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The effect of MgO on the stability, concentrations and formation mechanisms of silico-ferrite of calcium and aluminum (SFCA and SFCA-I) iron ore sinter bonding phases during heating in synthetic mixtures was investigated using in situ x-ray diffraction. The novelty of this study is in the intricate detail in which the formation mechanisms of the SFCA-I and SFCA phases are characterized, and the observation of the effects of MgO addition on intermediate phases. For example, the significant mechanistic effect of increasing MgO content is the lack of additional SFCA formed after SFCA-I decomposition, with additional magnesioferrite spinel being formed instead. In MgO-free mixtures, the decomposition of SFCA-I typically results in a significant increase in SFCA concentration. Through the results of phase equilibria experiments, this study also provides evidence that the SFCA-I structure accommodates more Mg2+ than the SFCA structure, which is consistent with evidence that the SFCA-I structure contains a higher amount of Fe2+ than SFCA.

Sodium-ion batteries (NIBs) are an emerging alternative to lithium-ion batteries because of abundant sodium re-sources and the potentially lower cost. Here we report the Na0.7MnO2 solid-state synthesized at 1000 oC which shows two distinct phases, one adopts hexagonal P2-type P63/mmc and the other adopts orthorhombic Pbma space group symmetry. The phase ratio of the P2 to orthorhombic phase is 55.0(5):45.0(4). A single phase P2 structure is found to form at 1000 oC after modification with alkali metals Rb and Cs while the K-modified produces an additional minor impurity. Modification is the addition of the alkali elements during synthesis which do not appear to dope into the crystal structure. As a cathode for NIBs, parent Na0.7MnO2 shows a second charge/discharge capacity of 143/134 mAh g-1, K-modified Na0.7MnO2 184/178 mAh g-1, Rb-modified Na0.9MnO2 159/150 mAh g-1 and Cs-modified Na0.7MnO2 171/163 mAh g-1 between 1.5-4.2 V at a current density of 15 mA g-1. The parent Na0.7MnO2 is compared with alkali metal (K, Rb and Cs) modified NaxMnO2 in terms of surface morphology using scanning transmission electron micros-copy coupled with energy-dispersive X-ray spectroscopy (STEM-EDS), scanning electron microscopy (SEM), 23Na sol-id-state nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), electrochemical performance and structural electrochemical evolution using in situ/operando synchrotron X-ray diffraction (SXRD).

The double perovskite Ba2CoOsO6, synthesized using solid-state methods at ambient pressure, is shown as a rare example of an oxide adopting the 6L-trigonal (S.G.: P3m1) perovskite structure. The s...

CO2 hydrogenation is one route for partial CO2 abatement while producing valuable chemical products. Cu/CeO2 catalysts have attracted great interest as materials that facilitate the efficient hydrogenation of CO2 into methanol and CO. This paper investigates the effect of preparation methods on the structure, function and activity of Cu/CeO2 catalysts. The catalysts have been prepared by deposition–precipitation (DP) and the co-precipitation (CP) methods. The activity tests for the catalysts were conducted in a high-pressure packed bed reactor in the temperature range of 200–300 °C at 50 bar pressure. The DP catalyst showed higher methanol productivity and lower methanol selectivity compared its CP counterpart. The reasons for the higher performance of the DP catalyst and other structural and functional differences have been investigated through in-depth characterization using synchrotron radiated in-situ powder diffraction, DRIFTS, XPS, HR-TEM, TPR and N2O decomposition used to determine copper surface area. The higher methanol productivity in the DP catalyst was attributed to the higher Cu surface area and dispersion. Additionally, the in-situ synchrotron-based powder diffraction measurements provide fundamental insights on the interesting differences in the CeO2 structure i.e. the lattice parameter and the lattice microstrain during the reduction step that could be attributed to the size difference in the CeO2 support nanoparticles.

The structure and thermal expansion of the astronomical molecule propionitrile have been determined from 100 to 150 K using synchrotron powder X-ray diffraction. This temperature range correlates with the conditions of Titan's lower stratosphere, and near surface, where propionitrile is thought to accumulate and condense into pure and mixed-nitrile phases. Propionitrile was determined to crystallize in space group, Pnma (No. 62), with unit cell a = 7.56183 (16) Å, b = 6.59134 (14) Å, c = 7.23629 (14), volume = 360.675 (13) Å3 at 100 K. The thermal expansion was found to be highly anisotropic with an eightfold increase in expansion between the c and b axes. These data will prove crucial in the computational modelling of propionitrile–ice systems in outer Solar System environments, allowing us to simulate and assign vibrational peaks in the infrared spectra for future use in planetary astronomy.

