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International audience; Thanks to a homemade dynamic vacuum system, fully crystallized VO2 (M) is successfully synthesized in a merged step of vanadyl ethylene glycolate (VEG) decomposition and crystallization of VO2 at high temperatures (>500 °C). During the whole process, vanadium valence (+4) is well maintained, and VEG microstructure plays an important role in the end-product size and shape. Finally, the suggested route appears well suitable for the mass production of VO2 nanoparticles.

International audience; In this paper, a pyrolysis method is used to synthesize high quality VO2 powder. Black carbon and V2O5 powder are mixed and annealed at 650 °C or 800 °C under argon flow to initiate a carbo-reduction reaction. The 650 °C VO2 powder presents submicron particle size with an amorphous fraction estimated at 11.5%. With the increase of the annealing temperature up to 800 °C, grains become larger than the micron while the crystallinity goes up to 98.5% (i.e. amorphous fraction drops to 1.5%). This one-step process allows the preparation of quantities up to 10 g of VO2 powder and should be easily transferable to large-scale production. An innovative sintering process is then adopted to produce high quality thermochromic VO2 ceramics from the as-prepared VO2 powder. First, SPS process is used to obtain high-density VO2 pellet. Then, the VO2 pellet is post-annealed in a homemade induction furnace at 1300 °C under a controlled atmosphere to allow grain growth by coalescence and improve pellet surface quality. According to a surface topography analysis, the mean amplitude roughness parameter (Ra) of the obtained VO2 ceramic is found to be 2.93 ± 0.01 nm. A large resistance change by three orders of magnitude along the phase transition is observed, which makes the as-prepared smooth VO2 ceramic a promising candidate for various applications requiring optical and/or electronic switching behavior depending on temperature.

Thanks to a homemade dynamic vacuum system, fully crystallized VO

Vanadium dioxide (VO

International audience; Connected displays are the salient nature of our e-connected society requiring high-quality electronic conductive materials integrated in smart devices. Herein, we highlight the use of carbon nanotubes (CNTs) not only as substitutes for ITO (In2O3:Sn) but mainly as a counter electrode for electrochromic devices (ECDs). Using a dry spinning process, conductive CNT films with directionally oriented tubes were successfully laid on polyethylene terephthalate (PET) flexible substrates. The CNTs were synthesized as vertically aligned spinnable arrays by chemical vapor deposition. The transparency and optical absorption properties were tuned by adjusting the number of CNT layers (L) within the film from light gray for 1L to dark black above 10L. The CNT films, showing pseudo-capacitive to capacitive behavior in lithium-based electrolytes, were further integrated in ECDs based on poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) active layers. The fabricated PET/ITO/PEDOT:PSS/electrolyte/CNT/PET device exhibited reproducible and clear color switching from light to dark blue with a coloration efficiency of 88 cm2 C−1. This study highlights novel architecture of ECDs using CNT-based films as conductive counter electrode.

Compositions in the La2−xPrxNiO4+δ series offer an attractive balance of chemical stability and electrochemical performance for use as cathode materials in solid oxide fuel cells (SOFCs). A detailed crystallographic study of this system has been performed, combining both high resolution synchrotron and neutron powder diffraction data, in order to investigate structural details of the series as a function of composition, temperature and oxygen over-stoichiometry. The monoclinic structure (space group F2/m) of ambient temperature Pr-rich compositions for 1.0 < x ≤ 2.0 is discussed in terms of octahedra tilt arrangements and possible long-range structural modulations. In situ synchrotron diffraction experiments and TEM are employed to examine the role of temperature and interstitial oxygen on these structural distortions. With increasing La substitution, a region of mixed monoclinic and tetragonal phases is described for 0.5 ≤ x ≤ 1.0. La-Rich compositions are found to be single phase tetragonal (F4/mmm for 0 < x < 0.5) or orthorhombic (Fmmm for x = 0). Possible origins and electrochemical property consequences of the refined structural trends are considered.

International audience; NaMoO2 was synthesized as a layered oxide from the reaction between the layered oxide Na2/3MoO2 and metal sodium. Its structure was determined from high-resolution powder X-ray diffraction, and it can be described as an α-NaFeO2 distorted structure in which sodium ions and molybdenum atoms occupy octahedral interstitial sites. Chains of “diamond-like” clusters of molybdenum were evidenced in the [MoO2] layers resulting from the Peierls distortion expected in a two-dimensional triangular lattice formed by transition metal atoms with a d3 electronic configuration. Molybdenum–molybdenum distances as short as 2.58 Å were found in these clusters. The magnetic moment recorded at low temperatures and at room temperature showed that NaMoO2 presents a very low magnetic susceptibility compatible with the localization of the 4d electrons in the Mo–Mo bonds. This localization was confirmed by DFT calculation that showed the NaMoO2 was diamagnetic at 0 K. A sodium battery was built using NaMoO2 as the positive electrode material, and we found that sodium ions can be reversibly deintercalated and intercalated in NaMoO2, indicating that this compound is one of the many phases existing in the NaxMoO2 system.

