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We have made the compound 2O-BaPtO 3 by high-pressure, high-temperature synthesis, determined its structure, and tested its catalytic activity. Compounds of the same stoichiometry have been reported and tentatively identified as hexagonal perovskites, and although no structural model was ever established, 2O-BaPtO 3 is clearly different and, to the best of our knowledge, unique. It features continuous chains of face-sharing PtO 6 octahedra, like the well-known 2H hexagonal perovskite type, but with a staggered offset between the chains that breaks hexagonal symmetry and disrupts the close-packed array of A = Ba and X = O that is a defining characteristic of ABX 3 perovskites. We investigated this structure and its stability vs the conventional 2H form using X-ray and neutron diffraction, X-ray absorption spectroscopy, and ab initio calculations. Catalytic testing of 2O-BaPtO 3 showed that it is active for hydrogen evolution.

Oxygen-deficient perovskite compounds with the general formula Ba 3 R Fe 2 O 7.5 present a good opportunity to study competing magnetic interactions between Fe 3+ 3 d cations with and without the involvement of unpaired 4 f electrons on R 3+ cations. From analysis of neutron powder diffraction data, complemented by ab initio density functional theory calculations, we determined the magnetic ground states when R 3+ = Y 3+ (non-magnetic) and Dy 3+ (4 f 9 ). They both adopt complex long-range ordered antiferromagnetic structures below T N = 6.6 and 14.5 K, respectively, with the same magnetic space group C a 2/ c (BNS #15.91). However, the dominant influence of f-electron magnetism is clear in temperature dependence and differences between the size of the ordered moments on the two crystallographically independent Fe sites, one of which is enhanced by R -O-Fe superexchange in the Dy compound, while the other is frustrated by it. The Dy compound also shows evidence for temperature- and field-dependent transitions with hysteresis, indicating a field-induced ferromagnetic component below T N .

We demonstrate a modular synthesis approach to yield mesoporous carbon-coated anatase (denoted as TiO 2 /C) nanostructures. Combining polymerization-induced self-assembly (PISA) and reversible addition-fragmentation chain-transfer (RAFT) dispersion polymerization enabled the fabrication of uniform core-shell polymeric nanoreactors with tunable morphologies. The nanoreactors comprised of a poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) shell and a poly(benzyl methacrylate) (PBzMA) core. We selected worm-like and vesicular morphologies to guide the nanostructuring of a TiO 2 precursor, namely, titanium(IV) bis (ammonium lactato)dihydroxide (TALH). Subsequent carbonization yielded nanocrystalline anatase and simultaneously introduced a porous carbon framework, which also suppressed the crystal growth (∼5 nm crystallites). The as-prepared TiO 2 /C materials comprised of a porous structure, with large specific surface areas (>85 m 2 /g) and various carbon contents (20-30 wt %). As anode components in lithium-ion batteries, our TiO 2 /C nanomaterials improved the cycling stability, facilitated high overall capacities, and minimized the capacity loss compared to both their sans carbon and commercial anatase analogues.

We positively identified and quantified the solid-state phases involved in the carbonation/decarbonation cycle of Na 2 ZrO 3 when used for carbon capture. Previous work had only qualitatively inferred the phases present using diffraction pattern matching and thermogravimetric analysis. Here, we used the Rietveld-refinement method to analyze synchrotron X-ray and neutron powder diffraction data from samples treated ex situ . We then confirmed and extended our findings by in situ diffraction using a purpose-built gas-flow apparatus. This allowed us to resolve discrepancies in the earlier literature concerning which phases are present during the carbonation and regeneration processes. A key finding is the simultaneous presence of the monoclinic and tetragonal phases of ZrO 2 and that the "metastable" tetragonal phase is favored by smaller particles and can reincorporate into the bulk but the stable monoclinic phase does not. The result will help optimize the cycling of Na 2 ZrO 3 .

The crystal and magnetic structures and properties of the monoclinic form of the iron hydroxysulfate FeOHSO 4 were investigated by magnetometry and neutron powder diffraction. The space group C 2/ c was confirmed, and the proton position was located close to that predicted by ab initio calculations. The collinear antiferromagnetic k (0,0,0) structure forming below the Néel temperature T N ∼ 125 K is described by the C 2'/ c ' (No. 15.89) magnetic space group, with the moments along the b axis. Overall, FeOHSO 4 is isostructural to FeSO 4 F in terms of both the crystal and magnetic structures.

Decoupling the roles of the farnesoid X nuclear receptor and Takeda G-protein-coupled bile acid receptor 5 is essential for the development of novel bile acid therapeutics targeting metabolic and neurodegenerative diseases. Herein, we describe the synthesis of 12β-methyl-18- nor -bile acids which may serve as probes in the search for new bile acid analogues with clinical applicability. A Nametkin-type rearrangement was applied to protected cholic acid derivatives, giving rise to tetra-substituted Δ 13,14 - and Δ 13,17 -unsaturated 12β-methyl-18- nor -bile acid intermediates ( 24a and 25a ). Subsequent catalytic hydrogenation and deprotection yielded 12β-methyl-18- nor -chenodeoxycholic acid ( 27a ) and its 17- epi -epimer ( 28a ) as the two major reaction products. Optimization of the synthetic sequence enabled a chromatography-free route to prepare these bile acids at a multi-gram scale. In addition, the first cis -C-D ring-junctured bile acid and a new 14(13 → 12)- abeo -bile acid are described. Furthermore, deuteration experiments were performed to provide mechanistic insights into the formation of the formal anti-hydrogenation product 12β-methyl-18- nor -chenodeoxycholic acid ( 27a )., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

