements with in situ SR–XRD showed the coexistence of the tetragonal and cubic phase from 860 K to 880 K. The Li–ion conduction was discussed with respect to the atomic displacement parameters, electric density estimated by Rietveld refinements and Maximum Entropy Method (MEM) analysis, and local structure estimated by X–ray Absorption Spectra (XAS) and Pair Distribution Function (PDF) analysis. The Li–ion diffusion mechanism was discussed with crystal and local structures at high temperatures of LLZ. In particular, the coexistence of tetragonal phase at the phase transition, the bond of the Li and oxide at tetragonal phase, and the low symmetry of ZrO6 up to about 930 K are thought to inhibit Li diffusion.

Effect of Co and Sr substitution on the microwave dielectric properties of CaMg0.9Li0.2Si2O6-based ceramics for LTCC application

In this work, two low-temperature co-fired silicate ceramics (CaMg0.9-xLi0.2CoxSi2O6, x = 0.15–0.75, CMLCS; CaMg0.9-yLi0.2SrySi2O6, y = 0, 0.05, 0.1–0.5, CMLSS) were synthesized via solid-state reaction method with 0.5 wt%LBSCA glass addition. CMLCS and CMLSS were densely sintered at 925 °C, and had good chemical compatibility with silver. Optimal microwave dielectric properties (εr = 6.71, Q×f = 30124 GHz, and τf = −79.06 ppm/°C) and (εr = 6.78, Q×f = 32530 GHz, and τf = −52.99 ppm/°C) were obtained for CMLC0.15S and CMLS0.05S respectively. With increase in Co and Sr substitution, XRD and Raman spectra showed that second phases were produced, and densification process of CaMgSi2O6-based ceramics was promoted. Dielectric constant was influenced by relative density, Raman shift and second phase. The parameter Q×f was affected by the FWHM of Raman peaks as well as extrinsic factors that affected the temperature coefficient of resonant frequency. Therefore, the results suggested the potential of these two ceramics as candidates for LTCC application.

Effect of synthesis conditions on the structure and properties of new SiC x N y M z materials for spintronics

To produce novel thin-film spintronic materials based on a thermodynamic simulation, condensed phases with a complex composition are deposited in Si–С–N–H–M systems (M = Fe, Co, Ni) in a wide temperature range of 500-1300 K. As a result of the simulation CVD diagrams of Fe–Si–C–N–H(He), Co–Si–C–N–H(He), and Ni–Si–C–N–H(He) systems are obtained which enable the optimization of the synthesis process for film materials such as SiC x N y Fe z , SiC x N y Co z , and SiC x N y Ni z . SiC x N y Fe z films are experimentally deposited from a gas mixture containing ferrocene (C5H5)2Fe, organosilicon compound 1,1,1,3,3,3-hexamethyldisilazane HNSi2(CH3)6 (HMDS) under reduced pressure in the temperature range 1073-1273 K. The dependence of the physicochemical and functional properties of SiC x N y Fe z films on the synthesis conditions is found by a comples of modern research techniques such as IR and Raman spectroscopy, EDS, XPS, SEM, HREM, and synchrotron radiation powder XRD (SR XRD). By the Faraday method and electron paramagnetic resonance (EPR) the magnetic properties of the films are analyzed. It is shown that at a synthesis temperature of 1123 K the films are paramagnetic, and at a higher deposition temperature of 1273 K they are ferromagnetic.

Annealing effect on phase stability of doped zirconia using experimental and computational studies

The effects of annealing at 600°C and 800°C up to 2000h on the phase stabilities of doped stabilized zirconia, (Zr0.85Y0.15)O2−δ(8YSZ) and (Zr0.81Sc0.18Ce0.01)O2−δ(10SSZ), were investigated by Rietveld refinements with synchrotron X-ray diffraction (SR–XRD) and first-principle density functional theory (DFT) calculations. No marked change in the SR–XRD patterns was observed for the annealed samples of 8YSZ, and the amount of Y2O3 phases was less than 0.01mol% as estimated by comparison of the observed and simulated patterns in the annealed 8YSZ samples. Whereas the CeO2 phase was visible in the SR–XRD patterns of the annealed 10SSZ samples, the peaks of the mother doped zirconia host structure did not change, and other phases were not detected. The CeO2 content (under 0.12mol%) was estimated quantitatively from the Rietveld refinements. Furthermore, the phase separations from the doped zirconia to the oxides, viz., Y2O3,Sc2O3, and CeO2, were investigated by the molar solution energy (ΔEsol.) calculated using the DFT calculations. ΔEsol. for the phase separation to each oxide indicated that the CeO2 phase in 10SSZ would form more easily than the Y2O3 and Sc2O3 phases in 8YSZ and 10SSZ.