NaMoO

International audience; The structure of a novel compound, LiFeV2O7, has been determined from single-crystal X-ray diffraction data. The phase crystallizes in the non-centrosymmetric monoclinic Cc space group. The structure can be described as a layered type compound alternating (Li,Fe)–O sheets and V–O chains that are perpendicular to the [101] direction. Within the (Li,Fe)–O sheets, “hexagonal” holes are formed and assembled into tunnels running parallel to the [201] direction and hosting the vanadium atoms. Original (V4O14)8– strings are observed within the structure in association with well-known (V2O7)4– pyrovanadate units. Both units alternate parallel to the [−101] direction. LiFeV2O7 displays a reversible insertion–deinsertion mechanism for Li+ ions. The theoretical capacity for the insertion of one Li+ into LiFeV2O7 reaches 97 mAh/g. When the compound is cycled between 3.50 and 2.35 V versus Li+/Li, the electrochemical curve displays an initial capacity of 100 mAh/g, with 85% of this capacity retained after 60 cycles. No evidence of the formation of Fe4+ upon oxidation to a high voltage was observed. LiFeV2O7 represents the first reported phase in the Li2O–Fe2O3–V2O5 ternary diagram with electrochemical activities.

International audience; Nano-CoF3 powders were synthesized by direct fluorination at various temperatures (up to 300 °C) of cobalt nanoparticles and their electrochemical features in lithium battery were investigated. The structure and composition of the raw and fluorinated materials are explored by SEM/TEM, HRTEM, XRD and XPS experiments. The influence of the fluorination temperature on the crystallite size has been evidenced by XRD. It is shown that such fluorination process allows the direct synthesis of nano-CoF3, at TF2 = 100 °C. The XPS investigation of mixtures of CoF3 and acetylene black has shown that, when handled in very dry atmospheres, CoF3-based samples can be used to prepare electrodes for Li-ion batteries in safe conditions. The electrochemical reaction of nano-CoF3 powders vs. lithium metal studied in organic medium involves a conversion process as described in the case of cobalt oxide. Successive impedance measurements were carried out at different discharge states to follow the modifications occurring at the electrode/electrolyte interface during the discharge step. The evolution of the reversible capacity retention of Li+ vs. time capacity of the powdered materials as well as the cycle life of the battery were investigated as a function of the fluorination temperature used for the preparation of the cobalt fluoride nanopowders. The best electrochemical performances were obtained with nano-CoF3 powders prepared at fluorination temperature of 100 °C, for which a reversible capacity of about 390 mAh/g is obtained after subsequent cycles.

Cet article est consacre aux arbitres de football en France, c’est-a-dire ceux qui regulent plus de 600000 rencontres sportives chaque annee. Il s’agit ici de relever les principales dimensions d’une activite complexe, de caracteriser l’heterogeneite d’un groupe et de questionner le mode de gouvernement auquel il contribue. Les elements sociologiques proposes proviennent d’une revue de litterature, d’une passation de questionnaires realisee aupres de 5000 arbitres francais, de 29 entretiens touchant presque tous les niveaux de l’arbitrage. L’article montre l’existence de profils d’arbitres varies et les inegales distributions et consistances de pouvoirs qui en decoulent. Ainsi l’usage du pouvoir et sa dimension discretionnaire sont-ils dependants de la position occupee par l’arbitre dans sa hierarchie et dans la carriere.

International audience; Using a synthesis route based on carbon as the reducing agent mixed with Nb-doped V2O5 nanopowders, highly crystallized Nb-doped VO2 (M) particles, with tunable content of niobium (Nb), are successfully prepared. The morphology and the crystalline structure are first studied in regard to synthesis parameters and chemical composition for various thermal treatment temperatures/durations and niobium doping concentrations. The second part of this paper is devoted to the control, in Nb-doped VO2, of the phase transition temperature from monoclinic to rutile (M → R transition) versus the niobium doping concentration associated with thermochromic properties and different property changes characterized by differential scanning calorimetry and magnetic and electrical measurements. The niobium introduction allows the decrease of the thermochromic transition from 68 °C down to around room temperature for an effective Nb concentration of approximatively 6 mol % for the V0.94Nb0.06O2±δ composition. A significant result is the decrease of both the hysteresis width as well as the phase transition amplitude supported by latent heat, magnetic behavior, and electrical transport versus niobium concentration. These phenomena are correlated to the breaking of the V–V pairing occurring in the monoclinic form when niobium ions are introduced. Finally, a deep interpretation of the Nb-doped VO2 magnetic behavior is performed considering the impact of niobium concentration and crystallite sizes on the intensity of the Curie magnetic residue plus Van Vleck susceptibility in the low temperature form (M) and on the intensity of the Pauli magnetism of the high temperature form (R).

International audience; To develop materials with enhanced electrochemical properties, an original synthesis strategy based on the exfoliation and restacking of manganese and cobalt layered transition metal oxides has been explored. Successful exfoliation yielded “building nanoblocks”, which were further reassembled in mixed nanocomposites, by modifications of electrostatic interactions in solution. Three methods were tested, differing by the acidification procedure and time of mixing. The restacking conditions play a key role on the microstructural homogeneity of the nanocomposites. Such a nanocomposite approach marrying a good electronic conductor (cobalt oxyhydroxide) with a pseudocapacitive material (manganese oxide) should thus be very beneficial for development of highly efficient pseudocapacitors.