Synchrotron X-ray powder diffraction methods have been used to obtain accurate structures of the lanthanoid orthoniobates, LnNbO4 at room temperature. The observed decrease in the unit cell volume in going from Ln = La to Lu correlates with a decrease in the volume of the LnO8 polyhedra due to the changing size of the Ln3+ cation. In all cases the Nb is in a highly distorted six-coordinate geometry with two long, ~2.5 A, and four short ~1.9 A Nb–O distances. The importance of the long Nb–O bonds is evident from Bond Valence Sum Calculations. Variable temperature structural studies of three examples, Ln = La, Sm and Gd, showed each transformed to a high temperature tetragonal scheelite type structure in space group I41/a. In the high temperature structure the Nb are tetrahedrally coordinated and it appears that monoclinic – tetragonal transition is best described as a reconstructive transition in which the long Nb–O(1) bond is broken upon heating.

This paper reports the critical role of microstructural length scale in dealloying for the fabrication of bimodal or monolithic functional nanoporous metal structures and the underlying mechanisms and kinetics. Two dual-phased (Al2Cu AlCu) precursor alloys Al65Cu35 and Al55Cu45 (at.%) were selected to demonstrate the concept. Microstructural observations revealed that the two constituent phases Al2Cu and AlCu in each alloy can undergo either sequential dealloying, which leads to bimodal nanoporous Cu, or simultaneous dealloying, which results in monolithic nanoporous Cu. In-situ and ex-situ synchrotron X-ray diffraction (XRD), focused ion beam scanning electron microscopy (FIB-SEM), and potentiodynamic polarization scans were used to identify the detailed phase evolution processes and kinetics. It is concluded that microstructural length scale plays a decisive role in regulating the dealloying pathways. Sequential dealloying of Al2Cu and AlCu occurs when both phases are micrometer-scaled, while simultaneous dealloying takes over when both phases are nanoscaled. The nanosize effect of Al2Cu and AlCu can override their intrinsic difference in electrochemical potential at the micro- or macro-scale, and the advantage of tetragonal Al2Cu over monoclinic AlCu in crystallographic transition to face-centered-cubic (FCC) Cu by dealloying. The high-resolution in-situ synchrotron XRD data revealed a two-stage kinetic process for dealloying of Al2Cu to Cu. The Avrami-Erofe′ev kinetic model provides an excellent description of each stage. The underlying rationales and implications are discussed.

In this study, we have examined ceramic matrix composites with silicon carbide fibers in a melt-infiltrated silicon carbide matrix (SiC/SiC). We subjected samples to tensile loads while collecting micro X-ray computed tomography images. The results showed the expected crack slowing mechanisms and lower resistance to crack propagation where the fibers ran parallel and perpendicular to the applied load respectively. Cracking was shown to initiate not only from the surface but also from silicon inclusions. Post heat-treated samples showed longer fiber pull-out than the pristine samples, which was incompatible with previously proposed mechanisms. Evidence for oxidation was identified and new mechanisms based on oxidation or an oxidation assisted boron nitride phase transformation was therefore proposed to explain the long pull-out. The role of oxidation emphasizes the necessity of applying oxidation resistant coatings on SiC/SiC.

The orthorhombic mineral moolooite, CuC2O4. nH2O, described by Clarke and Williams (1986) using Debye-Scherrer photographic data, has a fully-disordered stacking fault (FDSF) structure. Related monoclinic models have been reported for various synthesised samples based on Schmittler (1968). In the present study, synchrotron radiation diffraction data for moolooite and synthesised specimens have been examined with particular reference to crystallographic disorder. The moolooite data correspond to space group Pnnm, with a = 5.3064(2), b = 5.6804(2), c = 2.5630(1) Å; Vc = 77.26(1) Å3; and Z = 1; and the FDSF structure along the b-direction has been confirmed. The synthetic specimen data from the study indicate partial ordering, with space group P21/n; and the cell parameters for one specimen being a = 5.957(7), b = 5.611(5), c = 5.133(7) Å; β = 115.16(2)°; Vc = 155.27 Å3 and Z = 2. The level of zeolitic water in the materials has been considered using the approach of Schmittler based on thermogravimetry and pycnometry. The new data for natural topotype material correspond to CuC2O4.1.0H2O. It is postulated that the level of water for natural and synthetic specimens may be attributed to the conditions under which the material forms.