Na 2 O 2 is one of the possible discharge products from sodium-air batteries. Here, we report the evolution of the structure of Na 2 O 2 from room temperature to 500 °C using variable-temperature neutron and synchrotron X-ray powder diffraction. A phase transition from α-Na 2 O 2 to β-Na 2 O 2 is observed in the neutron diffraction measurements above 400 °C, and the crystal structure of β-Na 2 O 2 is determined from neutron diffraction data at 500 °C. α-Na 2 O 2 adapts a hexagonal P 62 m (no. 189) structure, and β-Na 2 O 2 adapts a tetragonal I 4 1 / acd (no. 142) structure. The thermal expansion coefficients of α-Na 2 O 2 are a = 2.98(1) × 10 -5 K -1 , c = 2.89(1) × 10 -5 K -1 , and V = 8.96(1) × 10 -5 K -1 up to 400 °C, and a ∼10% volume expansion occurs during the phase transition from α-Na 2 O 2 to β-Na 2 O 2 due to the realignment/rotation of O 2 2- groups. Both phases are electronic insulators according to DFT calculations with band gaps (both indirect) of 1.75 eV (α-Na 2 O 2 ) and 2.56 eV (β-Na 2 O 2 ). An impedance analysis from room temperature to 400 °C revealed a significant enhancement of the conductivity at T ≥ 275 °C. α-Na 2 O 2 shows a higher conductivity (∼10 times at T ≤ 275 °C and ∼3 times at T > 275 °C) in O 2 compared to in Ar. We confirmed, by dielectric analysis, that this enhanced conductivity is dominated by ionic conduction.

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 0.7 MnO 2 solid state synthesized at 1000 °C that shows two distinct phases; one adopts hexagonal P2-type P 6 3 / mmc space group symmetry, and the other adopts orthorhombic Pbma space group symmetry. The phase ratio of P2 to the orthorhombic phase is 55.0(5):45.0(4). A single-phase P2 structure is found to form at 1000 °C after modification with alkali metals Rb and Cs, while the K-modified form produces an additional minor impurity. The modification is the addition of the alkali elements during synthesis that do not appear to be doped into the crystal structure. As a cathode for NIBs, parent Na 0.7 MnO 2 shows a second charge/discharge capacity of 143/134 mAh g -1 , K-modified Na 0.7 MnO 2 a capacity of 184/178 mAh g -1 , Rb-modified Na 0.9 MnO 2 a capacity of 159/150 mAh g -1 , and Cs-modified Na 0.7 MnO 2 a capacity of 171/163 mAh g -1 between 1.5 and 4.2 V at a current density of 15 mA g -1 . The parent Na 0.7 MnO 2 is compared with alkali metal (K, Rb, and Cs)-modified Na x MnO 2 in terms of surface morphology using scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy, scanning electron microscopy, 23 Na solid-state nuclear magnetic resonance, and X-ray photoelectron spectroscopy and in terms of electrochemical performance and structural electrochemical evolution using in situ or operando synchrotron X-ray diffraction.

In this work, a latent energy-transfer process in traditional Eu 3+ ,Tb 3+ -doped phosphors is proposed and a new class of Eu 3+ ,Tb 3+ -doped Na 4 CaSi 3 O 9 (NCSO) phosphors is presented which is enabled by luminescence decay dynamics that optimize the electron-transfer energy process. Relative to other Eu 3+ ,Tb 3+ -doped phosphors, the as-synthesized Eu 3+ ,Tb 3+ -doped NCSO phosphors show improved large-scale tunable emission color from green to red upon UV excitation, controlled by the Tb 3+ /Eu 3+ doping ratio. Detailed spectroscopic measurements in the vacuum ultraviolet (VUV)/UV/Vis region were used to determine the Eu 3+ -O 2- charge-transfer energy, 4f-5d transition energies, and the energies of 4f excited multiplets of Eu 3+ and Tb 3+ with different 4f N electronic configurations. The Tb 3+ →Eu 3+ energy-transfer pathway in the co-doped sample was systematically investigated, by employing luminescence decay dynamics analysis to elucidate the relevant energy-transfer mechanism in combination with the appropriate model simulation. To demonstrate their application potential, a prototype white-light-emitting diode (WLED) device was successfully fabricated by using the yellow luminescence NCSO:0.03Tb 3+ , 0.05Eu 3+ phosphor with high thermal stability and a BaMgAl 10 O 17 :Eu 2+ phosphor in combination with a near-UV chip. These findings open up a new avenue to realize and develop multifunctional high-performance phosphors by manipulating the energy-transfer process for practical applications., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The synergistic incorporation of anatase TiO 2 domains into siliceous TUD-1 was optimized in this work and the resulting sample was implemented as the electrode in lithium-ion batteries. Triethanolamine was used as both the templating and complexing agent, the Si/Ti ratio was controlled, and the formation of Ti-O-Si bridges was optimized, as revealed through Fourier transform infrared spectroscopy, with the porous character of the materials being confirmed with N 2 adsorption-desorption isotherms. The controlled formation of Ti-O-Si bridges resulted in attractive specific charge capacities, high rate capability, and a good retention of capacity. The electrochemical performance of the composite material clearly demonstrates a synergistic effect between pure TiO 2 in its anatase form and the otherwise inactive siliceous TUD-1 matrix. Specific capacities of 300 mA h g -1 with a retention of 94% were obtained at a current density of 0.1 A g -1 over 100 cycles. This work showcases the use of bifunctional templating agents in the improvement of the performance and the long-term cyclability of composite electrodes, which can be potentially applied in future synthesis of energy materials., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