International audience; Novel design of electrochromic devices (ECDs) known for their ability to modify optical properties under an applied voltage, based on a minimization of the number of layers is reported. The use of a metallic electrode, playing the role of both the conductive layer and the counter electrode, allows us to simplify the assembly of a commonly five-layer battery-type device to four-layer ECD. Further minimization of the number of layers is achieved using a conductive and electrochromic material. The novelty of the device configuration is illustrated using poly(3,4-ethylenedioxythiophene) (PEDOT)-based materials as EC layer, lithium-based ionic liquid as electrolyte, and Ag as counter electrode. Such a four- or three-layer ECD deposited on paper substrate switches from light to deep blue in a narrow 0.7 V voltage window. Preliminary investigations of the mechanism indicate traces of Ag on the PEDOT layer upon cycling. Finally, the printed ECD is successfully activated using a mobile phone.

International audience; The mechanism of the displacive phase transition in VO2 near the transition temperature is discussed in terms of a geometrical approach, combining simple calculations based on the Brown's band valence model and in situ X-ray diffraction experimental results. Considering that the structural origin is well linked to the electrostatic potential optimization as in a Peierls model, our geometrical calculations and experimental studies are in agreement and suggest that VO2 phase transition is the consequence of very short atomic shifts mainly associated to a decrease of the 2nd sphere coulombic interactions. Hence, at a given temperature, the allotropic form (monoclinic versus rutile form) offering the largest unit-cell volume is stabilized over the lower unit-cell volume allotropic, while the transition occurs at the intercept of the unit cell variation versus temperature of the two forms, which exhibit significantly different thermal expansion coefficients.

The mechanism of the displacive phase transition in VO2 near the transition temperature is discussed in terms of a geometrical approach, combining simple calculations based on the Brown's band valence model and in situ X-ray diffraction experimental results. Considering that the structural origin is well linked to the electrostatic potential optimization as in a Peierls model, our geometrical calculations and experimental studies are in agreement and suggest that VO2 phase transition is the consequence of very short atomic shifts mainly associated to a decrease of the 2nd sphere coulombic interactions. Hence, at a given temperature, the allotropic form (monoclinic versus rutile form) offering the largest unit-cell volume is stabilized over the lower unit-cell volume allotropic, while the transition occurs at the intercept of the unit cell variation versus temperature of the two forms, which exhibit significantly different thermal expansion coefficients.

This article focuses on the problem of violence occurring in male amateur team sports. On the basis of a series of surveys performed between 2002 and 2010, we propose to contrast indigenous explana...

International audience; A low-cost and facile method to synthesize highly crystallized VO2 (M1) particles is proposed, using carbon black as the reducing agent mixed with V2O5 nanopowders comparing two types of vacuum systems for the thermal activation. In a sealed vacuum system, CO gas is generated in the first reductive step, and continues to reduce the new born VO2, until all the V (+4) is reduced to V (+3), resulting in V2O3 formation at 1000 °C. In contrast, in a dynamic vacuum system, CO gas is ejected through pumping as soon as it is generated, leading to the formation of pure VO2 (M1) at high temperatures (i.e. in the range 700 °C ≤ T ≤ 1000 °C). The evolution of the carbon content, determined by CHNS, of each sample versus the synthesis conditions, namely temperature and type of vacuum system, confirms that the transformation of V (+5) into V (+4) or V (+3) can be controlled. The characterization of the morphologies and crystal structures of two synthesized VO2 (M1) at 700 °C and 1000 °C shows the possibility to tune the crystallite size from 1.8 to more than 5 μm, with a uniform size distribution and highly crystallized powders. High purity VO2 (M1) leads to strong physical properties illustrated by a high latent energy (∼55 J g−1) during the phase transition obtained from DSC as well as high resistivity changes. In addition, with this method, dopants such as Ti4+ or Al3+ can be successfully introduced into VO2 (M1) thanks to the preparation of Al or Ti-doped nano-V2O5 by co-precipitation in polyol medium before carbon-reduction.

A low-cost and facile method to synthesize highly crystallized VO2 (M1) particles is proposed, using carbon black as the reducing agent mixed with V2O5 nanopowders comparing two types of vacuum systems for the thermal activation. In a sealed vacuum system, CO gas is generated in the first reductive step, and continues to reduce the new born VO2, until all the V (+4) is reduced to V (+3), resulting in V2O3 formation at 1000 °C. In contrast, in a dynamic vacuum system, CO gas is ejected through pumping as soon as it is generated, leading to the formation of pure VO2 (M1) at high temperatures (i.e. in the range 700 °C ≤ T ≤ 1000 °C). The evolution of the carbon content, determined by CHNS, of each sample versus the synthesis conditions, namely temperature and type of vacuum system, confirms that the transformation of V (+5) into V (+4) or V (+3) can be controlled. The characterization of the morphologies and crystal structures of two synthesized VO2 (M1) at 700 °C and 1000 °C shows the possibility to tune the crystallite size from 1.8 to more than 5 μm, with a uniform size distribution and highly crystallized powders. High purity VO2 (M1) leads to strong physical properties illustrated by a high latent energy (∼55 J g-1) during the phase transition obtained from DSC as well as high resistivity changes. In addition, with this method, dopants such as Ti4+ or Al3+ can be successfully introduced into VO2 (M1) thanks to the preparation of Al or Ti-doped nano-V2O5 by co-precipitation in polyol medium before carbon-reduction.