Sodium-ion batteries (NIBs) are an emerging alternative to lithium-ion batteries because of the abundance of sodium resources and their potentially lower cost. Here we report the Na

The double perovskite Ba

Domain-wall dynamics under strong, super-coercive electric fields in polycrystalline bismuth ferrite (BiFeO3) are not well established due to the experimental difficulties in processing high phase purity perovskite with low electrical conductivity. Overcoming these difficulties, here we present x-ray diffraction measurements carried out in situ during electrical poling with a trapezoidal electric-field to investigate the domain wall dynamics and lattice strain in this material. It is observed that during field ramping, microscopic strains, i.e., non-180° domain texture and lattice strain, increase simultaneously. During DC field dwell, however, a lattice strain decrease occurs over time, accompanied by an increase in the non-180° domain texture. This inverse time-dependent trend of microscopic strain mechanisms is speculated to be due to mobile charged defects residing in domain wall regions. The configuration of these charged point defects may also play a role in the observed post-poling relaxations of non-180° domain texture and macroscopic piezoelectric coefficients on removal of the field. Since conducting domain walls have been recently identified in a number of ferroelectrics, these results should significantly impact the understanding of strain mechanisms not only in BiFeO3 but on a broader range of ferroelectric materials. Locked until 23.3.2021 due to copyright restrictions. Published by AIP Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in JOURNAL and may be found at https://doi.org/10.1063/5.0002235

To promote accurate lattice-strain measurement and twinning observation during in situ deformation of age-hardenable lightweight magnesium alloys, a high-resolution X-ray diffraction technique was applied using medium-energy synchrotron X-rays (≤21 keV) coupled with a fast Mythen strip detector. This technique allows data collection in transmission geometry, with sufficient grain-sampling statistics achieved by rocking the samples during each measurement under step-wise uniaxial tensile/compressive loads. The capabilities of the method are demonstrated on a model age-hardenable Mg–Sn-based alloy in compression. The measurements confirm that this technique offers high angular resolution and a wide angular range, minimizing the problem of peak overlap, which is advantageous for accurate lattice-strain determination of both the α-Mg matrix and strengthening precipitate phases. The absolute strain resolution is approximately ±2 × 10−4. Lattice-strain partitioning and anisotropy in the α-Mg phase reveal the occurrence of microplasticity due to the activation of basal dislocation slip in Mg alloys and provide experimental information for characterizing the plastic anisotropy of the materials. The initiation and growth of {10 {\overline 1} 2} tension twins are identified and quantified from the changes in the integrated intensities of 10 {\overline 1} 0/0002 reflections as a function of stress. The critical resolved shear stresses (CRSSs) for the activations of basal slip and tension twin modes in both non-aged and aged materials were estimated. The results reveal that, after the ageing treatment, the CRSS value for basal slip increases from 18 to 33 MPa, an increase of ∼83%, and that for tension twinning increases from 32 to 52 MPa, an increase of ∼63%. The methodology also enables further microstructural data to be probed in situ. This includes the apparent area-weighted twin size and dislocation density during twin onset, and the precipitate volume fraction.

In situ synchrotron powder X-ray diffraction measurements have demonstrated that SrUO4 undergoes a reversible phase transformation under reducing conditions at high temperatures, associated with the ordering of oxygen defects resulting in a lowering of crystallographic symmetry. When substoichiometric rhombohedral α-SrUO4–x, in space group R3m with disordered in-plane oxygen defects, is heated above 200 °C in a hydrogen atmosphere it undergoes a first order phase transformation to a (disordered) triclinic polymorph, δ-SrUO4–x, in space group P1. Continued heating to above 450 °C results in the appearance of superlattice reflections, due to oxygen-vacancy ordering forming an ordered structure δ-SrUO4–x. Cooling δ-SrUO4–x toward room temperature results in the reformation of the rhombohedral phase α-SrUO4–x with disordered defects, confirming the reversibility of the transformation. This suggests that the transformation, resulting from oxygen vacancy ordering, is not a consequence of sample reduction or d...

The hydrogenation properties of Laves phases LnMg2 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Ho, Er, Tm, Yb) were investigated by thermal analysis, X-ray, synchrotron, and neutron powder diffraction. At 14.0 MPa hydrogen gas pressure and 393 K, PrMg2 and NdMg2 take up hydrogen and form the colorless, ternary hydrides PrMg2H7 (P41212, a = 632.386(6) pm, c = 945.722(11) pm) and NdMg2H7 (P41212, a = 630.354(9) pm, c = 943.018(16) pm). The crystal structures were refined by the Rietveld method from neutron powder diffraction data on the deuterides (PrMg2D7, P41212, a = 630.56(2) pm, c = 943.27(3) pm; NdMg2D7, P41212, a = 628.15(2) pm, c = 940.32(3) pm) and shown to be isotypic to LaMg2D7. The LaMg2D7 type of hydrides decompose at 695 K (La), 684 K (Ce), 684 K (Pr), 672 K (Nd), and 639 K (Sm) to lanthanide hydrides and magnesium. The Laves phase EuMg2 forms a hydride EuMg2Hx of black color. Its crystal structure (P212121, a = 664.887(4) pm, b = 1136.993(7) pm, c = 1069.887(7) pm) is closely related to the hexagona...

Graphite has been widely used as a negative electrode material in lithium-ion batteries, and recently it has attracted attention for its use in potassium-ion batteries. In this study, the firstin situX-ray diffraction characterisation of a K/graphite electrochemical cell is performed. Various graphite intercalation compounds are found, including the stage three KC36and stage one KC8compounds,along with the disappearance of the graphite during the potassiation process. These results show new insights on the non-equilibrium states of potassium-ion intercalation into graphite in K/graphite electrochemical cells.