A 2-D coordination framework, (NEt 4 ) 2 [Fe 2 (fan) 3 ] ( 1·5(acetone) ; H 2 fan = 3,6-difluoro-2,5-dihydroxy-1,4-benzoquinone), was synthesized and structurally characterized. The compound is structurally analogous to a formerly elucidated framework, (NEt 4 ) 2 [Fe 2 (can) 3 ] (H 2 can = 3,6-dichloro-2,5-dihydroxy-1,4-benzoquinone), and adopts a 2-D (6,3) topology with the symmetrical stacking of [Fe 2 (fan) 3 ] 2- sheets that are held in position by the NEt 4 + cations between the sheets. The investigation of the dc and ac magnetic properties of 1·5(acetone) revealed ferromagnetic ordering behavior and slow magnetization relaxation, as evinced from ac susceptibility measurements. Furthermore, the exposure of 1·5(acetone) to air led to the formation of a heptahydrate 1·7H 2 O which displayed distinct magnetic properties. The study of the redox state and extent of delocalization in 1·5(acetone) was undertaken via crystallography, in combination with Mössbauer and vis-NIR spectroscopy, to reveal the mixed-valence and delocalized nature of the as-synthesized material. As a result, the conductivity studies conducted on a pressed pellet showed a relatively high conductivity of 1.8 × 10 -2 S cm -1 (300 K). In order to compare structurally related anilate-based structures, a relationship among the redox state, spectroscopic properties, and electronic properties was elucidated in this work. A preliminary investigation of 1·5(acetone) as a candidate anode material in lithium ion batteries revealed a high reversible capacity of 676.6 mAh g -1 and high capacity retention.

Li 3 Co 2 SbO 6 is found to adopt two highly distinct structural forms: a pseudohexagonal (monoclinic C 2/ m ) layered O3-LiCoO 2 type phase with "honeycomb" 2:1 ordering of Co and Sb, and an orthorhombic Fddd phase, isostructural with Li 3 Co 2 TaO 6 but with the addition of significant Li/Co ordering. Pure samples of both phases can be obtained by conventional solid-state synthesis via a precursor route using Li 3 SbO 4 and CoO, by controlling particle size, initial lithium excess, and reaction time. Both phases show relatively poor performance as lithium-ion battery cathode materials in their as-made states, but complex and interesting low-temperature magnetic properties. The honeycomb phase is the first of its type to show A-type antiferromagnetic order (ferromagnetic planes, antiferromagnetically coupled) below T N = 14 K. Isothermal magnetization and in-field neutron diffraction below T N show clear evidence for a metamagnetic transition at H ≈ 0.7 T to three-dimensional ferromagnetic order. The orthorhombic phase orders antiferromagnetically below T N = 112 K and then undergoes two more transitions at 80 and 60 K. Neutron diffraction data show that the ground state is incommensurate.

The room-temperature structure of brownmillerite-type Sr 2 Fe 2 O 5 remains controversial, despite numerous published crystallographic studies utilizing X-ray, neutron, and electron diffraction data collected on single-crystalline and powder samples. The main disagreements concern the ordering of twisted FeO 4 tetrahedral chains within and between the layers stacked along the b axis, and the impact of this ordering on oxide-ionic conductivity. Here, we present new data along with a reinterpretation of previously published diffraction images, including the reassignment of satellite reflections, which harmonize the results of past studies in a unified description of tetrahedral chain ordering in Sr 2 Fe 2 O 5 at length scales relevant to X-ray and neutron diffraction. Implications for the prevailing model of oxide ion transport in this material are also discussed.

We design a facile approach to prepare a bimetallic transition-metal-sulphide-based 3D hierarchically-ordered porous electrode based on bimetallic metal-organic frameworks (Ni-Co-MOFs) by using confinement growth and in-situ sulphurisation techniques. In the novel resulting architectures, Ni-Co-S nanoparticles are confined in bowknot-like and flower-like carbon networks and are mechanically isolated but electronically well-connected, where the carbon networks with a honeycomb-like feature facilitate electron transfer with uninterrupted conductive channels from all sides. Moreover, these hierarchically-ordered porous structures together with internal voids can accommodate the volume expansion of the embedded Ni-Co-S nanoparticles. The pseudocapacitive behaviours displayed in the NCS@CBs and NCS@CFs occupied a significant portion in the redox processes. Because of these merits, both the as-built bowknot and flower networks show excellent electrochemical properties for lithium storage with superior rate capability and robust cycling stability (994 mAh g -1 for NCS@CBs and 888 mAh g -1 for NCS@CFs after 200 cycles). This unique 3D hierarchically-ordered structural design is believed to hold great potential applications in propagable preparation of carbon networks teamed up with sulphide nanocrystals for high energy storage.

Melilite-type Ba 2 MnSi 2 O 7 was synthesized by a standard powder solid-state reaction route, and its magnetic properties were studied at low temperature. The magnetic structure was found to be C-type pointing along the c axis from neutron powder diffraction, which is different from the G-type ordering previously reported in all other 2-2-4-2 melilites with manganese as the B'-site transition metal. Ab initio (density functional theory) and magnetic dipole-dipole calculations were used to understand the magnetic structure by determining the spin supersuperexchange parameters as well as the relative influence of spin-orbit coupling and the magnetic dipole-dipole interactions.