Le basculement du free fight au mixed martial arts (MMA) se traduit par la mise en place d’un cadrage reglementaire amorcant, dans les annees 2000, son institutionnalisation. En France, il n’existe pas de federation dediee organisant la pratique alors que se developpe une pratique amateur sans que celle-ci ne soit jamais finement etudiee. Comment se structurent et s’organisent les pratiques dans ces clubs ? Qui sont les pratiquants et qu’y font-ils exactement ? Pour apporter des elements de reponse, cet article s’appuie sur une enquete empruntant a la demarche ethnographique menee aupres de deux clubs affilies a l’etranger au MMA. Cette contribution ne doit pas seulement a la specificite de son terrain. Elle tient surtout a la mise en perspective des donnees ethnographiques evaluees a l’aune d’une discussion de la sportivisation, de-sportivisation. Entre conformisme au modele sportif classique et revendication d’exceptionnalite, entre un sport bâti sur la mise en scene de l’affrontement « violent » dans lequel le combat occupe une place reduite a la portion congrue, entre une discipline dont les origines pronaient l’absence de regles devenue sur nos terrains une pratique rigoureusement controlee, le MMA ici observe semble relever d’une pratique physique dite « sportivisee ».

Compositions in the La2-xPrxNiO4+δ series offer an attractive balance of chemical stability and electrochemical performance for use as cathode materials in solid oxide fuel cells (SOFCs). A detailed crystallographic study of this system has been performed, combining both high resolution synchrotron and neutron powder diffraction data, in order to investigate structural details of the series as a function of composition, temperature and oxygen over-stoichiometry. The monoclinic structure (space group F2/m) of ambient temperature Pr-rich compositions for 1.0x ≤ 2.0 is discussed in terms of octahedra tilt arrangements and possible long-range structural modulations. In situ synchrotron diffraction experiments and TEM are employed to examine the role of temperature and interstitial oxygen on these structural distortions. With increasing La substitution, a region of mixed monoclinic and tetragonal phases is described for 0.5 ≤ x ≤ 1.0. La-Rich compositions are found to be single phase tetragonal (F4/mmm for 0x0.5) or orthorhombic (Fmmm for x = 0). Possible origins and electrochemical property consequences of the refined structural trends are considered.

International audience; CaSn(OH)6, CaSnO3 and CaSnF6 compounds were elaborated from a “one-batch” synthesis route: the coprecipitation of the pure double hydroxide leads to pure double oxide or fluoride after annealing treatments under air or HF as anhydrous gas, respectively. Structural and morphological features of the three matrices were carefully investigated by X Ray Diffraction analysis and Scanning Electron Microscopy, respectively. In addition, the luminescent properties of the Pr-doped compounds were performed and compared. The nanometric size of the double hydroxide inhibits the luminescence. The interpretation of the emission spectra obtained for Pr-doped CaSnO3 and CaSnF6 compounds is based on the covalence/ionic balance of the M–O or M–F bonds.

Highly crystallized monoclinic vanadium dioxide, VO

International audience; Vanadium dioxide is the key thermochromic compound for the next generation of smart windows. Monoclinic vanadium dioxide with tuned crystallinity is synthesized by a two-step thermal treatment: thermolysis of vanadyl ethylene glycolate and postannealing of the poorly crystallized VO2 powder. The proportion of crystallized VO2, calculated with the Fullprof program, increases from 44% to 79% and 100% with increasing annealing temperature up to 700 °C. Besides, V2O3 and V2O5 with particular microstructures are also successfully prepared using this method.

International audience; The praseodymium nickelate PrNiO3-δ was recently identified as one of the decomposition products of Pr2NiO4+δ oxygen electrode, raising the question of the role of this perovskite compound on the Pr2NiO4+δ performance and ageing behaviour. Herein, the electrochemical properties of PrNiO3-δ as cathode for Solid Oxide Fuel Cells (SOFCs) is reported. PrNiO3-δ, synthesized from the citrate-nitrate route, cristallizes in an orthorhombic structure (S.G.: Pnma). Under air, a transition to high temperature rhombohedral structure (S.G.: R-3c) occurs at around 600 °C, while its oxygen vacancy amount increases from δ 0.05 at room temperature up to 0.10 at high temperature. Thermal gravimetry analysis (TGA) measurements coupled with X-ray diffraction (XRD) characterizations show that above 1000 °C, in air, PrNiO3-δ starts to decompose into Pr2NiO4+δ and NiO through an intermediate transformation into Pr4Ni3O10+δ. The value of the polarization resistance (Rp) of co-sintered GDC-PrNiO3-δ electrode, at 950 °C in air for 2 h, is 0.91 Ω cm2 at 600 °C under air. It remains much higher than that of co-sintered GDC-Pr2NiO4+δ electrode (Rp = 0.15 Ω cm2), which means that the perovskite does not play any significant role in the electrochemical performance during long term operation of the Pr2NiO4+δ electrode