The electrochemical behaviour of a number of Pb-based anode alloys, under simulated electrowinning conditions, in a 1.6 M H2SO4 electrolyte at 45 °C was studied. Namely, the evolution of PbO2 and PbSO4 surface layers was investigated by quantitative in situ synchrotron X-ray diffraction (S-XRD) and subsequent Rietveld-based quantitative phase analysis (QPA). In the context of seeking new anode alloys, this research shows that the industry standard Pb-0.08Ca-1.52Sn (wt%) anode, when exposed to a galvanostatic current and intermittent power interruptions, exhibited poor electrochemical performance relative to select custom Pb-based binary alloys; Pb–0.73Mg, Pb–5.05Ag, Pb–0.07Rh, and Pb–1.4Zn (wt%). The in situ S-XRD measurements and subsequent QPA indicated that this was linked to a lower proportion of β-PbO2, relative to PbSO4, on the Pb-0.08Ca-1.52Sn alloy at all stages of the electrochemical cycling. The best performing alloy, in terms of minimisation of overpotential during normal electrowinning operation and minimising the deleterious effects of repeated power interruptions – both of which are significant factors in energy consumption – was determined to be Pb–0.07Rh.

The structure of TcO2 between 25 and 1000 °C has been determined in-situ using powder diffraction methods and is found to remain monoclinic in space group P21/c. The thermal expansion in TcO2 is highly anisotropic with negative thermal ex-pansion of the b-axis observed above 700 °C. This is the result of an anomalous expansion along the a-axis that is a consequence of weakening of the Tc-Tc bonds. Australian Synchrotron Australian Research Council

Linking the accumulation of microstructural damage prior to crack initiation to the lifing of aero-engines components would help to better predict the time that a component spends in this crack initiation stage. We present the results and analysis of in-situ high-resolution X-ray diffraction (XRD) experiments of a Ti-6Al-4V specimen that experienced tensile loading using medium energy synchrotron X-rays (≤ 21 keV) carried out at the Australian Synchrotron. The XRD analysis characterised XRD line-broadening due to the build-up of dislocations and the formation of crystallites in α- and β-Ti-6Al-4V specimens. Using Bayesian XRD analysis methods, the density, spatial arrangement of dislocations, and crystallite size information for α- and β-phases of the Ti-6Al-4V was extracted from the XRD line-profiles, as a function of applied load. The XRD analysis was then compared and validated with transmission electron microscopy (TEM) analysis of the specimen before and after the loading. Comparison of the TEM and XRD analysis reveals broad agreement in terms of the microstructural damage of Ti-6Al-4V specimens.

The impact of aging on cyclic loading-unloading responses of extruded Mg-Zn alloys was investigated in compression. In-situ Synchrotron transmission X-ray diffraction and electron backscatter diffraction post-mortem analysis were performed. To aid interpretation additional tests were performed on tensile samples and on samples with lower levels of Zn. The effect of aging is seen to be complex. During initial loading, aging clearly promotes twinning over slip. However, twins in the aged sample are thinner than those in the non-aged material. Upon unloading, additional ‘forward’ twinning occurs in the aged samples and this then is followed by de-twinning. Non-aged samples display de-twinning but no additional forward twinning. With subsequent re-loading, non-aged samples display a re-loading yield effect while the aged samples do not. Aging also leads to a noticeable ratchetting strain. It is proposed that understanding these disparate phenomena requires consideration of the dislocation activity that relaxes the stresses within the highly stressed zones that surround twins and precipitates. Precipitation retards the relaxation of slip events occurring in the highly stressed zone at the twin periphery. At the same time, slip activity in the stressed regions surrounding non-deforming particles is proposed to lead to a creep-type phenomenon that redistributes load and creates the ratchetting effect seen during cyclic loading of aged samples. To model the cyclic response of aged magnesium alloys will require consideration of these complex relaxation effects.

The effect of basal plate precipitates on the hardening of basal slip and {101¯2} twinning modes was investigated for a non-aged and aged AZ91 alloy in the twin dominated strain paths. Exploiting in-situ synchrotron and laboratory based X-ray diffraction methodologies, we quantified the critical resolved shear stress (CRSS) for basal slip and twinning modes. The twin volume fraction changes were quantified from the intensity changes with applied load. We observed that the twin volume fraction changes with plastic strain is sensitive to the initial texture, while the relative hardening of different deformation modes are considered as a secondary effect. We also found that the twin interior stresses were significantly smaller and consistent with the high twin back stresses in the presence of precipitates. We propose, based on a simple analytical equation, that the leading edge of the propagating twin have a Burgers vector equivalent to 100 twinning dislocations and when the propagating twin is blocked by a precipitate, relatively high resolved stress is required for bowing the twin dislocation and hence the propagation of the twin occurs by the dissociation of the leading edge of the twinning dislocation.

