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Designing solid electrolytes for all-solid-state-batteries that can withstand the extreme electrochemical conditions in contact with an alkali metal anode and a high-voltage cathode is challenging, especially when the battery is cycled beyond 4 V. Here we demonstrate that a hydroborate solid electrolyte Na-4(CB11H12)(2)(B12H12), built from two types of cage-like anions with different oxidative stability, can effectively passivate the interface to a 4 V-class cathode and prevent impedance growth during cycling. We show that [B12H12](2-) anions decompose below 4.2 V vs. Na+/Na to form a passivating interphase layer, while [CB11H12](-) anions remain intact, providing sufficient ionic conductivity across the layer. Our interface engineering strategy enables the first demonstration of a 4 V-class hydroborate-based all-solid-state battery combining a sodium metal anode and a cobalt-free Na-3(VOPO4)(2)F cathode without any artificial protective coating. When cycled to 4.15 V vs. Na+/Na, the cells feature a discharge capacity of 104 mA h g(-1) at C/10 and 99 mA h g(-1) at C/5, and an excellent capacity and energy retention of 78% and 76%, respectively, after 800 cycles at C/5 at

Metal hydroborates from M(BH4)n to Mx(B12H12)y currently attract a strong interest for potential applications in the field of hydrogen storage and more recently as solid ionic conductors. While thermodynamic data for the alkali borohydrides (MBH4) are well known, experimental data for other compounds are cruelly lacking. Using a combination of theoretical (DFT) and experimental data, we calculate the lattice enthalpy for a series of borohydrides. The comparison with literature data show that these lattice enthalpies are very similar to those of the corresponding metal bromides. This similarity is at the origin of a good correlation between the formation enthalpy of bromides and borohydrides which is then used to estimate the previously unknown formation enthalpy of MII(BH4)2 (MII= divalent cation) and Ln(BH4)3 (Ln=lanthanide). The Gibbs free energy of formation of M2(B12H12) (M=alkali metal) is also estimated.

We report the thermodynamic stabilities and the intrinsic strengths of three‐center‐two‐electron B−B−B and B−Hb−B bonds (urn:x-wiley:14394235:media:cphc201900364:cphc201900364-math-0001 : bridging hydrogen), and two‐center‐two‐electron B−Ht bonds (urn:x-wiley:14394235:media:cphc201900364:cphc201900364-math-0002 : terminal hydrogen) which can be served as a new, effective tool to determine the decisive role of the intermediates of hydrogenation/dehydrogenation reactions of borohydride. The calculated heats of formation were obtained with the G4 composite method and the intrinsic strengths of B−B−B, B−Hb−B, and B−Ht bonds were derived from local stretching force constants obtained at the B3LYP‐D2/cc‐pVTZ level of theory for 21 boron‐hydrogen compounds, including 19 intermediates. The Quantum Theory of Atoms in Molecules (QTAIM) was used to deepen the inside into the nature of B−B−B, B−Hb−B, and B−Ht bonds. We found that all of the experimentally identified intermediates hindering the reversibility of the decomposition reactions are thermodynamically stable and possess strong B−B−B, B−Hb−B, and B−Ht bonds. This proves that thermodynamic data and intrinsic B−B−B, B−Hb−B, and B−Ht bond strengths form a new, effective tool to characterize new (potential) intermediates and to predict their role for the reversibility of the hydrogenation/dehydrogenation reactions.

International audience; We have studied in detail the emission spectra of the white phosphor Ba7F12Cl2:Eu2+ as a function of Europium content, excitation wavelength and temperature. The change of the emission spectrum with excitation wavelength shows a systematic shift in the CIE chromaticity diagram from warm white upon excitation in the near UV (370 nm) to cold white upon excitation at shorter wavelengths. The observed intensity changes with europium concentration confirm that energy transfer takes place, which is both concentration and temperature dependent. Temperature and sample dependent lifetime studies show that the observed lifetimes do not change within experimental error between dilute and concentrated Eu-doped samples, and they remain constant between 5 K and room temperature. The second observation confirms the previous results that the thermal quenching of the white emission occurs at high temperature (200 °C). The combination of all observations suggests that the energy transfer takes place first between the normal 4f65 d1 states of the Eu ions located on the 3 different crystallographic sites of Ba, and is followed by subsequent relaxation to anomalous emission states whose emission lifetimes remain constant with sample concentration and temperature from 5 K to 300 K.

