Synchrotron X-ray Powder Diffraction Study Research Articles

Tuning of thermoelectric performance by modulating vibrational properties in Ni-doped Sb2Te3

Sb2Te3, a binary chalcogenide-based 3D topological insulator, attracts significant attention for its exceptional thermoelectric performance. We report the vibrational properties of magnetically doped Sb2Te3 thermoelectric material. Ni doping induces defect/disorder in the system and plays a positive role in engineering the thermoelectric properties through tuning the vibrational phonon modes. Synchrotron powder x-ray diffraction study confirms good crystalline quality and single-phase nature of the synthesized samples. The change in structural parameters, including B iso and strain, further corroborate with structural disorder. Detailed modification of phonon modes with doping and temperature variation is analysed from temperature-dependent Raman spectroscopic measurement. Compressive lattice strain is observed from the blue shift of Raman peaks owing to Ni incorporation in Sb site. An attempt is made to extract the lattice thermal conductivity from total thermal conductivity estimated through optothermal Raman studies. Hall concentration data support the change in temperature-dependent resistivity and thermopower. Remarkable increase in thermopower is observed after Ni doping. Simulation of the Pisarenko model, indicating the convergence of the valence band, explains the observed enhancement of thermopower in Sb2−x Ni x Te3. The energy gap between the light and heavy valence band at Γ point is found to be 30 meV (for Sb2Te3), which is reduced to 3 meV (in Sb1.98Ni0.02Te3). A significant increase in thermoelectric power factor is obtained from 715 μWm−1K−2 for pristine Sb2Te3 to 2415 μWm−1K−2 for Ni-doped Sb2Te3 sample. Finally, the thermoelectric figure of merit, ZT is found to increase by four times in Sb1.98Ni0.02Te3 than that of its pristine counterpart.

Unraveling Effects of Current Density and Silicon on Silicon-Graphite Composite Anodes By in-Situ Synchrotron X-Ray Diffraction

The development of lithium-ion batteries (LIBs) with high capacity and rate capabilities is imperative to meet energy demands for both transport and grid storage in the future. Due to its relative abundance and excellent cycling stability, state of the art LIBs contains graphite as the main anode component. However, graphite suffers from a low theoretical specific capacity of 372 mAhg-1 [ 1 ]. Alternatively, silicon (Si) has emerged as a promising energy-dense anode material with a theoretical specific capacity 10 times higher than graphite, but their widespread application is impeded by low electrical conductivity and extremely poor cycling stability due to large volume variations when alloying with lithium during electrochemical cycling [ 2 ]. Interestingly, silicon-graphite (SiG) composites have been pinpointed as promising options for producing improved anodes, which aims to combine graphite’s high electronic conductivity and structural stability with silicon’s high specific capacity. As expected, increasing the silicon content of SiG anodes reduces the cycling stability [3]. Optimization of SiG with respect to silicon content and utilization of silicon is not straightforward, and a comprehensive analysis on the effect of variations of silicon content and current density on SiG andoes is key. To investigate these interactions, in-situ synchrotron X-ray diffraction (XRD) analysis of composite anodes with varying silicon content at increasing c-rates was performed.In situ experiments were performed at BM01 of the European Synchrotron Radiation Facility (ESRF). An in-situ electrochemical cell consisting of two current collectors, in which the lower current collector is made of brass and the upper current collector is made of stainless steel, was utilized [ 4 ]. A half-cell was then assembled between the two current collectors in a coin cell configuration using lithium metal as the counter electrode and a glass fiber separator. 1M LIFSI in 1:1 vol EC: DMC was used as the liquid electrolyte. The current collectors each have a thin single crystal sapphire window that is mostly transparent to X-ray but have distinct signals that can be masked out in post-processing. To avoid diffraction signal from the underlying copper current collector of the electrode, the composite anode consists of electrodes cast on copper foil as well as a free-standing section. The assembled cell was galvanostatically cycled between 1 V and 50 mV while XRD data was acquired. In this study 4 different electrodes containing 0, 20 %wt., 30 %wt. and 70 %wt. of Si in the active material of the electrode were cycled at C/5, C/2, 1C and 2C rates.Analysis of the XRD results showed that tracking of the evolution of graphite main reflections during electrochemical cycling while completely avoiding the copper signal has been achieved. The degree of graphite lithiation was tracked by following the distinct 002, 100 and 110 peaks of graphite where phase transitions to LiC12 and LiC6 can be identified. Consistent with the results of other studies, graphite has been found to be both lithiated and delithiated at lower potentials than silicon [ 3 ]. Increasing silicon content was found to decrease the degree of graphite lithiation as silicon will be preferentially lithiated. Increasing the current density was found to reduce the overall degree of lithiation of graphite as the specific capacity decreases and the material is not sufficiently lithiated to undergo the expected phase transitions. This study has therefore unraveled the effect of silicon content and current density on composite anode behavior which could allow for the design of better next-generation composite anodes. Tarascon, J.-M. & Armand, M. Issues and challenges facing rechargeable lithium batteries. Nature 414, 359–367 (2001). Ashuri, M., He, Q. & Shaw, L. L. Silicon as a potential anode material for Li-ion batteries: where size, geometry and structure matter. Nanoscale 8, 74–103 (2015). Moyassari, E. et al. The Role of Silicon in Silicon-Graphite Composite Electrodes Regarding Specific Capacity, Cycle Stability, and Expansion. J. Electrochem. Soc. 169, 010504 (2022). Drozhzhin, O. A. et al. An electrochemical cell with sapphire windows for operando synchrotron X-ray powder diffraction and spectroscopy studies of high-power and high-voltage electrodes for metal-ion batteries. J. Synchrotron Radiat. 25, 468–472 (2018). Figure 1