Glassy metals exhibit a range of interesting properties including high strength and corrosion resistance, but often have poor toughness and tensile ductility in the fully amorphous state. It has been shown that combinations of desirable properties can be achieved by the partial crystallisation of glass-forming alloys, either during controlled solidification or by annealing a fully amorphous glass. The aim of this investigation is to understand the competition in phase formation during the crystallisation of metallic glasses in the Al-Ni-Y system. High-resolution, in situ synchrotron powder diffraction has been used to quantitatively follow the evolution of phases in 5 different alloys between Al87Ni9Y4 and Al75Ni15Y10, as they were continuously heated to melting and subsequently cooled back to ambient temperature. Upon heating, the first crystallisation product was found to vary from FCC Al to the intermetallic Al9Ni2 phase with increasing Ni concentration. In addition, the crystallisation sequence also changed from a two-stage to a three-stage process. High number densities of crystallites (∼1023 m−3) were observed initially for both FCC Al and Al9Ni2. Upon cooling, the partially disordered Al9Ni3Y phase was found to form preferentially over the intermetallic phases observed during heating. The difference in competition in phase formation during heating and cooling are discussed in terms of nucleation barriers calculated using a recent thermodynamic assessment of the Al-Ni-Y system. The role of compositional heterogeneities in the as-quenched glasses and long-range diffusion on the nucleation process is discussed.

The development of new insertion electrodes requires an in-depth understanding of the structure–function relationships in order to rationally develop better electrodes. Sodium layered oxides such as P2 Na2/3Fe1/2Mn1/2O2 and Na2/3Fe2/3Mn1/3O2 are particularly interesting due to their performance, price, and low toxicity. Using in situ synchrotron X-ray diffraction during electrochemical cycling of P2 Na2/3Fe0.4Mn0.6O2, changes in the phase composition, lattice parameters, and critically sodium content within the crystal structure are determined. Approaching the charged state, there is an increase in the interlayer distance, brought about via a subtle two-phase region that maintains the structure type as P2. Interestingly, this appears to stabilize the P2 structure in the charged state and inhibits the formation of the highly disordered and typically unfavorable “Z” or OP4 phases up to 4.2 V at 20 mA/g. At the discharged state, at least three phases are present, including P′2 and two subtly different P2 pha...

In situ neutron and synchrotron X-ray diffraction studies demonstrate that SrUO4 acts as an oxygen transfer agent, forming oxygen vacancies under both oxidizing and reducing conditions. Two polymorphs of SrUO4 are stable at room temperature, and the transformation between these is observed to be associated with thermally regulated diffusion of oxygen ions, with partial reduction of the U(6+) playing a role in both the formation of oxygen deficient α-SrUO4-δ and its subsequent transformation to stoichiometric β-SrUO4. This is supported by ab initio calculations using density functional theory calculations. The oxygen vacancies play a critical role in the first order transition that SrUO4 undergoes near 830 °C. The changes in the oxidation states and U geometry associated with the structural phase transition have been characterized using X-ray absorption spectroscopy, synchrotron X-ray diffraction, and neutron diffraction.

The structures of some AUO4 (A=Ca, Sr, or Ba) oxides have been determined using a combination of neutron and synchrotron X-ray diffraction, supported by X-ray absorption spectroscopic measurements at the U L3-edge. The smaller Ca cation favours a rhombohedral AUO4 structure with 8-coordinate UO8 moieties whilst an orthorhombic structure based on UO6 groups is found for BaUO4. Both the rhombohedral and orthorhombic structures can be stabilised for SrUO4. The structural studies suggest that the bonding requirements of the A site cation play a significant role in determining which structure is favoured. In the rhombohedral structure, Bond Valence Sums demonstrate the A site is invariably overbonded, which, in the case of rhombohedral α-SrUO4, is compensated for by the formation of vacancies in the oxygen sub-lattice. The uranium cation, with its flexible oxidation state, is able to accommodate this by inducing vacancies along its equatorial coordination site as demonstrated by neutron powder diffraction.

The importance of sample history on the Pbnm-Cmcm phase coexistence in NaTaO 3 has been investigated using high resolution neutron and synchrotron X-ray diffraction methods. These results reveal that the phase coexistence, associated with the first order Pbnm-Cmcm phase transition, is not significantly affected by the annealing conditions used to prepare the sample. Rather it is found that compositional inhomogeneities or defects play a significant role in stabilising the high temperature Cmcm phase at room temperature.