International audience; Ionothermal synthesis is a strongly growing research area due to the outstanding physical and chemical properties of ionic liquids (ILs) in the design of new materials, however, the interaction of these IL molecules with optical materials and their effect on the luminescence properties of the materials are poorly known. In this work, it is shown that the imidazolium based BmimBF4 ionic liquid, used as a solvent during the synthesis, tethers at the surface of the nanoparticles and influences the photoluminescence of the nanophosphor BaFBr:Eu2+ materials. In time resolved spectra, two different emissions are observed for the material synthesized by the ionothermal approach, one corresponding to Eu(II) 5d–4f transitions in the BaFBr host with a decay time of 843 ns and the other with a much faster decay time compared to the ionic liquid BmimBF4.

Cr-substituted and pristine Ba2In2O5·(H2O)x powders were synthesized by solid state reaction. The influence of Cr-substitution on the crystal structure, chemical composition, magnetic and optical properties were investigated. Powder X-ray diffraction (XRD), elemental analysis and TGA-MS reveal that with substitution of In for Cr, the unit cell volume and the unit cell parameter b increase together with the oxygen and hydrogen content. Magnetic property measurements indicate that Ba2In2O5·(H2O)x is diamagnetic in the temperature range of 2 K < T < 300 K becoming ferromagnetic upon Cr-substitution. In the UV–vis spectra of the Cr-substituted sample a distinctive shift of the absorption-edge energy from 430 to 690 nm was observed corresponding to a bandgap narrowing from 2.88 to 1.80 eV. The replacement of tetrahedral InO4 units by octahedral CrO6 units was found to be the main factor for the drastic change of the magnetic and optical properties.

Rare-earth borohydrides have recently attracted a strong interest as potential hydrogen storage materials. While the local structure of the BH4 − ion can be probed using vibrational spectroscopy, the local structure of the rare-earth ion can be studied using luminescence spectroscopy. This is reported here for Tb(BH4)3 and its solvate with S(CH3)2. The spectra clearly show smaller CF splittings for the unsolvated compound. These experimental data are compared with recent DFT+U calculations of the energy levels and CF splittings for Tb(BH4)3 and show that these calculations significantly overestimate the experimental results.

Metal borohydrides have been studied since the beginning of this century as potential hydrogen storage materials due to their high gravimetric hydrogen content. Many new compounds have been synthesized and characterized, however to date the main problem are the kinetics of dehydrogenation and rehydrogenation. In this review we address thermodynamical and chemical properties of boron hydrogen compounds which come into play for hydrogen storage and which must be considered in the search for efficient catalysts. More recently, closo and nido hydridoborate and related closo hydridocarborate compounds have been identified as good ionic conductors for all-solid-state lithium or sodium batteries. The properties of these fascinating and very promising compounds for battery applications are illustrated with recent literature results.

International audience; We report on the identification and survey of the Pb 4 Ln 2 O 7 series (Ln = La, Gd, Sm and Nd) which turn out to be real van der Waals 2D oxides. In the neutral layers, strong covalent Pb-O bonds together with external stereoactive Pb 2+ lone pairs, which act as sensitizers, lead to an ideal matrix for enhanced and tunable luminescence by lanthanide emitters, tested here for Sm 3+ and Eu 3+ doping. DFT calculations and preliminary ex-solution experiments validate the weak bonding between the layers separated by 3.5 Å and suggest a indirect to direct crossover realized by isolating the layers.