Having identified a set of conditions that predispose a solid-state ionic compound to a pressure-induced valence transition, we investigated a series of Bi(iii) perovskite oxides. We found such a transition below 10 GPa in every case, including one that we synthesised for the first time (double perovskite-type Ba2BiOsO6).

This work demonstrates that simple copper-bipyridine compounds and atmospheric CO2 react to produce useful/complex materials under appropriate conditions. Starting from a distorted square planar copper(ii) complex, [(tbubpy)CuCl2](tbubpy = 4-tert-butyl-2-(4-tert-butylpyridin-2-yl)pyridine), an air-sensitive, copper(i) complex, [(tbubpy)2CuI][BF4], which exhibits a distorted tetrahedral geometry, was synthesized and characterized. Reactions of [(tbubpy)2CuI][BF4] with CO2 inside a sealed tube and with air were carried out over a week and three weeks, respectively. A new tricopper(ii)-carbonato cluster, [{(tbubpy)2Cu}3(μ-CO3)][PF6]4, was isolated with three distorted octahedral copper(ii) centres bound by a carbonate-bridge formed from atmospheric CO2. NMR and UV-Vis spectroscopic analyses coupled with previous reports point to a multi-step process in the formation of a trinuclear CuII-carbonato cluster that includes the probable involvement of μ-hydroxo-bridged dicopper(ii) type intermediates.

Understanding the short-range molecular motions of organic ionic plastic crystals is critical for the application of these materials as solid-state electrolytes in electrochemical devices such as lithium batteries. However, the theory of short-range-motions was originally developed for simple molecular plastic crystals and does not take account of strong interionic interactions that are present in organic ionic plastic crystals. Here we report a fundamental investigation of the dynamic behavior of an archetypal example triethyl(methyl)phosphonium bis(fluorosulfonyl)amide ([P 1222 ][FSI]) through calorimetry, impedance spectroscopy, synchrotron X-ray diffraction, and solid-state NMR and Raman spectroscopies. For the first time, we show the presence of conformational dynamics in the solid state for the FSI anion. We relate the dynamics to a unique second-order displacive phase transition of [P 1222 ][FSI]. This detailed analysis suggests a new disorder mechanism involving cooperative motion between the cation and FSI anion in the plastic crystal due to strong interionic interactions.

Polycrystalline samples in the solid solution ZrMn 2-x Co x Ge 4 O 12 (x = 0.0, 0.5, 1.0, 1.5 and 2.0) have been prepared using the ceramic method and characterised by a combination of magnetometry, X-ray diffraction and neutron diffraction. They all adopt the space group P4/nbm with a ∼ 9.60, c ∼ 4.82 Å and show long-range magnetic order with transition temperatures, T C , in the range 2 ≤ T C /K ≤ 10. The underlying magnetic structure is the same in each case but the ordered spins lie along [001] when x = 0.0 and in the (001) plane for all other compositions. In all cases the magnetically-ordered phase is a weak ferromagnet although the magnitude of the spontaneous magnetisation and the strength of the coercive field are composition-dependent. The magnetic structure can be rationalized by considering the strengths of the interactions along the distinct M-O-Ge-O-M superexchange pathways in the crystal and the observed magnetic structure is entirely consistent with the predictions of ab initio calculations.

Twisted-melilite dipotassium cobalt pyrophosphate (K 2 CoP 2 O 7 , P4 2 /mnm, #136), originally reported by Gabelica-Robert (1981), was synthesized in powder form by a standard solid-state reaction route. The magnetic properties of the material were studied by magnetometry and its magnetic structure determined using neutron powder diffraction for the first time. Below T N = 11 K, the material adopts a G-type antiferromagnetic structure with moments aligned in the ab-plane (magnetic space group Pn'nm, #58.3.473). Ab initio calculations were performed to examine the isotropic magnetic spin exchange parameters as well as the preferred direction of magnetic moments due to spin-orbit coupling. The relationship between crystal structure geometry and the strength of the magnetic interactions was examined and compared to those of melilite-type Sr 2 CoGe 2 O 7 .

We report a new gaudefroyite-type compound YCa3(CrO)3(BO3)4, in which Cr(3+) ions (3d(3), S = 3/2) form an undistorted kagomé lattice. Using a flux agent, the synthesis was significantly accelerated with the typical calcining time reduced from more than 2 weeks to 2 d. The structure of YCa3(CrO)3(BO3)4 was determined by combined Rietveld refinements against X-ray and neutron diffraction data. Symmetry distortion refinement starting from a disordered YCa3(MnO)3(BO3)4 model was applied to avoid overparameterization. There are two ordering models, namely, K2-1 and K2-2, with the space groups P63 (No. 173) and P3̅ (No. 147), respectively, that differ in the [BO3] ordering between different channels (in-phase or out-of-phase). Both models give similarly good fits to the diffraction data. YCa3(CrO)3(BO3)4 is an insulator with the major band gap at Eg = 1.65 eV and a second transition at 1.78 eV. Magnetically, YCa3(CrO)3(BO3)4 is dominated by anti-ferromagnetic exchange along edge-sharing CrO6 octahedral chains perpendicular to the kagomé planes, with Θ ≈ -120 K and μeff ≈ 3.92 μB. The compound shows no spin ordering or freezing down to at least 2 K.