Supported palladium catalysts prepared by surface self-propagating thermal synthesis

Supported Pd/fiber glass, Pd/γ-Al2O3/fiber glass, Pd/γ-Al2O3 catalysts were prepared by Surface Self-propagating Thermal Synthesis (SSTS) and tested in selective hydrogenation of acetylene to ethylene in the presence of CO. Temperature change in local liquid-phase surrounding of Pd atoms was monitored by XAFS in situ by modeling the catalysts synthesis. The phase composition of samples at various synthesis stages was determined by XAFS spectroscopy and synchrotron X-ray diffraction (SR XRD). The type of support material and SSTS conditions were found to affect the catalytic activity of supported Pd catalysts. Thermal synthesis of Pd catalysts on the surface of supports was found to proceed via formation of the metallic phase followed by its transformation to oxide. The catalytic activity of thus prepared catalysts on fiber glass supports can expectedly be improved upon deposition of additional support (alumina) onto a fiber glass.

Non-isothermal kinetics and in situ SR XRD studies of hydrogen desorption from dihydrides of binary Ti–V alloys

Phase transformations during dynamic dehydrogenation of Ti1−xVxH2 (x = 0.1; 0.2; 0.3) were studied using in situ Synchrotron X-Ray Diffraction (SR XRD) and non-isothermal kinetics experiments. The main dehydrogenation path for γ-Ti1−xVxH2 was found to be γ → δ → β → βalloy. Body-centred tetragonal δ-hydride was found to be an intermediate phase of the γ → β transformation in Ti0.8–0.9V0.1–0.2H2. TDS, in situ SR XRD and isoconversional kinetics studies showed that hydrogen desorption from Ti1−xVxH2 is composed of simultaneous reactions taking place between 300 and 600 °C. The effective activation energy of hydrogen desorption depends on the vanadium contents and the reaction pathway, increasing from 21 kJ/mol H2 (γ → δ) to 60–110 kJ/mol H2 (δ → β).

Mass Spectrometric and Synchrotron Radiation based techniques for the identification and distribution of painting materials in samples from paints of Josep Maria Sert

BackgroundEstablishing the distribution of materials in paintings and that of their degradation products by imaging techniques is fundamental to understand the painting technique and can improve our knowledge on the conservation status of the painting. The combined use of chromatographic-mass spectrometric techniques, such as GC/MS or Py/GC/MS, and the chemical mapping of functional groups by imaging SR FTIR in transmission mode on thin sections and SR XRD line scans will be presented as a suitable approach to have a detailed characterisation of the materials in a paint sample, assuring their localisation in the sample build-up. This analytical approach has been used to study samples from Catalan paintings by Josep Maria Sert y Badía (20th century), a muralist achieving international recognition whose canvases adorned international buildings.ResultsThe pigments used by the painter as well as the organic materials used as binders and varnishes could be identified by means of conventional techniques. The distribution of these materials by means of Synchrotron Radiation based techniques allowed to establish the mixtures used by the painter depending on the purpose.ConclusionsResults show the suitability of the combined use of SR μFTIR and SR μXRD mapping and conventional techniques to unequivocally identify all the materials present in the sample and their localization in the sample build-up. This kind of approach becomes indispensable to solve the challenge of micro heterogeneous samples. The complementary interpretation of the data obtained with all the different techniques allowed the characterization of both organic and inorganic materials in the samples layer by layer as well as to establish the painting techniques used by Sert in the works-of-art under study.