We report on a particularly stable 3 V all-solid-state sodium–ion battery built using a closo-borate based electrolyte, namely Na2(B12H12)0.5(B10H10)0.5. Battery performance is enhanced through the creation of an intimate cathode–electrolyte interface resulting in reversible and stable cycling with a capacity of 85 mA h g−1 at C/20 and 80 mA h g−1 at C/5 with more than 90% capacity retention after 20 cycles at C/20 and 85% after 250 cycles at C/5. We also discuss the effect of cycling outside the electrochemical stability window and show that electrolyte decomposition leads to faster though not critical capacity fading. Our results demonstrate that owing to their high stability and conductivity closo-borate based electrolytes could play a significant role in the development of a competitive all-solid-state sodium–ion battery technology.

The characterization of boron-hydrogen compounds is an active research area which encompasses subjects as diverse as the chemistry and structures of closoboranes or the thermal decomposition mechanism of the borohydrides. Due to their high gravimetric hydrogen content, borohydrides are considered as potential hydrogen storage materials. Their thermal decompositions are multistep processes, for which the intermediate products are not easily identified. To help address this issue, we have extensively investigated the vibrational and NMR properties of 21 relevant B m H n z − boron-hydrogen species ( m = 1–12; n = 1–14; z = 0–2) within density functional theory. We could thus show that the B3LYP-D2 dispersion-corrected hybrid can be used in combination with the large cc-pVTZ basis set for the reliable prediction of the 11 B and 1 H NMR spectra of the boron-hydrogen species, and also for the reliable prediction of their IR and Raman spectra while taking into account the anharmonicity of their molecular vibrations.

Two reactive hydride composite systems, Ca(BH4)2–NaNH2 and Mg(BH4)2–NaNH2, were systematically studied by in situ synchrotron radiation powder diffraction, in situ Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry coupled with mass spectrometry. Metathesis reactions between the amides and borohydrides take place in both systems between 100 and 150 °C yielding amorphous materials with the proposed composition M(BH4)(NH2). Simultaneously, a fraction of NaNH2 decomposes to Na3N and ammonia via a complex pathway. The main gas released under 300 °C is ammonia for both systems, while significant amounts of hydrogen are released only above 350 °C.

The closoborane and their derivatives have attracted high interest due to their superionic conductivity. Very recently, high ionic conductivities have been reported for compounds containing the closoborane ion B12H122-. In this work, we address halogen-substituted ions B12H nX(12- n)2- ( n = 0-3, 6, 9-12 and X = F, Cl, Br) using DFT calculations to probe the structures, the chemical stability, and the electrochemical stability, as well as spectroscopic properties in view of potential future applications. Considering the theoretical reaction n/12 B12H122- + (12- n)/12 B12X122- → B12H nX(12- n)2-, it appears that for X = Cl and Br the compounds with n = 6 are stabilized by about 100 kJ/mol. The calculation of the vertical detachment energy (which is indirectly related to the electrochemical stability) shows an increasing stability with increasing halogen content. These results suggest that, for practical applications, it is likely that a partially halogenated ion offers the best compromise. The calculations of vibrational properties and NMR chemical shifts also reveal several systematic trends, which are discussed and compared to available literature values.

We report a robust methodology based on linear sweep voltammetry to determine experimentally the electrochemical oxidative stability of hydroborate-based solid-state electrolytes for all-solid-state batteries. To accelerate kinetics and improve the sensitivity to decomposition, we explore different solid-state electrolyte/carbon composites and employ a low scan rate of 10 μV s–1. Using LiBH4 as a model system, we show that proper selection of the conductive carbon and its ratio in the composite are important for an accurate determination of the intrinsic oxidative stability. This method is robust with respect to the choice of the current collector material and the ionic conductivity of the solid-state electrolyte. The measured oxidative stability of LiBH4 of 2.0 V vs Li+/Li is in good agreement with the value predicted by first-principles calculations. The irreversible electrochemical decomposition of LiBH4 outside the oxidative stability limit is independently confirmed by galvanostatic cycling. We apply this method to reassess the electrochemical oxidative stability of selected, highly conductive hydroborate-based solid-state electrolytes, including Li2(CB9H10)(CB11H12), Na3(BH4)(B12H12), Na4(B12H12)(B10H10), and Na4(CB11H12)2(B12H12), and emphasize the necessity of selecting cathode materials for all-solid-state batteries based on the accurate understanding of the oxidative stability of the solid-state electrolytes.