Phonons in condensed matter materials transmit energy through atomic lattices as coherent vibrational waves. Like electronic and photonic properties, an improved understanding of phononic properties is essential for the development of functional materials, including thermoelectric materials. Recently, an Einstein rattling mode was found in thermoelectric material Na0.8CoO2, due to the large displacement of Na between the [CoO2] layers. In this work, we have realized a different type of rattler in another thermoelectric material Ca3Co4O9 by chemical doping, which possesses the same [CoO2] layer as Na0.8CoO2. It remarkably suppressed the thermal conductivity while enhancing its electrical conductivity. This new type of rattler was investigated by inelastic neutron scattering experiments in conjunction with ab-initio molecular dynamics simulations. We found that the large mass of dopant rather than the large displacement is responsible for such rattling in present study, which is fundamentally different from skutterudites, clathrates as well as Na analogue. We have also tentatively studied the phonon band structure of this material by DFT lattice dynamics simulation, showing the relative contribution to phonons in the distinct layers of Ca3Co4O9.

Fe4Si2Sn7O16 has a unique crystal structure that contains alternating layers of Fe(2+) ions octahedrally coordinated by O (oxide layer) and Sn (stannide layer), bridged by SiO4 tetrahedra. The formula can be written as FeFe3Si2Sn7O16 to emphasise the distinction between the layers. Here, we report the changes in structure and properties as iron is selectively replaced by manganese in the oxide layer. Solid-state synthesis was used to produce polycrystalline samples of Fe(Fe3-xMnx)Si2Sn7O16 for x≤ 2.55, the structures of which were characterised using high-resolution synchrotron X-ray and neutron powder diffraction. Single-crystal samples were also grown at x = 0.35, 0.95, 2.60 and characterised by single crystal X-ray diffraction. We show that manganese is doped exclusively into the oxide layer, and that this layer contains exclusively magnetically active high-spin M(2+) transition metal cations; while the stannide layer only accommodates non-magnetic low-spin Fe(2+). All samples show clear evidence of geometrically frustrated magnetism, which we associate with the fact that the topology of the high-spin M(2+) ions in the oxide layer describes a perfect kagomé lattice. Despite this frustration, the x = 0 and x = 2.55 samples undergo long-range antiferromagnetic ordering transitions at 3.0 K and 2.5 K, respectively.

The hexagonal perovskites Ba3BiIr2O9, Ba3BiRu2O9, and Ba4BiIr3O12 all undergo pressure-induced 1% volume collapses above 5 GPa. These first-order transitions have been ascribed to internal transfer of valence electrons between bismuth and iridium/ruthenium, which is driven by external applied pressure because the reduction in volume achieved by emptying the 6s shell of bismuth upon oxidation to Bi(5+) is greater in magnitude than the increase in volume by reducing iridium or ruthenium. Here, we report direct observation of these valence transfers for the first time, using high-pressure X-ray absorption near-edge spectroscopy (XANES) measurements. Our data also support the highly unusual "4+" nominal oxidation state of bismuth in these compounds, although the possibility of local disproportionation into Bi(3+)/Bi(5+) cannot be definitively ruled out. Ab initio calculations reproduce the transition, support its interpretation as a valence electron transfer from Bi to Ir/Ru, and suggest that the high-pressure phase may show metallic behavior (in contrast to the insulating ambient-pressure phase).

Exploring future cathode materials for sodium-ion batteries, alluaudite class of Na2Fe(II)2(SO4)3 has been recently unveiled as a 3.8 V positive insertion candidate (Barpanda et al. Nat. Commun. 2014, 5, 4358). It forms an Fe-based polyanionic compound delivering the highest Fe-redox potential along with excellent rate kinetics and reversibility. However, like all known SO4-based insertion materials, its synthesis is cumbersome that warrants careful processing avoiding any aqueous exposure. Here, an alternate low temperature ionothermal synthesis has been described to produce the alluaudite Na2+2xFe(II)2-x(SO4)3. It marks the first demonstration of solvothermal synthesis of alluaudite Na2+2xM(II)2-x(SO4)3 (M = 3d metals) family of cathodes. Unlike classical solid-state route, this solvothermal route favors sustainable synthesis of homogeneous nanostructured alluaudite products at only 300 °C, the lowest temperature value until date. The current work reports the synthetic aspects of pristine and modified ionothermal synthesis of Na2+2xFe(II)2-x(SO4)3 having tunable size (300 nm ∼5 μm) and morphology. It shows antiferromagnetic ordering below 12 K. A reversible capacity in excess of 80 mAh/g was obtained with good rate kinetics and cycling stability over 50 cycles. Using a synergistic approach combining experimental and ab initio DFT analysis, the structural, magnetic, electronic, and electrochemical properties and the structural limitation to extract full capacity have been described.

A new bismuth-containing layered perovskite of the Ruddlesden-Popper type, K(2.5)Bi(2.5)Ti4O13, has been prepared by solid-state synthesis. It has been shown to hydrate to form stoichiometric K(2.5)Bi(2.5)Ti4O13·H2O. Diffraction data show that the structure consists of a quadruple-stacked (n = 4) perovskite layer, with potassium ions occupying the rock salt layer and its next-nearest A site. The hydrated sample was shown to remove the offset between stacked perovskite layers relative to the dehydrated sample. Computational methods show that the hydrated phase consists of intact H2O molecules in a vertical "pillared" arrangement bridging across the interlayer space. Rotations of H2O molecules about the c axis were evident in molecular dynamic calculations, which increased in rotation angle with increasing temperature. In situ diffraction data for the dehydrated phase point to a broad structural phase transition from orthorhombic to tetragonal at ∼600 °C. The relative bismuth-rich composition in the perovskite block results in a higher transition temperature compared to related perovskite structures. Water makes a significant contribution to the dielectric constant, which disappears after dehydration.