International audience; The synthesis of a Co-doped or Fe-doped La(Ga,Al)O3 perovskite via the Pechini process aimed to achieve a color change induced by temperature and associated with spin crossover (SCO). In Fe-doped samples, iron was shown to be in the high-spin state, whereas SCO from the low-spin to the high-spin configuration was detected in Co-doped compounds when the temperature increased. Fe-doped compounds clearly adopted the high-spin configuration even down to 4 K on the basis of Mössbauer spectroscopic analysis. The original SCO phenomenon in the Co-doped compounds LaGa1-xCoxO3 (0 < x < 0.1) was evidenced and discussed on the basis of in situ X-ray diffraction analysis and UV-vis spectroscopy. This SCO is progressive as a function of temperature and occurs over a broad range of temperatures between roughly 300 °C and 600 °C. The determination of a crystal field strength of about 2 eV and a Racah parameter B of about 500 cm-1 for Co3+ (3d6) ions show that these values allow the occurrence of SCO. Hence, this study shows the possibility of using LaGa1-xCoxO3 compounds as thermal sensors at low Co contents (x = 0.02). The competition between steric and electronic effects in LaGaO3 in which Co3+ is stabilized in the LS state shows that electronic effects with the creation of M-O covalent bonds are predominant and contribute to the stabilization of a high crystal field around Co3+ (LS) although its ionic radius is smaller in comparison with that of Ga3+.

International audience; AMoO4 compounds (A = Co, Mn, Fe, Ni, Cu, or Zn) exhibit a first-order phase transition associated with piezochromic and thermochromic phenomena, as demonstrated in previous studies. In this study, neutron diffraction patterns were collected for CuMo0.9W0.1O4 samples across the hysteresis cycle to accurately characterize the structural evolution (i.e., cell parameters and atomic positions) versus temperature. This study provides information regarding the phase-transition origin. In accordance with the Birch–Murnaghan model, the phase transition is due to the higher compressibility coefficient, despite the presence of the shorter bonds for the high-temperature form. The cell-volume difference of 13% between the high and low temperature forms leads to additional exotic properties: the thermosalient effect (“jumping crystals”) associated with a certain crystallite fracture (along the −101 plane) is shown.

The synthesis of a Co-doped or Fe-doped La(Ga,Al)O

International audience; Monoclinic and cubic europium-doped Gd2O3 structures were selectively synthesized by the glycine–nitrate process by fine control of the synthesis temperature through the crucial fuel/oxidant ratio. The cubic phase is obtained under fuel-rich conditions, whereas stoichiometric conditions induce the simultaneous formation of cubic and monoclinic polymorphs. The samples were subjected to appropriate sintering to obtain highly crystalline and carbon-free materials. The average nanoparticle (NP) size determined by TEM for these nanopowders (23 nm) agrees with the average crystallite sizes obtained from XRD Rietveld analysis; therefore, the particles are monocrystalline. Both electron energy loss spectroscopy (EELS) and photoluminescence studies showed that the europium-doped NPs are highly luminescent, and the Eu3+ ions are homogeneously distributed over the whole material as well as over the two gadolinium crystallographic sites of the cubic phase. These fluorescent NPs exhibit relaxivities that define them as potential T1 contrast agents for further biomedical applications.

International audience; Spin-crossover (SCO) triazole-based coordination polymers can be synthesized by micelle techniques, which almost always lead to rod-shaped nanoparticles. In order to notably reach new morphologies, we explore here the potentiality of the spray-drying (SD) method to get SCO materials. Three SCO coordination polymers and a mononuclear complex are investigated. In all cases, the SD method obtains particles definitely showing SCO. The features of the latter are yet always different from those of the referenced materials, in the sense that SCO is more gradual and incomplete, in adequacy with the poor crystallinity of the powders obtained by SD. In the case of coordination polymers, the particles are preferentially spherical. Indications of possible polymorphism and/or new materials induced by the use of the SD method are evidenced. In the case of the mononuclear complex, the SD method has allowed reproducing, in a quick and easy way, the well-known bulk compound. This exploratory work demonstrates the relevance of the concept and opens the way to a systematic scrutiny of all the experimental parameters to tune the size, morphology, and properties of the SD-synthesized SCO particles.

Ce livre, ouvert par une preface de Jacques Birouste, est tres largement inspire du memoire d’habilitation a diriger des recherches de Sylvain Ferez. L’auteur y presente la synthese articulee « d’une decennie de recherche » initiee en DEA, poursuivie en doctorat puis dans l’exercice du metier d’enseignant-chercheur. Les travaux exposes ont en commun d’etudier des « crises de corporeite » (definies par l’auteur comme des ruptures ou des decalages par rapport a certaines normes corporelles « do...

In an attempt to observe hydrogen (deuterium) induced atomic ordering of transition (T) metals in AB 5 -type derivative structures neutron diffraction and hydrogen cycling experiments were performed on a nickel substituted boride sample of composition NdCo 3 NiB. While uncycled NdCo 3 NiB crystallizes with the centrosymmetric CeCo 4 B-type structure (space group P 6/ mmm ), hydrogenation (deuteration) and cycling of NdCo 3 NiB at 373 K between 0 and 60 bar hydrogen (deuterium) atmosphere induces a symmetry decrease to non-centrosymmetric space group P 6 mm . Evidence for partial cobalt/nickel ordering is found in pristine NdCo 3 NiB but not in its deuteride NdCo 3 NiBD x . Compared to boron free AB 5 -type compounds deuterium occupies only those interstices that have no boron atom in their coordination sphere. These findings are consistent with repulsive B–D interactions. At 303 K the hydrogen equilibrium plateau pressure of the NdCo 3 NiB–H system is about 2 bar, and the hydrogen content at 10 bar is about 3.1 H atoms per formula unit.