[Image: see text] The thermal decomposition of boron–hydrogen compounds is complex and multistep and involves the formation of various intermediates. An accurate description of the thermodynamics of the reactants, products, and intermediates is required for an in-depth understanding of their reactivity. In this respect, we have proceeded to the accurate determination of the key thermodynamic functions (ΔH(T), S(T), and C(P)(T)) of 44 isolated B–H molecular species involved in the decomposition of B–H solids, with the inclusion of anharmonic effects. An excellent agreement is observed with available experimental data. We report the analytic expressions of these functions obtained by fitting them with NASA functions in the 200–900 K temperature range. Because the vibrational spectra of these species are their fingerprints, we also report the predicted IR and Raman spectra. The calculated anharmonic spectra show an excellent agreement with experiments and allow for a clear-cut identification of fundamentals, combinations, and overtones.

The conduction mechanism of Na2(B12H12)0.5(B10H10)0.5, a particularly promising solid-state electrolyte for sodium-ion batteries, is elucidated. We find from electrochemical impedance spectroscopy that the temperature-dependent conductivity is characterized by three distinct regimes of conductivity. In the first regime, at temperatures below −50 °C, conductivity remains low before a glasslike transition identified by X-ray diffraction and calorimetry causes a faster increase of sodium conductivity through site disordering. The second regime of faster diffusion above −50 °C is characterized by an apparent activation energy of 0.6 eV, higher than expected from the local microscopic barrier of 0.35 eV observed by, e.g., 23Na nuclear magnetic resonance spin-lattice relaxation. This mechanism of so-called correlated ion diffusion originates from the coupling of the cation and anion motion due to short-range ion–ion interactions combined with background energy fluctuations, which we can associate through quasi-elastic neutron scattering experiment to fast librations of the anions. In the third regime, at temperatures above 70 °C, the thermal energy increases above the background energy fluctuations and the activation energy decreases to 0.34 eV, reflecting the local energy barrier for noncorrelated ion diffusion. We discuss the link between this behavior and the different frustrations responsible for the high conductivity of closo-borate electrolytes and show that our interpretation can also explain the complex conductivity behavior observed in related compounds.

The use of the Sm2+ luminescence properties in numerous applications appeals for a better understanding of its electronic structure. This work compares luminescence data and crystal field parameters from 31 Sm2+-containing compounds to assess the effects of the crystal field on its energy levels. In particular, the relationship between the 5D0-7F0 and 5D0-7F1 transition energies is analyzed and compared with previously published data for the isoelectronic Eu3+. It appears that for Sm2+, in contrast to Eu3+, the energy of the 5D0 state cannot be considered to be constant and implies the involvement of an extra state (presumably the 4f55d1 level) in the mixing of the 4f6 states. On the other side, the total crystal field strength is correlated to the splitting of the 7F1 states for both Sm2+ and Eu3+ in lower symmetry environments. The plot of the 5D0-7F0 energy as a function of the 7F1 splitting clearly evidences the mixing of the 4f6 state with the environment-sensitive 4f55d1 state for Sm2+, which is finally confirmed by the discrepancy of the ratio between the 5D1 and 7F1 splittings from its theoretical value in the absence of any mixing with the 4f55d1 state.