The Type II phase in the Bi1 - xWxO1.5 + 1.5x system is shown to have a (3 + 3)-dimensional modulated δ-Bi2O3-related structure, in which the modulation vector ℇ `locks in' to a commensurate value of 1/3. The structure was refined in a 3 × 3 × 3 supercell against single-crystal Laue neutron diffraction data. Ab initio calculations were used to test and optimize the local structure of the oxygen sublattice around a single mixed Bi/W site. The underlying crystal chemistry was shown to be essentially the same as for the recently refined (3 + 3)-dimensional modulated structure of Type II Bi1 - xNbxO1.5 + x (Ling et al., 2013), based on a transition from fluorite-type to pyrochlore-type via the appearance of W4O18 `tetrahedra of octahedra' and chains of corner-sharing WO6 octahedra along 〈110〉F directions. The full range of occupancies on this mixed Bi/W site give a hypothetical solid-solution range bounded by Bi23W4O46.5 (x = 0.148) and Bi22W5O48 (x = 0.185), consistent with previous reports and with our own synthetic and analytical results.

For structures that can be treated as networks of rigid, corner-connected polyhedra, the dominant distortion modes can be described by so-called rigid unit modes that are close to zero frequency. This type of behaviour is common in zeolitic/zeotypic materials such as the AlPO4 family of compounds and has been suggested by some authors to play a significant role in molecular diffusion within the pores of such compounds. We explore the energy and temperature dependence of these modes in AlPO4-5 using inelastic neutron scattering and heat capacity measurements. Ab initio based computational modelling is also used to assign the observed dynamic behaviour to rigid unit modes. We observe that these rigid unit modes persist down to very low temperatures and show no signs of freezing out.

Promotive voice is essential for improving team and organization performance. Yet in the current literature, less was known regarding the psychological reasons why people engage in promotive voice. Through the lens of social exchange, we proposed that employees who received support from colleagues may develop higher level of felt obligation for constructive change which leads to promotive voice. Analyses of multi-source data from 51 cross-functional sources (51 team supervisors and 162 employees) showed that employees' felt obligation for constructive change positively mediates the relationship between colleague support and promotive voice behavior. Moreover, the impact of colleague support on felt obligation for constructive change is stronger when there is a low level of subgroup formation in the team. Theoretical and practical implications of these findings are discussed.

The relaxor ferroelectric K(0.5)Bi(0.5)TiO(3) has been synthesised in a solid-solution series with K(0.5)Bi(0.5)ZrO(3), as K(0.5)Bi(0.5)Ti1-xZrxO(3). High-resolution synchrotron X-ray powder diffraction and X-ray absorption near edge structure spectroscopy were used to characterise the long-range average and local structural behaviour. Rietveld refinements against diffraction data show that a pseudocubic tetragonal region exists across the whole solid-solution series, with truly cubic symmetry only observed at x = 1 (pure KBZ). Variable-temperature diffraction data for x = 0 (pure KBT) showed a broad ferroelectric transition from tetragonal to cubic symmetry at approximately 683 K with a coexistence of both phases close to that temperature, accompanied by a marked volume contraction. Ti K-edge data showed that Zr doping has a minimal effect on Ti off-centering, and revealed no evidence for local clustering. Metal L-edges showed that Ti(4+) cations remain off-centered with increasing Zr content, while Zr(4+) cations approach a higher-symmetry coordination environment, most likely due to the increased size of the Zr atoms. Although there is a minimal effect on actual Ti-offsets, an effective dilution of these environments by Zr doping leads to a reduction in polar domains and a diminished ferroelectric response.

The structural properties of (Bi0.5Na0.5)Ti1-xZrxO3 (where 0 ≤ x ≤ 0.7) have been investigated using powder diffraction and X-ray absorption spectroscopy. Diffraction measurements on (Bi0.5Na0.5)TiO3 confirm that both monoclinic Cc and rhombohedral R3c phases are present at room temperature. Doping small amounts of Zr into the B site of (Bi0.5Na0.5)TiO3 initially stabilizes the rhombohedral phase before the orthorhombic Pnma phase begins to form at x = 0.5. Analysis of the Ti K-edge and Zr L3-edge XANES spectra show that the crystallographic phase change has very little effect on the local structure of Ti(4+)/Zr(4+) cations, suggesting that there is little change in the cation off-center displacement within the BO6 octahedra with each successive phase change.

Tc L3-edge XANES spectra have been collected on powder samples of SrTcO3 (octahedral Tc(4+)) and NH4TcO4 (tetrahedral Tc(7+)) immobilized in an epoxy resin. Features in the Tc L3-edge XANES spectra are compared with the pre-edge feature of the Tc K-edge as well as other 4d transition metal L3-edges. Evidence of crystal field splitting is obvious in the Tc L3-edge, which is sensitive to the coordination number and oxidation state of the Tc cation. The Tc L3 absorption edge energy difference between SrTcO3 (Tc(4+)) and NH4TcO4 (Tc(7+)) shows that the energy shift at the Tc L3-edge is an effective tool for studying changes in the oxidation states of technetium compounds. The Tc L3-edge spectra are compared with those obtained from Mo and Ru oxide standards with various oxidation states and coordination environments. Most importantly, fitting the Tc L3-edge to component peaks can provide direct evidence of crystal field splitting that cannot be obtained from the Tc K-edge.