In order to discover innovative electrode and electrolyte battery materials responding to specific needs in terms of capacity, working voltage, polarisation, alkali insertion mechanisms, it appears interesting to explore various insertion chemistries. With this in mind, our study was dedicated on the structural properties and electrochemical performances of iron vanadates positive electrode for Li batteries. More specifically, our groups focussed on the search for new stable phases in the Li2O - Fe2O3 - V2O5 ternary system with respect to several vanadates (FeVO4, NaCuFe2(VO4)3, β-Cu3Fe4(VO4)6, …), which structural and electrochemical properties upon Li insertion have been highlighted in previous work [1]. Among the Li2O - Fe2O3 - V2O5 system, this presentation is dedicated to two new compounds, which were not known from the literature. Both materials were obtained through solid synthesis routes, after optimising the annealing parameters to reach pure phases. After determination of the structure using single crystal X-Ray Diffraction, their physical and electrochemical properties were thoroughly characterized using SEM, Mossbauer spectroscopy, galvanostatic and potentiostatic cycling. Electrochemical characterizations in half cells resulted in finding the optimal voltage window to enhance the capacity retention of the material as compared to previously studied vanadates. The galvanostatic curves indicated complex mechanisms for both materials involving several monophasic and biphasic steps upon Li insertion (see figure for the structure of LiFeV2O7 viewed along the [-101] direction and its electrochemical curve in half cell). Mossbauer spectroscopy allows assessing the oxidation state of iron atoms in the structures before and upon the electrochemical processes. [1] Patoux, S., Richardson, T.J. “Lithium insertion chemistry of some iron vanadates”, Electrochemistry Communications, 9 (3), pp. 485-491 (2007). [2] Benabed, Y., Castro, L., Penin, N., Darriet, J., Dollé, M. “Synthesis, Structure, and Electrochemical Properties of LiFeV2O7”, Chemistry of Materials, 29 (21), pp. 9292-9299 (2017). Figure 1

A combination of in situ synchrotron powder diffraction energy minimization (DFT) and Raman and infrared spectroscopy confirmed porous interpenetrated 3D framework structures of recently discovered alkali metalminus;zinc borohydrides AZn2(BH4)5 (A = Li Na). In the less zinc rich NaZn(BH4)3 the 3D framework structural model has been confirmed but with a slightly modified description giving an isolated triangular anion [Zn(BH4)3]minus; rather than a 1D anionic chain {[Zn(BH4)3]n}nminus;. Another polymorph of NaZn(BH4)3 isostructural to a new compound LiZn(BH4)3 is proposed by energy minimization. Both compounds the new NaZn(BH4)3 polymorph and LiZn(BH4)3 are however not observed experimentally at ambient pressure and in the temperature range of 100minus;400 K. The alkali metalminus;zinc borohydride NaZn(BH4)3 containing the triangular anion [Zn(BH4)3]minus; is an equivalent of recently characterized alkali metalminus;scandium borohydrides NaSc(BH4)4 and LiSc(BH4)4 based on the tetrahedral [Sc(BH4)4]minus; complex anion.

L’article concerne les agressions dans le sport amateur. Plus precisement celles qui impliquent le joueur, l’encadrant, l’arbitre, le public. Sur la base d’une etude comparee de trois activites (le football, le basket-ball et le handball), il s’agit de quantifier les phenomenes et de proposer des elements d’explication. Fondes sur des enquetes de terrain accomplies dans le departement du Pasde-Calais, ils derivent de la prise en compte d’un rapport differencie au respect des normes. Compose de 16 clubs, l’echantillon presente par consequent quelques-uns des attributs indispensables pour arreter une sociologie comparative. Elle met moins en evidence l’influence des caracteristiques ludomotrices liees au type de pratique que celle relevant de facteurs organisationnels : tous semblent dependre fortement de la masse des licencies.

International audience; The microwave-assisted route allows the synthesis of a new Ti hydroxyfluoride adopting a derived form of a ReO3-type network. Combined techniques such as (i) powder X-ray and neutron diffraction coupled with electron microscopy; (ii) chemical analysis and density measurements; and (iii) FTIR and TGA analyses support the occurrence of Ti vacancies and the stabilization of hydroxyl groups in the vicinity of Ti4+ cations. A superstructure of the ReO3 network has been proposed with two Ti sites and two anionic (OH/F) positions. This original compound exhibits UV-shielding properties with an optical band gap around 3.2 eV and could be considered for potential applications as protective UV absorbers.The O(2p)−Ti(3d) charge transfer band, responsible for this absorption, implies the OH groups and the nonbonding character of the 2p valence band. By changing the synthesis conditions which become reducing, Ti3+ can be stabilized in this network in an elongated octahedral site as revealed by ESR experiments and UV−visible spectroscopy. This is a second example following the recently prepared Al-based fluoride hydrate with Al vacancies, in which a polarizing cation such as Ti4+ can accommodate cationic vacancies.

The need for a safe, reliable and cheap method for hydrogen transportation has prompted an intense effort in the synthesis of novel hydrides. To direct the search for better materials, it is essential to understand the bonding present in these systems. A newly synthesized material is LaMg2PdH7 which is best formulated as {La3+}{Mg2+}2{[PdH4]4−}{H−}3. Thus hydrogen is formally present both as a free hydride ion and also as a covalently bound ligand. The combination of inelastic neutron scattering (INS), infrared and Raman spectroscopies and periodic density functional theory (DFT) has been used to characterise the material. We find that the material is less ionic than Ba2[PdH4], which also contains [PdH4]4−. The charges carried by both the coordinating and free hydrides are similar which hints at a degree of covalency in the interactions between the interstitial hydrides and the lanthanum and magnesium ions.