Structural and vibrational properties of cage-type Sc5Ru6Sn18 superconductor under pressure using synchrotron X-ray diffraction and Raman spectroscopy

We report detailed structural investigations of cage-type quasi-skutterudite compound Sc5Ru6Sn18 using synchrotron single-crystal and powder x-ray diffraction. Single-crystal x-ray diffraction studies at ambient temperature revealed that the Sc5Ru6Sn18 compound has a tetragonal symmetry in the I41/acd space group setting with a = 13.58Å and c = 27.14Å, similar to other R5Rh6Sn18 (R = Y, Sc, Lu) cage-type compounds. The electrical resistivity ρ(T) revealed the presence of a sharp superconducting (SC) transition at Tc = 4.07K. The ρ(T) of Sc5Ru6Sn18 above Tc shows a smooth decrease with decreasing temperature without any evident anomalies. Systematic temperature dependent synchrotron x-ray powder diffraction (XRPD) studies covering 400 to 110K shows that the Sc5Ru6Sn18 system remain in the tetragonal I41/acd structure in this temperature range without any anomalous behaviour in the unit-cell parameters. High-pressure (HP) synchrotron XRPD revealed a smooth reduction in the unit-cell parameters up to ~7GPa which can be well described by a third-order Birch-Murnaghan equation providing the bulk modulus of the system to be ~102.6GPa. This system is found to several Raman modes below 300cm-1. We could follow the pressure evolution of four Raman modes, all of which show a smooth hardening with pressure up to ~7GPa. Our results call for systematic HP studies of the SC properties of the title system.

High-pressure syntheses, crystal structures, and magnetic properties of novel quadruple perovskite oxides LaMn3Ru2Mn2O12 and LaMn3Ru2Fe2O12