Synchrotron diffraction studies and thermodynamics of hydrogen absorption–desorption processes in La 0.5Ce 0.5Ni 4Co

A hexagonal CaCu 5-type La 0.5Ce 0.5Ni 4Co intermetallic alloy was studied as H storage material in as cast condition using PCT and in situ Synchrotron XRD studies performed between 263 and 353 K. A significant shrinking of the unit cells takes place on a substitution of La with Ce. SR XRD showed the formation of two hexagonal hydrides, a γ-trihydride La 0.5Ce 0.5Ni 4CoH 3, and a saturated β-hexahydride La 0.5Ce 0.5Ni 4CoH ∼6. In addition, an α-H solid solution was experimentally observed. Hysteresis of hydrogen absorption and desorption between the flat single plateaus isotherms measured during the PCT measurements was rather small, with no indication of the formation of the thermodynamically stable γ-(La,Ce)(Ni,Co) 5H 3. The SR XRD revealed that (a) the relative abundance of the γ-hydride is higher during the desorption compared to the absorption; its relative amount reaches 50 wt.% in maximum; (b) anisotropic strains in all constituent phases during both hydrogen absorption and desorption are not developed; (c) the pressure of the formation of the γ-phase was found to be strongly temperature-dependent. The formation of large amounts of metastable γ-(La,Ce)(Ni,Co) 5H 3 hydride in quasiequilibrium experimental conditions applied during the SR XRD experiments and during reaching the thermodynamic equilibrium between the constituent phases can be responsible for the reduced hysteresis of the PCT isotherms and absence of noticeable anisotropic strains in the constituent phases.

Microstructural optimization of LaMg 12 alloy for hydrogen storage

A Rapid Solidification technique was applied to a LaMg 12 alloy in order to achieve refinement of the grain size. Thin ribbons were produced by solidifying the melt on a spinning copper wheel in an argon atmosphere using three different rotations speeds, 3.1, 10.5 and 20.9 m/s. The ribbons were analyzed by synchrotron X-ray diffraction (SR XRD), electron probe microanalysis (EPMA), and TEM, and they were subjected to hydrogen absorption–desorption cycling and to thermal desorption spectroscopy (TDS) characterization. SR XRD and EPMA revealed formation of two phases, LaMg 12− x and Mg. From SR XRD it was found that, depending on the cooling rate, the LaMg 12− x alloy crystallized with three different structural modifications, hexagonal TbCu 7 (highest cooling rate), tetragonal ThMn 12 (medium cooling rate) and orthorhombic LaMg 11 type (lowest cooling rate). A metastable TbCu 7-type structure (sp. gr. P6/mmm; a = 5.9617(3); c = 5.2153(5) Å) was not known from the earlier performed research and is reported for the La–Mg system for the first time. From the scanning electron microscopy (SEM) studies, RS was found to cause a significant grain refinement and an amorphisation for the highest cooling rate. The particle size of the formed hydride phases varied in the range 0.2–3 μm depending on the RS synthesis route used to prepare the original alloy. Hydrogen absorption resulted in a two-step disproportionation process: LaMg 12 + H 2 → LaH 3 + Mg → LaH 3 + MgH 2. A decrease in the grain size improved the hydrogenation kinetics. Hydrogen desorption studied by TDS and in situ SR XRD showed a major peak of hydrogen evolution at ∼370 °C. For the alloys synthesized at 10.5 m/s and 20.9 m/s, it was accompanied by an extra desorption event at 415 °C. This extra peak was associated with Mg-assisted low temperature hydrogen desorption from LaH 2 proceeding below 450 °C and leading to a recombination process to form the initial intermetallic alloy LaMg 12.

LaMg 11 with a giant unit cell synthesized by hydrogen metallurgy: Crystal structure and hydrogenation behavior

We have successfully applied a hydrogen metallurgy synthesis to yield LaMg 12− x intermetallic at 500 °C. During a vacuum thermal desorption from the LaH 3–MgH 2 nanocomposite prepared by reactive ball milling in H 2, hydrogen desorption from the La dihydride occurred via a mechanism of cooperative phase transformation at temperatures being 400° lower than the desorption from pure LaH 2. The crystal structure of the intermetallic was determined by synchrotron X-ray diffraction (SR XRD). The orthorhombic LaMg 12− x has a giant unit cell, the volume of which exceeds 8000 Å 3. In situ SR XRD studies showed the fine details of the hydrogen desorption process with several parallel and consecutive transformation steps.