International audience; Because of a very low thermodynamic stability, obtaining a pure monophasic compound of ferric pseudobrookite is quite difficult to achieve. Indeed, the low reticular energy of this phase leads easily to its decomposition and the occurrence of the secondary phases: hematite (Fe2O3) and/or rutile (TiO2). Samples with global composition Fe2-xTi1+xO5 (x = 0, 0.05, and 0.10) have been synthesized by the Pechini route and, thereafter, thermally treated at different temperatures. The concentrations of Fe2O3 and TiO2 secondary phases were accurately determined and correlated with the target compositions and the synthesis parameters, especially the thermal treatment temperature. As revealed by Mössbauer spectroscopy, all iron ions are at the III+ oxidation state. Thus, the formation of hematite or rutile as a secondary phase may be related to the occurrence of cationic vacancies within the pseudobrookite structure, with the amount of vacancies depending on the annealing temperature. In light of the presented results, it appears unreasonable to propose a "fixed" binary phase diagram for such a complex system. Furthermore, the occurrence of cationic vacancies induces a coloration change (darkening), preventing any industrial use of this reddish-brown pseudobrookite as a ceramic pigment.

International audience; The present work is focused on the study of Pr4Ni3O10+δ as a new cathode material for Solid Oxide Fuel Cells (SOFCs). The structural study leads to an indexation in orthorhombic structure with Fmmm space group, this structure being thermally stable throughout the temperature range up to 1000 °C under air and oxygen. The variation of oxygen content (10+δ) as a function of temperature under different atmospheres show that Pr4Ni3O10+δ is always oxygen over-stoichiometric, which further suggests its MIEC properties. The polarization resistance (Rp) of Pr4Ni3O10+δ electrode is measured for GDC/co-sintered and two-step sintered half cells. The Rp for co-sintered sample is found to be 0.16 Ω cm2 at 600 °C under air, which is as low as the one of highest performing Pr2NiO4+δ nickelate (Rp = 0.15 Ω cm2 at 600 °C). Moreover, an anode supported (Ni-YSZ//YSZ) single cell including GDC//Pr4Ni3O10+δ co-sintered electrode shows a maximum power density of 1.60 W cm−2 at 800 °C and 0.68 W cm−2 at 700 °C. Here, the work is emphasized on the very close electrochemical performance of Pr4Ni3O10+δ compared to the one of Pr2NiO4+δ with higher chemical stability, which gives great interests to consider this material as a very interesting oxygen-electrode for SOFCs.

Hydrogenation of the intermetallic compound LaMg 2 Pd at 200 °C and 10 bar leads to a complex metal hydride of composition LaMg 2 PdH 7 . Its structure has orthorhombic symmetry and displays tetrahedral [PdH 4 ] 4- anions. The Pd-H bond distances as measured on the deuteride range from 1.71 to 1.78 A and the H-Pd-H bond angles from 95° to 122°. Three additional hydride anions H - occupy La 2 Mg 2 -type interstices having tetrahedral metal configurations. Band structure calculations suggest the hydride to be non-metallic and to have a band gap of ∼1.0eV. The compound desorbs hydrogen at 125 °C yielding a pressure of more than 1 bar absolute.

BaBiBO4, or BaBi(BO3)O, is a novel borate oxide which has been synthesized by solid-state reaction at temperatures below 650 °C and 1 atm pressure. Its crystal structure has been determined from powder X-ray diffraction data and refined from powder neutron diffraction data (non-centrosymmetric Pna21 space group, a = 8.5817 ( 7 ) , b = 9.6802 ( 7 ) , c = 5.1505 ( 4 ) A , Z = 4 ). The structure is built of [001] chains of edge-sharing BO3 and BiO5 groups interleaved with Ba2+ cations. The measurement of the nonlinear optical properties of a powder sample by the Kurtz–Perry method yielded an efficiency for second-harmonic generation equal to five times that of KH2PO4.

The bismuth borates Bi2ZnB2O7 and CaBiGaB2O7 have been synthesized by solid-state reactions at temperatures in the 650−825 °C range at 1 atm pressure. These compounds are the only synthetic diborate members of the melilite family, A2XZ2O7, in which layers of A cations alternate with XZ2O7 tetrahedral layers. Except for CdBiGaB2O7, the synthesis of other substituted bismuth borate melilites has been unsuccessful. The crystal structures of Bi2ZnB2O7 and CaBiGaB2O7 have been determined by powder X-ray diffraction and refined by the Rietveld method using powder neutron diffraction data. CaBiGaB2O7 adopts the regular tetragonal melilite structure (P421m space group, Z = 2) containing B2O7 tetrahedral dimers. The refinement of split eight-coordinated sites for the Ca2+ and Bi3+ interlayer cations suggests the presence of additional disorder. Bi2ZnB2O7 adopts a unique orthorhombic melilite superstructure (Pba2 space group, Z = 4) containing both tetrahedral B2O7 and triangular B2O5 dimers. The Bi3+ cations occu...