Quadruple perovskite oxides LaMn3Ru2M2O12 (M = Mn, Fe) have been synthesized under high-pressure and high-temperature conditions of 8 GPa and 1373 K. Synchrotron X-ray powder diffraction study demonstrates that both oxides crystallized in AA'3B4O12-type cubic quadruple perovskite structures, where the Ru and M ions did not form the special ordering at B-site. X-ray absorption spectroscopy reveals that the valence states are represented as LaMn3+3Ru3+2M3+2O12 (M = Mn, Fe) in the ionic models, indicating that the isovalent states of Ru3+ and M3+ ions disturb the B-site ordering. Magnetization, heat capacity, and neutron diffraction data prove that short-range magnetic orderings are predominant for both compounds instead of long-range magnetic orderings. We conclude that the competition between ferromagnetic and antiferromagnetic superexchange interactions between Ru3+ and M3+ ions at B-site prevent the long-range magnetic ordering Mn3+ ions at A′-site, although the A'- and B-site magnetic sublattices are expected to be intrinsically independent in A′-Mn quadruple perovskite system. This finding represents that the atomic ordering of the B-site is essential for the precise design of magnetic structures for the LaMn3M2M′2O12 quadruple perovskite series.

Thermal stability of templated ZSM-5 zeolites: An in-situ synchrotron X-ray powder diffraction study

The topological symmetry of the as-synthesized ZSM-5 is orthorhombic Pnma, with 12 crystallographically independent tetrahedral sites in the unit cell. Highly crystallized ZSM-5 zeolite can be synthesized using organic species as structure directing agents (SDA), including tetra-n-propylammonium (TPA) and Na cations. This work investigates the thermal stability and high temperature structural evolution by in situ synchrotron (X-Ray) powder diffraction of TPA-ZSM-5 with different Si/Al ratios (15, 25, 50, and 100) and their structural modifications induced by template calcination. Rietveld refinements of the room temperature data revealed that in all samples tetrapropylammonium ions are located at the intersection of the sinusoidal and the straight channels. The refined TPA+ content increases with the increasing of the Si/Al ratio of the zeolite, reaching the theoretical value of 4 when the Si/Al ratio = 84, in very good agreement with both chemical and thermogravimetric analyses. The bond distances evidenced the lack of interactions between the TPA+ and the framework oxygen atoms. The high temperature refinements confirmed the high thermal stability of all four ZSM-5 samples, which remain crystalline until the end of the thermal treatment (800 °C). Burning of the template does not cause any relevant variations in the framework geometry and channel shape, confirming the high flexibility of the MFI framework.In addition, thermal analysis proved insights about the effect of aluminum content on the interaction between SDA and zeolite structure.

An Improved Model for Biogenic Ammonium Urate.

The pathological crystallization of ammonium urate inside the urinary tract is a well-documented medical condition; however, structural studies of the biogenic material have proven challenging owing to its propensity to precipitate as a powder and to exhibit diffraction patterns with widely varying intensities. Using block Rietveld refinement methods of powder diffraction data, here we identify ammonium urate hydrate (AUH) as a likely component in natural uroliths. AUH has a planar 2-D hydrogen-bonded organic framework of urate ions separated by ammonium ions with water molecules residing in bisecting channels. AUH is stable up to 150 °C for short time periods but begins to decompose with prolonged heating times and/or at higher temperatures. Changes in the solid-state structure and composition of synthetic material over a temperature range from 25 to 300 °C are elucidated through thermogravimetric and spectroscopic data, combustion analysis, and time-resolved synchrotron powder X-ray diffraction studies. We contend that biogenic ammonium urate is more accurately modeled as a mixture of AUH and anhydrous ammonium urate, in ratios that can vary depending on the growth environment. The similar but not identical diffraction patterns of these two forms likely account for much of the variability seen in natural ammonium urate samples.

Dehydration of Niclosamide Monohydrate Polymorphs: Different Mechanistic Pathways to the Same Product.

Many active pharmaceutical ingredients (APIs) can crystallize as hydrates or anhydrates, the relative stability of which depends on their internal structures as well as the external environment. Hydrates may dehydrate unexpectedly or intentionally, though the molecular-level mechanisms by which such transformations occur are difficult to predict a priori. Niclosamide is an anthelmintic drug on the World Health Organization's "List of Essential Medicines" that crystallizes in two monohydrate forms: HA and HB. Through complementary time-resolved synchrotron powder X-ray diffraction and thermogravimetric kinetic studies, we demonstrate that the two monohydrates dehydrate via distinctly different solid state pathways yet yield the same final anhydrate phase. Water loss from HA via diffusion yields an isomorphous desolvate intermediate which can rearrange to at least two different polymorphs, only one of which exhibits long-term stability. In contrast, dehydration of HB proceeds via a surface nucleation process where simultaneous water loss and product formation occur with no detectable crystalline intermediates. Comparative analysis of the two systems serves to highlight the complex relationship between lattice structure and solid state dehydration processes.