All-solid-state batteries (ASSBs) promise higher power and energy density than batteries based on liquid electrolytes. Recently, a stable 3 V ASSB based on the super ionic conductor (1 mS cm-1 near room temperature) Na4 (B12 H12 )(B10 H10 ) has demonstrated excellent cycling stability. This study concerns the development of a five-step, scalable, and solution-based synthesis of Na4 (B12 H12 )(B10 H10 ). The use of a wet chemistry approach allows solution processing with high throughput and addresses the main drawbacks for this technology, specifically, the limited electrode-electrolyte contact and high cost. Moreover, a cost-efficient synthesis of the expensive precursors Na2 B10 H10 and Na2 B12 H12 is also achieved through the same process. The mechanism of the reactions is investigated and two key parameters to tune the kinetics and selectivity are highlighted: the choice of counter cation (tetraethylammonium) and solvent.

closo-Borates, such as Na2B12H12, are an emerging class of ionic conductors that show promising chemical, electrochemical and mechanical properties as electrolytes in all-solid-state batteries. Motivated by theoretical predictions, high-pressurein situpowder X-ray diffraction on Na2B12H12was performed and two high-pressure phases are discovered. The first phase transition occurs at 0.5 GPa and it is persistent to ambient pressure, whereas the second transition takes place between 5.7 and 8.1 GPa and it is fully reversible. The mechanisms of the transitions by means of group theoretical analysis are unveiled. The primary-order parameters are identified and the stability at ambient pressure of the first polymorph is explained by density functional theory calculations. Finally, the parameters relevant to engineer and build an all-solid-state battery, namely, the bulk modulus and the coefficient of the thermal expansion are reported. The relatively low value of the bulk modulus for the first polymorph (14 GPa) indicates a soft material which allows accommodation of the volume change of the cathode during cycling.

The persistent phosphorescence and thermoluminescence of SrAl2O4:Eu2+:Dy3+ is reported for a variety of different excitation wavelengths and excitation temperatures, to provide new insights in the mechanism of the trapping and detrapping. These measurements reveal that the trapping is strongly dependent on the wavelength and temperature. First, with increasing loading temperature, the thermoluminescence peak shifts to lower temperatures which corresponds to a change of trap population. Secondly, the integrated thermoluminescent intensity increases with increasing loading temperature. All wavelength and temperature dependent experiments indicate that the loading of the traps is a thermally activated processes. Utilizing different wavelengths for loading, this effect can be enhanced or reduced. Furthermore excitation with UV-B-light reveals a tendency for detrapping the phosphor, reducing the resulting thermoluminescent intensity and changing the population of the traps.

Persistent luminescence of SrAl2O4:Eu2+ has attracted considerable attention due to their high initial brightness, long-lasting time and excellent thermal stability. Here the influence of boric acid on the persistent luminescence and thermal oxidation resistance of SrAl2O4:Eu2+ was investigated in detail. Crystal structural analysis and scanning electron microscopy revealed that with the addition of boron, the unit cell volume decreased and the morphology of the particles became more irregular with sharp edges. Thermogravimetric analysis showed better thermal oxidation resistance accompanied by a change in oxygen vacancy concentration when boron acid is used. Photoluminescence spectra and afterglow decay curves confirm an improved afterglow performance for boron-added SrAl2O4:Eu2+. Thermoluminesence allowed monitoring the changes in the trap states due to the presence of B. Our results imply that the substantial improvement of afterglow performance and the thermal stability in SrAl2O4:Eu2+ can be attributed to the incorporation of boron into the aluminate network.

B 12 H 12 2 − can be formed during the thermal decomposition of metal borohydrides ( M ( B H 4 ) x ) . Halogen ions such as fluoride or chloride can contribute to destabilize the B H 4 − ions. Hydride and fluoride mixed species like B 12 H n F ( 12 − n ) 2 − will be probable products after hydrogen release from mixed boro-hydride-fluoride ( B H x F ( 4 − x ) − ) or borohydride-borofluoride systems ( B H 4 − , B F 4 − ). Various number of isomers are possible for B 12 H n F ( 12 − n ) 2 − (n = 2–11). DFT calculations were performed on isolated ions of all the possible isomers for (n = 0–3, 9–12), using B3LYP functionals and 6-31G(d,p) basis set. Relative stability, vibrational and NMR spectroscopy of these isomers are discussed and compared with available experimental data.