This contribution investigates the phase composition of CrN and CrAlN coatings by in-situ high temperature synchrotron radiation (SR-XRD), with the coatings deposited on steel substrate by closed field unbalance magnetron sputtering. Rietveld refinement on the SR-XRD spectra indicated CrN as the major phase, over the temperature range of 25 °C – 700 °C, for both coatings. At the high temperature of 700 °C, a Cr2N phase was observed in the CrN coating while the CrAlN coating also had a Cr phase. Williamson–Hall plots, from the refined data, afforded estimating variations of the strain and crystallite size of the major phase, up to 700 °C. The crystallite size (10 nm) for the CrAlN coating, at 25 °C, agrees very well with previous GI-XRD and TEM results obtained at room temperature Li et al. (2012).

Positive electrodes still limit the maximum attainable energy density of Na-ion batteries. Increasing the amount of electrochemically active transition metal is one way of improving energy density. However, this is complicated by the balance between initial capacity and structural stability/capacity retention. Here, the Mn-rich P2– Na2/3Mn0.9Fe0.05Ti0.05O2 is synthesised via the solid-state method and its structural evolution during operation, between 1.9 and 4.2 V, investigated. Through operando X-ray powder diffraction data, no evidence is found for the formation of Z, OP4 or O2 phases and the material primarily displays regions of two-phase coexistence. P2– Na2/3Mn0.9Fe0.05Ti0.05O2 delivers a second charge/discharge capacity of 152/164 mAh.g−1 at C/10, within the voltage range 4.0–2.0 V and retains 75% of the dis-charge capacity at the 50th cycle. A detailed comparison, in terms of both the electrochemical performance and structural evolution, to related Mn-rich phases is provided. The results further demonstrate that structural stability and battery performance can be improved through subtle co-substitutions.

In situ synchrotron powder X-ray diffraction measurements have demonstrated that SrUO

The crystal structures of the series of ordered double perovskites Ba(2-x)Sr(x)YIrO6 (0 ≤ x ≤ 2) were refined using a combination of high-resolution synchrotron X-ray and high-intensity neutron diffraction data. The materials displayed a sequence of structures Fm3m(a(0)a(0)a(0)) (x = 0.6)--> I4/m(a(0)a(0)c(-)) (x = 1.0)--> I2/m(a(-)a(-)c(0)) (x = 1.4)--> P2(1)/n(a(-)a(-)c(+)) associated with increased tilting of the corner-sharing octahedra induced by increasing amount of the smaller Sr cation present. A similar sequence of transitions was induced by heating selected samples. Magnetic susceptibility measurements between 2 and 300 K showed no evidence for long-range magnetic ordering, an observation that was supported by neutron diffraction measurements, and rather strong spin-orbit coupling results in a Jeff = 0 ground state.

We use in situ high-temperature X-ray diffraction (HT-XRD), ex-situ XRD and synchrotron X-ray absorption near edge structure spectroscopy (XANES) to derive fundamental insights into mechanisms of chromium oxidation during combustion of solid fuels. To mimic the real combustion environment, mixtures of pure eskolaite (Cr(3+)2O3), lime (CaO) and/or kaolinite [Al2Si2O5(OH)4] have been annealed at 600-1200 °C in air versus 1% O2 diluted by N2. Our results confirm for the first time that (1) the optimum temperature for Cr(6+) formation is 800 °C for the coexistence of lime and eskolaite; (2) upon addition of kaolinite into oxide mixture, the temperature required to produce chromatite shifts to 1000 °C with a remarkable reduction in the fraction of Cr(6+). Beyond 1000 °C, transient phases are formed that bear Cr in intermediate valence states, which convert to different species other than Cr(6+) in the cooling stage; (3) of significance to Cr mobility from the waste products generated by combustion, chromatite formed at1000 °C has a glassy disposition that prevents its water-based leaching; and (4) Increasing temperature facilitates the migration of eskolaite particles into bulk lime and enhances the extent to which Cr(3+) is oxidized, thereby completing the oxidation of Cr(3+) to Cr(6+) within 10 min.

Sodium-ion batteries are the next-generation in battery technology; however, their commercial development is hampered by electrode performance. The P2-type Na2/3(Fe1/2Mn1/2)O2 with a hexagonal structure and P63/mmc space group is considered a candidate sodium-ion battery cathode material due to its high capacity (∼190 mAh·g–1) and energy density (∼520 mWh·g–1), which are comparable to those of the commercial LiFePO4 and LiMn2O4 lithium-ion battery cathodes, with previously unexplained poor cycling performance being the major barrier to its commercial application. We use operando synchrotron X-ray powder diffraction to understand the origins of the capacity fade of the Na2/3(Fe1/2Mn1/2)O2 material during cycling over the relatively wide 1.5–4.2 V (vs Na) window. We found a complex phase-evolution, involving transitions from P63/mmc (P2-type at the open-circuit voltage) to P63 (OP4-type when fully charged) to P63/mmc (P2-type at 3.4–2.0 V) to Cmcm (P2-type at 2.0–1.5 V) symmetry structures during the desodi...