Noncryogenic Air Separation Using Aluminum Formate Al(HCOO)3 (ALF)

Separating oxygen from air to create oxygen-enriched gas streams is a process that is significant in both industrial and medical fields. However, the prominent technologies for creating oxygen-enriched gas streams are both energy and infrastructure intensive as they use cryogenic temperatures or materials that adsorb N2 from air. The latter method is less efficient than the methods that adsorb O2 directly. Herein, we show, via a combination of gas adsorption isotherms, gas breakthrough experiments, neutron and synchrotron X-ray powder diffraction, Raman spectroscopy, and computational studies, that the metal-organic framework, Al(HCOO)3 (ALF), which is easily prepared at low cost from commodity chemicals, exhibits substantial O2 adsorption and excellent time-dependent O2/N2 selectivity in a range of 50-125 near dry ice/solvent (≈190 K) temperatures. The effective O2 adsorption with ALF at ≈190 K and ≈0.21 bar (the partial pressure of O2 in air) is ≈1.7 mmol/g, and at ice/salt temperatures (≈250 K), it is ≈0.3 mmol/g. Though the kinetics for full adsorption of O2 near 190 K are slower than at temperatures nearer 250 K, the kinetics for initial O2 adsorption are fast, suggesting that O2 separation using ALF with rapid temperature swings at ambient pressures is a potentially viable choice for low-cost air separation applications. We also present synthetic strategies for improving the kinetics of this family of compounds, namely, via Al/Fe solid solutions. To the best of our knowledge, ALF has the highest O2/N2 sorption selectivity among MOF adsorbents without open metal sites as verified by co-adsorption experiments..

Nature of magnetic transitions and evidence for magnetoelastic coupling in the biskyrmion-host hexagonal compound MnNiGa

The hexagonal compound MnNiGa with Ni2In-type structure has emerged as an important biskyrmion-host system in which these textures are super-stable over a wide temperature range extending from 16 K to the Curie temperature TC ∼350 K under moderate fields. Both the intensity of the external magnetic field and the presence of magnetoelastic coupling are known to play key role in the stability of the skyrmionic textures. Here we present the results of the first comprehensive investigation of the order of the phase transitions and its field dependence along with magnetoelastic (i.e., spin-lattice) coupling using a combined magnetization and high-resolution synchrotron x-ray powder diffraction (SXRPD) study of MnNiGa. The temperature dependence of the magnetization M(T) exhibits a paramagnetic to collinear ferromagnetic (FM) transition at TC (∼347 ± 0.5 K) with thermal hysteresis and negative slope in the Arrott plots across the TC suggesting its first order character. The M(T) plot in the collinear FM phase exhibits an anomalously decreasing behaviour after reaching its peak value at 300 K followed by a step-like change below 210 K due to an additional spin reorientation transition (SRT) to a non-collinear FM phase with TSRT∼200 ± 1 K. The SRT also shows thermal hysteresis characteristic of a first order phase transition. Our field dependent studies reveal stabilization of the collinear FM phase to higher temperatures and destabilization of the SRT transition setting an upper limit on the magnetic field for the observation of biskyrmions in this system. The Rietveld analysis of the SXRPD data reveals anomalies in the unit cell parameters at TC and TSRT without any change in the crystal symmetry. The modelling of the temperature dependence of the unit cell volume in terms of the Debye-Grüneisen equation reveals significant deviation from phonon contributions and the presence of the quadratic spin-lattice coupling below the FM TC, in the precursor SRT regime as well as below TSRT. The present results on the magnetoelastic coupling in the hexagonal MnNiGa may provide the necessary insight towards understanding the extreme sensitivity of the magnetic skyrmionic textures to external stresses.