Nanostructured Metal Hydrides for Hydrogen Storage Studied by In Situ Synchrotron and Neutron Diffraction

AbstractThis work was focused on studies of the metal hydride materials having a potential in building hydrogen storage systems with high gravimetric and volumetric efficiencies of H storage and formed / decomposed with high rates of hydrogen exchange. In situ diffraction studies of the metal-hydrogen systems were explored as a valuable tool in probing both the mechanism of the phase-structural transformations and their kinetics. Two complementary techniques, namely Neutron Powder Diffraction (NPD) and Synchrotron X-ray diffraction (SR XRD) were utilised. High pressure in situ NPD studies were performed at D2 pressures reaching 1000 bar at the D1B diffractometer accommodated at Institute Laue Langevin, Grenoble. The data of the time resolved in situ SR XRD were collected at the Swiss Norwegian Beam Lines, ESRF, Grenoble in the pressure range up to 50 bar H2 at temperatures 20-400°C.The systems studied by NPD at high pressures included deuterated Al-modified Laves-type C15 ZrFe2-xAlx intermetallics with x = 0.02; 0.04 and 0.20 and the CeNi5-D2 system. D content, hysteresis of H uptake and release, unit cell expansion and stability of the hydrides systematically change with Al content.Deuteration exhibited a very fast kinetics; it resulted in increase of the unit cells volumes reaching 23.5 % for ZrFe1.98Al0.02D2.9(1) and associated with exclusive occupancy of the Zr2(Fe,Al)2 tetrahedra.For CeNi5 deuteration yielded a hexahydride CeNi5D6.2 (20°C, 776 bar D2) and was accompanied by a nearly isotropic volume expansion reaching 30.1% (∆a/a=10.0%; ∆c/c=7.5%). Deuterium atoms fill three different interstitial sites including Ce2Ni2, Ce2Ni3 and Ni4. Significant hysteresis was observed on the first absorption-desorption cycle. This hysteresis decreased on the absorption-desorption cycling.A different approach to the development of H storage systems is based on the hydrides of light elements, first of all the Mg-based ones. These systems were studied by SR XRD. Reactive ball milling in hydrogen (HRBM) allowed synthesis of the nanostructured Mg-based hydrides.The experimental parameters (PH2, T, energy of milling, ball / sample ratio and balls size), significantly influence rate of hydrogenation. The studies confirmed (a) a completeness of hydrogenation of Mg into MgH2; (b) indicated a partial transformation of the originally formed -MgH2 into a metastable -MgH2 (a ratio / was 3/1); (c) yielded the crystallite size for the main hydrogenation product, -MgH2, as close to 10 nm. Influence of the additives to Mg on the structure and hydrogen absorption/desorption properties and cycle behaviour of the composites was established and will be discussed in the paper.

Analytical study of the behaviour of some ingredients used in lustre ceramic decorations following different recipes

Ceramic lustre is a fine decoration obtained by a complex technical process. Although the general production technique is more or less known, it is much more difficult to specify the ingredients mixed in the ancient recipes used to produce lustre and their function during the process, especially components as mercury sulphide and iron oxide. To understand this point, mixtures of the components were previously characterised and tested to see which mixtures resulted in the desired lustre. Synchrotron-Radiation-Source X-ray Diffraction (SRS–XRD) of the fired mixtures was performed to check the changes produced in the ingredients. Also Voltammetry of immobilised Microparticles was applied to the raw pigment powders to obtain information about the redox behaviour. Square-wave voltammetry demonstrates the possibility of different deposits that can be formed in the first steps of the reduction process in the pigment mixture for lustre production, especially those related to solid-form reactions and pigment-electrolyte interactions. Moreover, SR–XRD shows the formation of different crystalline phases at the end of the process, in this case probably also related to gas–solid interactions and to a strong reduction atmosphere.