This paper describes the quantitative measurement, byin situsynchrotron X-ray diffraction (S-XRD) and subsequent Rietveld-based quantitative phase analysis and thickness calculations, of the evolution of the PbO2and PbSO4surface layers formed on a pure lead anode under simulated copper electrowinning conditions in a 1.6 MH2SO4electrolyte at 318 K. This is the first report of a trulyin situS-XRD study of the surface layer evolution on a Pb substrate under cycles of galvanostatic and power interruption conditions, of key interest to the mining, solvent extraction and lead acid battery communities. The design of a novel reflection geometry electrochemical flow cell is also described. Thein situS-XRD results show that β-PbO2forms immediately on the anode under galvanostatic conditions, and undergoes continued growth until power interruption where it transforms to PbSO4. The kinetics of the β-PbO2to PbSO4conversion decrease as the number of cycles increases, whilst the amount of residual PbO2increases with the number of cycles due to incomplete conversion to PbSO4. Conversely, complete transformation of PbSO4to β-PbO2was observed in each cycle. The results of layer thickness calculations demonstrate a significant volume change upon PbSO4to β-PbO2transformation.

The formation and decomposition of silico-ferrite of calcium and aluminium (SFCA) and SFCA-I iron ore sinter bonding phases have been investigated usingin situsynchrotron and laboratory X-ray diffraction (XRD) and neutron diffraction (ND). An external standard approach for determining absolute phase concentrations via Rietveld refinement-based quantitative phase analysis is discussed. The complementarity ofin situXRD and ND in characterising sinter phase formation and decomposition is also shown, with the volume diffraction afforded by the neutron technique reducing errors in the quantification of magnetite above ~1200 °C. Finally, by collecting 6 s laboratory XRD datasets and using a heating rate of 175 °C min−1, phase formation and decomposition have been monitored under heating rates more closely approximating those encountered in industrial iron ore sintering.

The wide ranging magnetic behavior in intermetallic compounds continues to attract broad interest. Effective control of their magnetic properties is of great importance for fundamental research and potential applications. In this work the structural and magnetic properties of $\mathrm{TbC}{\mathrm{o}}_{2}\mathrm{M}{\mathrm{n}}_{x}$ compounds are studied by a combination of temperature dependent synchrotron x-ray diffraction, neutron powder diffraction, specific heat, and magnetic measurements. Magnetization measurements show that the addition of Mn can modify the magnetic behavior significantly: first, the magnetic transition temperatures increase from \ensuremath{\sim}227 K to 332 K with $x=0.0\phantom{\rule{0.28em}{0ex}}\mathrm{to}\phantom{\rule{0.28em}{0ex}}0.3$; secondly, the nature of the magnetic transitions change from the first order to second order, as identified by three methods (Banerjee criterion, master curves of magnetic entropy changes, and detailed crystal structure analysis through neutron diffraction). Both synchrotron x-ray diffraction and neutron diffraction confirm that a structural transition, from cubic $Fd\overline{3}m$ to rhombohedral $R\overline{3}m$ on cooling, occurred accompanying the magnetic transition. To further clarify the nature of the second order magnetic phase transitions, we have carried out a detailed critical exponent analysis. The derived critical exponents are close to the theoretical prediction from the mean-field model, indicating the magnetic interactions are long range. This work benefits our general understanding of magnetic interactions in intermetallic compounds and provides guidance to design a functional magnetic material for room temperature magnetic devices.

The structure of TcO

We have investigated $\mathrm{DyMn}\phantom{\rule{0.16em}{0ex}}^{16}\mathrm{O}_{3}$ and its isotopically substituted counterpart $\mathrm{DyMn}\phantom{\rule{0.16em}{0ex}}^{18}\mathrm{O}_{3}$ by neutron powder diffraction, x-ray diffraction, and heat capacity measurements to investigate the mechanism leading to its magnetically induced electric polarization. $^{18}\mathrm{O}$ isotope substitution does not influence the magnetic ordering temperature of the Mn ions ${T}_{\mathrm{N},\mathrm{Mn}}$ or the multiferroic ordering temperature ${T}_{\mathrm{l}}$ coinciding with the onset of the spin spiral phase; however, it does reduce the ordering temperature of Dy into its incommensurate magnetic state ${T}_{\mathrm{N},\mathrm{Dy}}$ from 7.0(1) K to 5.9(1) K. The temperature dependence of the magnetic propagation vector, ${\mathbf{q}}_{\mathrm{IC}}$, changes with $^{18}\mathrm{O}$ substitution, while ${T}_{\mathrm{l}}$ remains almost constant, independent of ${\mathbf{q}}_{\mathrm{IC}}$. Pronounced changes in the lattice parameters occur at the various phase transitions. Furthermore, distinct subpicometer-scale distortions of the $\mathrm{Mn}{\mathrm{O}}_{6}$ octahedra and displacements of the Dy ions are observed below the ferroelectric phase transition at ${T}_{\mathrm{l}}$ in both samples, pointing toward the mechanism for electric polarization and its coupling to the orbital degrees of freedom.