Beyond the ionic radii: A multifaceted approach to understand differences between the structures of LnNbO4 and LnTaO4 fergusonites

Synchrotron X-ray powder diffraction methods have been used to obtain accurate structures of the lanthanoid tantalates, LnTaO4, at room temperature. Three different structures are observed, depending on the size of the Ln cation: P21/c (Ln = La, Pr), I2/a (Ln = Nd-Ho), and P2/c (Ln = Tb-Lu). BVS analysis indicated that TaV is six-coordinate in these structures, with four short bonds and two longer bonds. Synchrotron X-ray powder diffraction methods were also used to observe the impact of Ta doping on the orthoniobates, Ln(Nb1-xTax)O4 (Ln = Pr, Nd, Sm, Gd, Tb, Dy, Ho, Yb, and Lu). Where both the niobate and tantalate oxide were isostructural (fergusonite structure, space group I2/a), complete solid solutions were prepared. In these solid solutions, the unit cell volume decreases as the Ta content increases. The subtle interaction evident between the LnO8 and BO6 sublattices in the fergusonite-type oxides was not observed in the related pyrochlore oxides. A combined synchrotron X-ray and neutron powder diffraction study of the series Ho(Nb1-xTax)O4 was used to determine accurate atomic positions of the anions, and hence, bond lengths. This revealed a change in the (Nb/Ta)-O bond lengths, reflective of the difference in the valence orbitals of Nb(4d) and Ta(5d). Examination of the partial density of states demonstrates differences in the electronics between Nb and Ta, leading to a difference in the bandgap. This study highlights the importance of the long B-O contacts in the fergusonite structures, and its potential impact on the I2/a to I41/a phase transition.

Robust evidence for the stabilization of the premartensite phase in Ni-Mn-In magnetic shape memory alloys by chemical pressure

The thermodynamic stability of the premartensite (PM) phase has been a topic of extensive investigation in shape memory alloys as it affects the main martensite phase transition and the related physical properties. In general, the PM phase is stable over a rather narrow temperature-composition range. We present here evidence for chemical pressure induced suppression of the main martensite transition and stabilization of the PM phase over a very wide temperature range from 300 K to around 5 K in a magnetic shape memory alloy (MSMA) Ni50Mn34In16 using magnetic susceptibility, synchrotron X-ray powder diffraction (SXRPD) studies and first-principles calculations. The ac-susceptibility studies show a highly skewed and smeared peak around 300 K without any further transition up to the lowest temperature of our measurement (5 K) for around 5% Al substitution. The temperature evolution of the SXRPD patterns confirms the appearance of the PM phase related satellite peaks at and below 300 K without any splitting of the main austenite (220) peak showing preserved cubic symmetry. This is in marked contrast to the temperature evolution of the SXRPD patterns of the martensite phase of the Al free as well as around 3% Al substituted compositions where the austenite (220) peak shows a clear splitting due to Bain distortion/symmetry breaking transition. Our theoretical calculations support the experimental findings and reveal that the substitution at the In site by a smaller size atom, like Al, can stabilize the PM phase with preserved cubic symmetry. Our results demonstrate that Al-substituted Ni-Mn-In MSMAs provide an ideal platform for investigating the physics of various phenomena related to the PM state.

In Situ X-ray Diffraction Investigation of the Crystallisation of Perfluorinated CeIV -Based Metal-Organic Frameworks with UiO-66 and MIL-140 Architectures*.