INSIGHTS INTO NORTH MESOPOTAMIAN ‘METALLIC WARE’*

With the aim of shedding new light on the still poorly understood North Mesopotamian metallic ware, ceramic and soil samples from Tell Beydar (northeastern Syria, third millennium bc) were investigated using a range of analytical techniques, including optical microscopy, SR–XRD and SEM–EDX. The objective of this work was to differentiate calcareous metallic ware from non‐calcareous ware without the aid of chemical analyses and to find further validation of the existing hypothesis that the former group is an imitation of the latter. A third group of metallic wares from Tell Beydar is believed to be of non‐local, still regional origin.

Neutron and X-ray characterisation of the metallurgical properties of a 7th century BC Corinthian-type bronze helmet

Neutron and synchrotron X-ray diffraction, X-ray fluorescence and FTIR were used to examine a Corinthian-type bronze helmet which is now on display at The Manchester Museum, UK. This type of helmet was manufactured out of a single piece of bronze, probably on a rod-anvil, and like all body-armour it was made to measure. Neutron diffraction sampling of the bronze volume in different areas was used to study the composition, microstructure and crystallographic texture of the alloy in order to draw conclusions about the manufacturing processes. The neutron data revealed the presence of microstrains and non-random distributions of bronze grains hinting at annealing-hammering working cycles in order to harden and shape the alloy. X-ray fluorescence showed that the main body of the helmet is a copper–tin alloy, while the noseguard contains zinc in high abundance. This key compositional difference confirms that the noseguard is not the original but is a modern substitute fabricated for restoration purposes. SR XRD and FTIR from several spots on the head and noseguard identified several surface corrosion products and showed a variation of the Cu–Sn or Cu–Zn percentage compositions, and of the mineral phases. Small samples of corrosion flakes extracted from the outside and inside of the helmet were used to obtain powder XRD patterns.

Elastic Behaviour of Thin Stabilized-Zirconia Coatings

The residual stress in thin coatings of yttria stabilised-zirconia produced by Low Pressure Plasma Spraying were measured by X-ray Diffraction, using laboratory as well as synchrotron radiation sources. The specific microstructure, with absence of texture and fine distribution of nearly equiaxed grains, point out that despite the markedly anisotropic nature of cubic zirconia, coatings can be considered as macroscopically isotropic. This picture is also confirmed by the results of a parallel study, where the X-ray elastic constants were measured in-situ along two crystallographic directions ([440] and [620]): measured values agree fairly well with those calculated from single-crystal data under the Neerfeld-Hill assumptions. SR XRD provided a detailed information on the stress field across the thickness of the zirconia coatings. In particular the presence of a stress gradient was observed and modelled. The average stress is compressive, and increases with the coating thickness. Compression tend to increase from the surface toward the inside of the coating reaching a maximum of ~-1.0 GPa in a 24 µm coating.

Phase stability of scandia–yttria-stabilized zirconia TBCs

Abstract The evolution in phase composition resulting from 1400°C ageing of ZrO 2 samples stabilized by ∼4–7 mol.% each of Y 2 O 3 (YSZ), Sc 2 O 3 (ScSZ), or a mixture of Sc 2 O 3 –Y 2 O 3 (SYSZ) was studied by synchrotron radiation X-ray diffraction (SR XRD) using whole powder pattern fitting (WPPF), a recently proposed Rietveld-based method for the simultaneous refinement of phase composition and crystal microstructure. The results suggest that SYSZ has better high temperature tetragonal phase stability than the current state-of-art YSZ. For example, a plasma-sprayed coating of SYSZ (6.57 mol.%Sc 2 O 3 –1.00 mol.%Y 2 O 3 ) remained 96.7% in its original tetragonal phase (presumably t′, c / a of 1.0058) after being aged 100 h at 1400°C and then 24 h at 1480°C, whereas a 4.5 mol.% YSZ coating was transformed into two new tetragonal phases, one a low-stabilizer phase with c / a of 1.0154 (44.8%) and the other a high-stabilizer zirconia phase with c / a of 1.003 (46.5%), with some monoclinic (8.7%) formed. The phase compositions found for the various powder and coating specimens, together with information regarding lattice parameters, crystalline domain size and microstrain, also obtained by WPPF, are discussed in terms of the high-temperature phase stability of the YSZ vs SYSZ systems.