Na{sub 6}B{sub 13}O{sub 22.5} (B/Na=2.17) single crystals were obtained by heating, melting and appropriately cooling borax, Na{sub 2}[B{sub 4}O{sub 5}(OH){sub 4}].8H{sub 2}O. Its formula has been determined by the resolution of the structure from single-crystal X-ray diffraction data. The compound crystallizes in the noncentrosymmetric orthorhombic Iba2 space group, with the following unit cell parameters: a=33.359(11)A, b=9.554(3)A, c=10.644(4)A; V=3392.4(19)A{sup 3}; Z=8. The crystal structure was solved from 3226 reflections until R{sub 1}=0.0385. It exhibits a three-dimensional framework built up from BO{sub 3} triangles ({delta}) and BO{sub 4} tetrahedra (T). Two kinds of borate groups can be considered forming two different double B{sub 3}O{sub 3} rings: two B{sub 4}O{sub 9} (linkage by two boron atoms) and one B{sub 5}O{sub 11} (linkage by one boron atom); the shorthand notation of the new fundamental building block (FBB) existing in this compound is: 13: {infinity}{sup 3} [(5: 3{delta}+2T)+2(4: 2{delta}+2T)]. The discovery of this new borate questions the real number of Na{sub 2}B{sub 4}O{sub 7} varieties. The existence of Na{sub 6}B{sub 13}O{sub 22.5} (B/Na=2.17) and of another recently discovered borate, Na{sub 3}B{sub 7}O{sub 12} (B/Na=2.33; FBB 7: {infinity}{sup 3} [(3: 2{delta}+T)+(3: {delta}+2T)+(1: {delta})], with a composition close to the long-known borate {alpha}-Na{sub 2}B{sub 4}O{sub 7} (B/Na=2;more » FBB 8: {infinity}{sup 3} [(5: 3{delta}+2T)+(3: 2{delta}+T)], may explain the very complex equilibria reported in the Na{sub 2}O-B{sub 2}O{sub 3} phase diagram, especially in this range of composition.« less

The crystal structure of Na 3 B 7 O 12 and Na 2 Tl 2 B 10 O 17 was determined by the single crystal X-ray diffraction method. The first one crystallizes in the triclinic system, space group P -1, with the following unit cell parameters: a =6.638(2) A, b =8.249(3) A, c =8.836(3) A, α =95.875(5)°, β =100.680(4)°, γ =99.688(4)°; V =464.2(2) A 3 ; Z =2. The crystal structure was solved from 1982 reflections until R 1 =0.0293. It exhibits a three-dimensional framework built up from BO 3 triangles (▵) and BO 4 tetrahedra (T). Three kinds of borate groups can be considered: B 3 O 7 and B 3 O 8 rings and BO 3 triangle; the shorthand notation of the fundamental building block (FBB) existing in this compound is: 7: ∞ 3 [(3: 2▵+T)+(3: ▵+2T)+(1: ▵)]. The second borate Na 2 Tl 2 B 10 O 17 crystallizes in the monoclinic system, space group C 2/ c , with a =21.711(10) A, b =6.446(3) A, c =10.952(5) A, β =105.897(8)°; V =1474.0(1) A 3 ; Z =4. The crystal structure was solved from 1884 reflections until R 1 =0.0387. It consists of a two-dimensional network of sharing corners BO 3 triangles and BO 4 tetrahedra forming B 5 O 11 double rings, leading to the FBB: 10: ∞ 2 2[(5: 3▵+2T)]. These two new borates were compared with the compounds M 3 B 7 O 12 (M=Li, Rb, Cs; B/M=2.33) and AgSrB 7 O 12 , and Cs 2 Na 2 B 10 O 17 and Cs 2 K 2 B 10 O 17 (M 2 M′ 2 B 10 O 17 , M and M′ monovalent elements; B/(M+M′)=2.5). The latter are isotype and isostructural of Na 2 Tl 2 B 10 O 17 . Na 3 B 7 O 12 is isotype and isostructural of Li 3 B 7 O 12 ; the three-dimensional structure of these two heptaborates is different from the two-dimensional structures of AgSrB 7 O 12 , Rb 3 B 7 O 12 and Cs 3 B 7 O 12 , which contain different FBBs with 7, 14 and 63 boron atoms, respectively.

The structure of α-CsB9O14 was re-examined because the first determination corresponded to a poor reliability factor (12.9%). Single crystals were obtained by heating, melting and slow cooling a stoichiometric mixture (1:4) of β-Cs[B5O6(OH)4]·2H2O and H3BO3. This compound crystallizes in the non-centrosymmetric orthorhombic space group P2221 (and not P4122) with the following parameters: a=8.732(2) A, b=8.767(3) A, c=15.736(4) A, V=1204.6(6) A3, Z=4; after taking into consideration twinning, the structure was refined from 3188 reflections until R1=0.0304. It consists of two infinite, interleaved three-dimensional boron-oxygen frameworks of the Fundamental Building Blocks formed by two B3O6 and one B3O7 groups; its shorthand notation is 9:∞3[(3:2Δ+T)+2(3:3Δ)] (Δ, triangle BO3 and T, tetrahedron BO4). Knowledge of the correct space group and the structure of α-CsB9O14 may help in the study of its physical properties, especially the non-linear optical ones.