We report on the results of an in situ synchrotron powder X-ray diffraction study of the crystallisation in aqueous medium of two recently discovered perfluorinated CeIV -based metal-organic frameworks (MOFs), analogues of the already well investigated ZrIV -based UiO-66 and MIL-140A, namely, F4_UiO-66(Ce) and F4_MIL-140A(Ce). The two MOFs were originally obtained in pure form in similar conditions, using ammonium cerium nitrate and tetrafluoroterephthalic acid as reagents, and small variations of the reaction parameters were found to yield mixed phases. Here, we investigate the crystallisation of these compounds, varying parameters such as temperature, amount of the protonation modulator nitric acid and amount of the coordination modulator acetic acid. When only HNO3 is present in the reaction environment, only F4_MIL-140A(Ce) is obtained. Heating preferentially accelerates nucleation, which becomes rate determining below 57 °C. Upon addition of AcOH to the system, alongside HNO3 , mixed-phased products are obtained. F4_UiO-66(Ce) is always formed faster, and no interconversion between the two phases occurs. In the case of F4_UiO-66(Ce), crystal growth is always the rate-determining step. A higher amount of HNO3 favours the formation of F4_MIL-140A(Ce), whereas increasing the amount of AcOH favours the formation of F4_UiO-66(Ce). Based on the in situ results, a new optimised route to achieving a pure, high-quality F4_MIL-140A(Ce) phase in mild conditions (60 °C, 1 h) is also identified.

Thermal behavior of groundwater-saturated Korean buffer under the elevated temperature conditions: In-situ synchrotron X-ray powder diffraction study for the montmorillonite in Korean bentonite

In most countries, the thermal criteria for the engineered barrier system (EBS) is set to below 100 °C due to the possible illitization in the buffer, which will likely be detrimental to the performance and safety of the repository. On the other hand, if the thermal criteria for the EBS increases, the disposal density and the cost-effectiveness for the high-level radioactive wastes will dramatically increase. Thus, fundamentals on the thermal behavior of the buffer under the elevated temperatures is of crucial importance. Yet, the behaviors at the elevated temperatures of the bentonite under groundwater-saturated conditions have not been reported to-date. Here, we have developed an in-situ synchrotron-based method for the thermal behavior study of the buffer under the elevated temperatures (25–250 °C), investigated d-spacings of the montmorillonite in the Korean bentonite (i.e., Ca-type) at dry and KURT (KAERI Underground Research Tunnel) groundwater-saturated conditions (KJ-ii-dry and KJ-ii-wet), and compared the behaviors with that of MX-80 (i.e., Na-type, MX-80-wet). The hydration states analyzed show tri-, bi-, and mono-hydrated at 25, 120, and 250 °C, respectively for KJ-ii-wet, whereas tri-, mono-, and de-hydrated at 25, 150, and 250 °C, respectively for MX-80-wet. The Korean bentonite starts losing the interlayered water at lower temperatures; however, holds them better at higher temperatures as compared with MX-80.

Breakdown of the linear physical behavior in a solid solution of a halometallate molten salt, (dimim)[Fe(Cl1−xBrx)4] 0 ≤ x ≤ 1

Eighteen samples of the (dimim)[Fe(Cl1−xBrx)4] 0 ≤ x ≤ 1 solid solution were prepared in a one-pot synthesis. Single crystal and synchrotron X-ray powder diffraction studies show that all compounds are isomorphous with an orthorhombic structure (Ama2 space group) at room temperature. The crystal structure of these imidazolium molten salts can be described as layers of (dimim)+ cations (dimim = 1,3-dimethyl-imidazolium) extended in the bc-plane with an antiparallel stacking along the a-axis forming a herring-bond motive. The (FeX4)− (X = Cl and Br) anions form layers extended on the bc-plane that are intercalated between the organic layers and inverted with respect to the adjacent layer along the a direction. The evolution of the cell volume at this temperature follows the Vegard's law in the whole range of substitution with ∆V ≈ 115 Å3 between non-substituted phases, showing a non-linear axial expansion in the b and c directions. In addition, the melting point of the solid solution does not follow the expected linear physical behavior. Finally, the magnetic study indicates the existence of overall antiferromagnetic interactions as predominant, which are stronger with the increase in the (FeBr4)− ion substitution. However, it was found that the 3D magnetic ordering of the non-substituted phases vanishes or it is below the minimum temperature reachable by the magnetometer devices (1.8 K) for the 25–50% bromide substitutions. This is connected with the appearance of different crystal phases as function of bromide composition at low temperature.