We have experimentally investigated the effects of pressure on the magnetoelastic transitions associated with the opening of spin-gaps in Ba3BiIr2O9 and Ba3BiRu2O9. For both compounds, reducing the unit cell volume by either external physical and internal chemical pressure was found to reduce the temperature T(*) of the transition and, to a lesser extent, the magnitude of the associated negative thermal volume expansion. The results yield the latent heat associated with the transitions, -3.34(3) × 10(2) J mol(-1) for Ba3BiIr2O9 and -7.1(5) × 10(2) J mol(-1) for Ba3BiRu2O9. The transition in Ba3BiRu2O9 is significantly more robust than in Ba3BiIr2O9, requiring an order of magnitude higher pressures to achieve the same reduction in T(*). The differing responses of the two compounds points to differences between the 4d and 5d metals and hence to the importance of spin-orbit coupling, which is expected to be much stronger in the Ir compound.

The structural, magnetic and electrical properties of the mixed Ti-Mn oxides Sr(1-x)La(x)Ti(0.5)Mn(0.5)O3 (0 ≤ x ≤ 0.5) are reported. At room temperature the oxides have a cubic structure in space group Pm3m for x ≤ 0.25 and rhombohedral in R3c for 0.3 ≤ x ≤ 0.50. X-ray absorption spectroscopic measurements demonstrate the addition of La(3+) is compensated by the partial reduction of Mn(4+) to Mn(3+). Variable temperature neutron diffraction measurements show that cooling Sr(0.6)La(0.4)Ti(0.5)Mn(0.5)O3 results in a first order transition from rhombohedra to an orthorhombic structure in Imma. Complex magnetic behaviour is observed. The magnetic behaviour of the mixed valent (Mn(3+/4+)) examples is dominated by ferromagnetic interactions, although cation disorder frustrates long range magnetic ordering.

Pressure-induced charge transfer from Bi to Ir/Ru is observed in the hexagonal perovskites Ba(3+n)BiM(2+n)O(9+3n) (n=0,1; M=Ir,Ru). These compounds show first-order, circa 1% volume contractions at room temperature above 5 GPa, which are due to the large reduction in the effective ionic radius of Bi when the 6s shell is emptied on oxidation, compared to the relatively negligible effect of reduction on the radii of Ir or Ru. They are the first such transitions involving 4d and 5d compounds, and they double the total number of cases known. Ab initio calculations suggest that magnetic interactions through very short (ca. 2.6 Å) M-M bonds contribute to the finely balanced nature of their electronic states., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The new compound LiNaMg[PO4]F has been synthesized by a wet chemical reaction route. Its crystal structure was determined from single-crystal X-ray diffraction data. LiNaMg[PO4]F crystallizes with the monoclinic pseudomerohedrally twinned LiNaNi[PO4]F structure, space group P2(1)/c, a = 6.772(4), b = 11.154(6), c = 5.021(3) Å, β = 90.00(1)° and Z = 4. The structure contains [MgO3F]n chains made up of zigzag edge-sharing MgO4F2 octahedra. These chains are interlinked by PO4 tetrahedra forming 2D-Mg[PO4]F layers. The alkali metal atoms are well ordered in between these layers over two atomic positions. The use of group-subgroup transformation schemes in the Bärnighausen formalism enabled us to determine precise phase transition mechanisms from LiNaNi[PO4]F- to Na2M[PO4]F-type structures (M = Mn-Ni, and Mg) (see video clip 1 and 2). The crystal and magnetic structure and properties of the parent LiNaNi[PO4]F phase were also studied by magnetometry and neutron powder diffraction. Despite the rather long interlayer distance, d(min)(Ni(+2)-Ni(+2)) ~ 6.8 Å, the material develops a long-range magnetic order below 5 K. The magnetic structure can be viewed as antiferromagnetically coupled ferromagnetic layers with moments parallel to the b-axis.

The magnetic structure and properties of sodium iron fluorophosphate Na2FePO4F (space group Pbcn), a cathode material for rechargeable batteries, were studied using magnetometry and neutron powder diffraction. The material, which can be described as a quasi-layered structure with zigzag Fe-octahedral chains, develops a long-range antiferromagnetic order below ∼3.4 K. The magnetic structure is rationalized as a super-exchange-driven ferromagnetic ordering of chains running along the a-axis, coupled antiferromagnetically by super-super-exchange via phosphate groups along the c-axis, with ordering along the b-axis likely due to the contribution of dipole-dipole interactions.

The key role played by bismuth in an average intermediate oxidation state in the magnetoelastic spin-gap compounds Ba3BiRu2O9 and Ba3BiIr2O9 has been confirmed by systematically replacing bismuth with La(3+) and Ce(4+). Through a combination of powder diffraction (neutron and synchrotron), X-ray absorption spectroscopy, and magnetic properties measurements, we show that Ru/Ir cations in Ba3BiRu2O9 and Ba3BiIr2O9 have oxidation states between +4 and +4.5, suggesting that Bi cations exist in an unusual average oxidation state intermediate between the conventional +3 and +5 states (which is confirmed by the Bi L3-edge spectrum of Ba3BiRu2O9). Precise measurements of lattice parameters from synchrotron diffraction are consistent with the presence of intermediate oxidation state bismuth cations throughout the doping ranges. We find that relatively small amounts of doping (∼10 at%) on the bismuth site suppress and then completely eliminate the sharp structural and magnetic transitions observed in pure Ba3BiRu2O9 and Ba3BiIr2O9, strongly suggesting that the unstable electronic state of bismuth plays a critical role in the behavior of these materials.