The structural and magnetic properties of the two Ir(V) perovskites Ba2ScIrO6 and Sr2ScIrO6 have been established. The structures were refined using a combined neutron and Synchrotron data set. At room temperature the former has a cubic structure in space group Fm3 ̅m a = 8.1450(3) Å and the latter is monoclinic in P21/n with a = 5.6606(3) b= 5.6366(3) c = 7.9720(4) Å β = 89.977(5)°. Magnetization measurements show both oxides have magnetic moments close to zero as a consequence of strong spin-orbit coupling that results in a Jeff ~ 0 ground state. The distortion of the IrO6 octahedra in Sr2ScIrO6 is insufficient to generate crystal field splitting strong enough to quench the spin orbit coupling. Australian Synchrotron Australian Research Council

In situ heating, synchrotron radiation X-ray diffraction has been used to study the alloying and phase transformation behavior of TiH2-6Al-4V and Ti-6Al-4V alloys. Accelerated alloying and phase transformation were observed in the powder compact of the TiH2-6Al-4V alloy subjected to a high heating rate. In addition, an oxygen-stabilized Ti4Fe2O phase, which is present as sub-micron or nanoscaled particles, has been identified in the TiH2-6Al-4V alloy. The implications of these experimental findings have been discussed in terms of alloying, improved densification and oxygen scavenging in titanium and titanium alloys.

The incorporation of uranium into gadolinium zirconate (Gd2Zr2O7) is investigated by synchrotron X-ray powder diffraction and X-ray absorption near-edge structure (XANES) spectroscopy. The results suggest that the uranium cation is largely located on the pyrochlore B-site instead of the targeted A-site. Cation disorder in Gd2Zr2O7 and U-doped Gd2Zr2O7 is investigated by positron annihilation lifetime spectroscopy (PALS) which demonstrates the absence of cation vacancies in these systems. This work provides direct evidence for cation antisite (A- and B-site mixing) disorder in U-doped and off-stoichiometric Gd2Zr2O7 pyrochlore.

Effects of basicity, B (CaO:SiO2 ratio) on the thermal range, concentration, and formation mechanisms of silico-ferrite of calcium and aluminum (SFCA) and SFCA-I iron ore sinter bonding phases have been investigated using an in situ synchrotron X-ray diffraction-based methodology with subsequent Rietveld refinement-based quantitative phase analysis. SFCA and SFCA-I phases are the key bonding materials in iron ore sinter, and improved understanding of the effects of processing parameters such as basicity on their formation and decomposition may assist in improving efficiency of industrial iron ore sintering operations. Increasing basicity significantly increased the thermal range of SFCA-I, from 1363 K to 1533 K (1090 °C to 1260 °C) for a mixture with B = 2.48, to ~1339 K to 1535 K (1066 °C to 1262 °C) for a mixture with B = 3.96, and to ~1323 K to 1593 K (1050 °C to 1320 °C) at B = 4.94. Increasing basicity also increased the amount of SFCA-I formed, from 18 wt pct for the mixture with B = 2.48 to 25 wt pct for the B = 4.94 mixture. Higher basicity of the starting sinter mixture will, therefore, increase the amount of SFCA-I, considered to be more desirable of the two phases. Basicity did not appear to significantly influence the formation mechanism of SFCA-I. It did, however, affect the formation mechanism of SFCA, with the decomposition of SFCA-I coinciding with the formation of a significant amount of additional SFCA in the B = 2.48 and 3.96 mixtures but only a minor amount in the highest basicity mixture. In situ neutron diffraction enabled characterization of the behavior of magnetite after melting of SFCA produced a magnetite plus melt phase assemblage.

A novel compound for carbon capture and storage (CCS) applications, the 6H perovskite Ba4Sb2O9, was found to be able to absorb CO2 through a chemical reaction at 873 K to form barium carbonate and BaSb2O6. This absorption was shown to be reversible through the regeneration of the original Ba4Sb2O9 material upon heating above 1223 K accompanied by the release of CO2. A combined synchrotron X-ray diffraction, thermogravimetric, and microscopy study was carried out to characterize first the physical absorption properties and then to analyze the structural evolution and formation of phases in situ. Importantly, through subsequent carbonation and regeneration of the material over 100 times, it was shown that the combined absorption and regeneration reactions proceed without any significant reduction in the CO2 absorption capacity of the material. After 100 cycles the capacity of Ba4Sb2O9 was ∼0.1 g (CO2)/g (sorbent), representing 73% of the total molar capacity. This is the first report of a perovskite-type ma...