High pressure behaviour of tobermorite supergroup minerals: An in situ synchrotron X-ray powder diffraction study

The high-pressure behaviour of two natural samples of kenotobermorite [Ca4Si6O15(OH)2·5H2O] and clinotobermorite [Ca5Si6O17·5H2O] has been studied by in situ synchrotron X-ray powder diffraction. The samples were compressed in silicone oil using a diamond anvil cell. The calculated bulk moduli are as following: kenotobermorite K0 = 83.2 ± 0.4 GPa and clinotobermorite K0 = 93.5 ± 0.8 GPa. The presence of “zeolitic” Ca in clinotobermorite induces a lower compressibility in this sample. The comparison of the current results with previous studies evidenced that experimentally determined bulk moduli are generally higher than those obtained by theoretical calculations and the differences are related to the configuration of the silicate chains as well as to the content of “zeolitic” cations and H2O molecules.

Comparative Compressibility of Smectite Group under Anhydrous and Hydrous Environments.

High-pressure synchrotron X-ray powder diffraction studies of smectite group minerals (beidellite, montmorillonite, and nontronite) reveal comparative volumetric changes in the presence of different fluids, as pressure transmitting media (PTM) of silicone oil and distilled water for anhydrous and hydrous environments at room temperature. Using silicone oil PTM, all minerals show gradual contraction of unit-cell volumes and atomistic interplane distances. They, however, show abrupt collapse near 1.0 GPa under distilled water conditions due to hydrostatic to quasi-hydrostatic environmental changes of water PTM around samples concomitant with the transition from liquid to ICE-VI and ICE-VII. The degrees of volume contractions of beidellite, montmorillonite, and nontronite up to ca. 3 GPa are ca. 6.6%, 8.9%, and 7.5% with bulk moduli of ca. 38(1) GPa, 31(2) GPa, and 26(1) GPa under silicone oil pressure, whereas 13(1) GPa, 13(2) GPa, and 17(2) GPa, and 17(1) GPa, 20(1) GPa, and 21(1) GPa under hydrostatic and quasi-hydrostatic environments before and after 1.50 GPa, respectively.

Structural Characterization and Comparison of Monovalent Cation-Exchanged Zeolite-W.

We report comparative structural changes of potassium-contained zeolite-W (K-MER, structural analogue of natural zeolite merlinoite) and monovalent extra-framework cation (EFC)-exchanged M-MERs (M = Li+, Na+, Ag+, and Rb+). High-resolution synchrotron X-ray powder diffraction study precisely determines that crystal symmetry of MERs is tetragonal (I4/mmm). Rietveld refinement results reveal that frameworks of all MERs are geometrically composed of disordered Al/Si tetrahedra, bridged by linkage oxygen atoms. We observe a structural relationship between a group of Li-, Na-, and Ag-MER and the group of K- and Rb-MER by EFC radius and position of M(1) site inside double 8-membered ring unit (d8r). In the former group, a-axes decrease reciprocally, c-axes gradually extend by EFC size, and M(1) cations are located at the middle of the d8r. In the latter group, a- and c-axes lengths become longer and shorter, respectively, than axes of the former group, and these axial changes come from middle-to-edge migration of M(1) cations inside the d8r channel. Unit cell volumes of the Na-, Ag-, and K-MER are ca. 2005 Å3, and the volume expansion in the MER series is limited by EFC size, the number of water molecules, and the distribution of extra-framework species inside the MER channel. EFC sites of M(1) and M(2) show disordered and ordered distribution in the former group, and all EFC sites change to disordered distribution after migration of the M(1) site in the latter group. The amount of water molecules and porosities are inversely proportional to EFC size due to the limitation of volume expansion of MERs. The channel opening area of a pau composite building unit and the amount of water molecules are universally related as a function of cation size because water molecules are mainly distributed inside a pau channel.