The title compounds were synthesized by a hydrothermal route from a 1:1 molar ratio of lithium fluoride and transition-metal acetate in an excess of water. The crystal structures were determined using a combination of powder and/or single-crystal X-ray and neutron powder diffraction (NPD) measurements. The magnetic structure and properties of Co(OH)F were characterized by magnetic susceptibility and low-temperature NPD measurements. M(OH)F (M = Fe and Co) crystallizes with structures related to diaspore-type α-AlOOH, with the Pnma space group, Z = 4, a = 10.471(3) Å, b = 3.2059(10) Å, and c = 4.6977(14) Å and a = 10.2753(3) Å, b = 3.11813(7) Å, and c = 4.68437(14) Å for the iron and cobalt phases, respectively. The structures consist of double chains of edge-sharing M(F,O)6 octahedra running along the b axis. These infinite chains share corners and give rise to channels. The protons are located in the channels and form O-H···F bent hydrogen bonds. The magnetic susceptibility indicates an antiferromagnetic ordering at ∼40 K, and the NPD measurements at 3 K show that the ferromagnetic rutile-type chains with spins parallel to the short b axis are antiferromagnetically coupled to each other, similarly to the magnetic structure of goethite α-FeOOH.

The crystal structure of the NaMnSO4F fluorosulfate phase prepared by low-temperature solid-state synthesis has been solved and refined by the Rietveld analysis of synchrotron X-ray powder diffraction data. Isostructural to the naturally occurring triplite family of minerals, this compound crystallizes in monoclinic C2/c symmetry (No. 15) with unit-cell parameters of a = 13.77027 (17), b = 6.63687 (8), c = 10.35113 (14) Å, β = 121.4795 (3)° and V = 806.78 (2) Å(3). Its structure is built of edge-sharing chains of distorted MO4F2 octahedra, which are interconnected by constituent SO4 tetrahedra to form a robust three-dimensional polyanionic framework. MO4F2 octahedra are randomly occupied by Na and Mn with close to 1:1 occupancy. This random mixing of cations among polyhedral building blocks means that there are no channels for Na-ion conduction, rendering it electrochemically inactive. The structure is discussed and compared with other known alkali metal fluorosulfates as well as to naturally occurring triplite-type minerals.

The 12L hexagonal perovskite Ba4BiIr3O12 has been synthesized for the first time and characterized using high-resolution neutron and synchrotron X-ray diffraction as well as physical properties measurements. The structure contains Ir3O12 linear face-sharing octahedral trimer units, bridged by corner-sharing BiO6 octahedra. The average electronic configurations of Ir and Bi are shown to be +4(d(5)) and +4(s(1)), respectively, the same as for the S = 1/2 dimer system Ba3BiIr2O9, which undergoes a spin-gap opening with a strong magnetoelastic effect at T* = 74 K. Anomalies in magnetic susceptibility, heat capacity, electrical resistivity, and unit cell parameters indeed reveal an analogous effect at T* ≈ 215 K in Ba4BiIr3O12. However, the transition is not accompanied by the opening of a gap in spin excitation spectrum, because antiferromagnetic coupling among S = 1/2 Ir(4+) (d(5)) cations leads to the formation of a S = 1/2 doublet within the trimers, vs S = 0 singlets within dimers. The change in magnetic state of the trimers at T* leads to a structural distortion, the energy of which is overcompensated for by the formation of S = 1/2 doublets. Extending this insight to the dimer system Ba3BiIr2O9 sheds new light on the more pronounced low-temperature anomalies observed for that compound.

The pyrochlore-defect fluorite phase transition in the mixed-metal zirconate Nd2-xYxZr2O7 (0 ≤ x ≤ 2) solid solution was investigated using synchrotron X-ray and neutron diffraction, as well as X-ray absorption spectroscopy. Diffraction analysis revealed a two-phase region between 1.0 ≤ x ≤ 1.2. In the pyrochlore phase, Zr L3-edge XANES analysis demonstrated a gradual change in the local coordination environment of the B site with increasing Y content that was consistent with an increase in disorder. Although Y L3-edge XANES analysis suggested that the Y cations remained in an ordered coordination environment in the pyrochlore phase, disorder did gradually increase once the fluorite phase formed. It was found that Y cations prefer an ordered coordination environment near the phase boundary whereas Zr cations prefer a disordered coordination environment.

The new compound MnF(2-x)(OH)x (x ~ 0.8) was synthesized by a hydrothermal route from a 1 : 1 molar ratio of lithium fluoride and manganese acetate in an excess of water. The crystal structure was determined using the combination of single crystal X-ray and neutron powder diffraction measurements. The magnetic properties of the title compound were characterized by magnetic susceptibility and low-temperature neutron powder diffraction measurements. MnF(2-x)(OH)x (x ~ 0.8) crystallizes with orthorhombic symmetry, space group Pnn2 (no. 34), a = 4.7127(18), b = 5.203(2), c = 3.2439(13) Å, V = 79.54(5) Å(3) and Z = 2. The crystal structure is a distorted rutile-type with [Mn(F,O)4] infinite edge-sharing chains along the c-direction. The protons are located in the channels and form O-HF bent hydrogen bonds. The magnetic susceptibility measurements indicate an antiferromagnetic ordering at ~70 K and the neutron powder diffraction measurements at 3 K show that the ferromagnetic chains with spins parallel to the c-axis are antiferromagnetically coupled to each other, similarly to the magnetic structure of tetragonal rutile-type MnF2 with isoelectronic Mn(2+). MnF(2-x)(OH)x (x ~ 0.8) is expected to be of great interest as a positive electrode for Li cells if the protons could be exchanged for lithium.