Ru doping effect on the structural, electronic, transport, optical and dye degradation properties of layered Li2MnO3

Ru doped Li2MnO3 compositions show the presence of redox couples Mn+3–Mn+4 and Ru+4–Ru+5. Due to the presence of these redox couples in Li2Mn1−xRuxO3 (x = 0.05, 0.1), Ru doped compositions show (i) change in structure (ii) large decrease in impedance(~ 107 to ~ 105 Ohm) (iii) degrade methyl orange and methylene blue solution (pH-6) in quick time in presence of tungsten (W) bulb and sun light. Synchrotron X-ray powder diffraction studies show the change in lattice parameters with Ru doping at Mn site in Li2Mn1−xRuxO3 (x = 0.05, 0.1). Raman and Infrared spectroscopic studies show the shift in Mn–O stretching mode of Li2MnO3 towards lower wave number with Ru doping. Soft X-ray absorption spectroscopic studies show the presence of mixed valences of Mn+3, Mn+4, Ru+4 and Ru+5 in Li2Mn1−xRuxO3 (x = 0.05, 0.1) using L2,3 and M4 edge. UV–Vis diffuse reflectance spectroscopic studies show the optical band gap in visible light range in Ru doped Li2Mn1−xRuxO3 (x = 0.05, 0.1) compositions. The presence of 5 mg of Li2Mn0.9Ru0.1O3 degrades 5 ml of methyl orange solution (10 mg/L) of pH 6 in 5 min and methylene blue solution (10 mg/L) of pH 6 in 3 min of exposure in W bulb light.

In Situ Synchrotron XRD and sXAS Studies on Li-S Batteries with Ionic-Liquid and Organic Electrolytes

Lithium-sulfur (Li-S) batteries are a promising technology capable of reaching high energy density of 500–700 Wh kg−1, however the practically achievable performance is still lower than this value. This hindrance can be attributed to a lack of understanding of the fundamental electrochemical processes during Li-S battery cycling, in particular the so-called redox shuttle effect which is due to the relatively high solubility of polysulfide intermediates in the electrolyte. Herein, the effects of LiNO3 as an additive as well as C4mpyr-based ionic liquids (ILs) in electrolyte formulations for Li-S cells are analysed using in situ X-ray powder diffraction (XRD) and ex situ soft X-ray absorption spectroscopy (sXAS) techniques. Whilst LiNO3 is known for its protective properties on the lithium anode in Li-S cells, our studies have provided further evidence for suppression of Li2S deposition when using LiNO3 as an additive, as well as affecting the solid electrolyte interphase (SEI) layer at a molecular level. Moreover, the detected sulfur species on the surface of the anode and cathode, after a few cycles are compared for IL and organic-based electrolytes.

Solid solution formation in the metatorbernite-metazeunerite system (Cu(UO2)2(PO4)2- x(AsO4) x. nH2O) and their stability under conditions of variable temperature.

Mineral phases which can be thought of as members of a metatorbernite-metazeunerite solid solution (Cu(UO2)2(PO4)2- x(AsO4) x.8H2O have been identified in radioactive samples from spoil heaps at the uranium mine site in South Terras, Cornwall (grid reference SW935523). A complete solid solution (0 < x < 2) was synthesized by precipitation from solution using uranium (VI) nitrate and copper (II) chloride and phosphoric acid/arsenic acid in the appropriate molar proportions. Refined unit cell parameters determined by Pawley fitting of powder X-ray diffraction data showed a linear variation in the a unit cell parameter according to Vegard's Law, allowing the composition of the natural mineral phases found at South Terras to be determined from measurement of their unit cell parameters. High-resolution variable-temperature synchrotron powder X-ray diffraction studies were carried out at the Diamond Light Source on three members of this solid solution ( x = 0, 1, 2) and showed different structural behaviour as a function of composition and temperature. Metatorbenite ( x = 0) retains its tetragonal symmetry at low temperatures and dehydrates to an amorphous phase at 473 K, whereas metazeunrite ( x = 2) transforms to an orthorhombic phase at low temperatures, regains its tetragonal symmetry on heating to 323 K and undergoes a further transition to an, as yet, unidentified phase at 473 K. This article is part of the theme issue 'Fifty years of synchrotron science: achievements and opportunities'.