A rational molecular design strategy for carbazole–oxadiazole based bipolar host materials was developed to improve the device efficiency of blue phosphorescent organic light-emitting diodes (PHOLED). Steric effects of strategically placed methyl groups led to an increase of triplet energies (o-2MPCzPOXD: 2.66 eV and o-3MPCzPOXD: 2.73 eV versus the initial host material o-PczPOXD: 2.62 eV) while less pronouncedly affecting singlet energies and, therefore, retaining low driving voltages, high power efficiencies and remarkably low efficiency roll-offs in PHOLEDs. The maximum quantum efficiencies (EQE) for blue devices (FIrpic) were significantly raised for o-2MPCzPOXD (13.6%) and o-3MPCzPOXD (11.5%) versus o-PCzPOXD (9.0%) although yielding comparable values for green devices (Ir(ppy)3; 12.9% and 15.4% versus 13.2%). Supported by theoretical calculations a structure–property relationship was established from photo-physical properties, PHOLED performance measurements and structural characterization from single crystal data.

The synthesis of 10 novel P-substituted dithienophosphole oxide compounds applying phenylcarbazole and indolocarbazole donors is presented. Based on photo-physical and theoretical investigations, the study reveals that the pyramidal geometry of the phosphorus allows for the synthesis of charge transfer materials by introducing strong exocyclic donor groups but suppresses intramolecular charge transfer below a certain donor strength threshold, which is an appealing structural feature for the design of donor–acceptor materials. The triplet energies of the phenylcarbazole based compounds are in the range of 2.49–2.65 eV, sufficiently high for potential applications as host materials in PhOLEDs. By contrast, the introduction of indolocarbazole, the weakest employed donor, yields materials exhibiting a significantly higher triplet energy of up to 2.87 eV and a remarkably low singlet–triplet splitting (0.18 eV). In addition an interesting example of an intramolecular electronic through-space interaction has been observed for the ortho-linked phenylcarbazole derivative.

The absorption spectra of Sm2+ doped in MFX (M=Sr, Ba; X=Cl, Br) crystals were studied within the range of 20,000–35,000 cm−1 as a function of temperature and host. The absorption bands observed were described with a simple model developed by Wood and Kaiser using group theory. The temperature and host dependence on the 7F0→5D3 Fano resonance lines were investigated. BaFCl:Sm2+ system showed a “normal” 7F0→5D3 transition at 4 K in spite of similar crystal structure and absorption profile with other MFX hosts. New Fano resonances were observed in the absorption spectra at higher energies (23,000–25,000 cm−1) for all MFX:Sm2+ systems at 4 K which persist up to room temperature. Preliminary energy level calculation showed that these resonance lines involve the interaction between higher excited 5LJ states of 4f6 configuration and 4f55d1 configuration.

Europium-doped crystalline Ba7F12Cl2 phosphors have been prepared at temperatures between 650 and 900 °C using alkali chloride fluxes, yielding both disordered (with the incorporation of small amounts of Na) and ordered crystal modifications. The white emission spectrum excited in the near UV consists roughly of two broad emission bands at about 450 and 590 nm, as well as weak sharp Eu2+ 4f–4f emission bands around 360 nm. The incorporation of Eu2+ is further studied using EPR spectroscopy on single crystals and reveals a significant zero field splitting. The emission spectrum can be significantly tuned by varying the excitation wavelength between 300 and 390 nm. Fine tuning may also be achieved by chemical substitutions to form Ba7–xMyF12Cl2–zBrz (M = Na, Ca, Eu). Quantitative measurements of the light produced using commercial near UV LEDs show that the color temperature ranges between 4000 and 9700 K with CIE chromaticity coordinates close to the ideal values of x = y = 0.333. The best color rendering index (CRI) found was 0.83 and the highest light to light conversion yield was 171 lm/W. These results show that the title compound is a very promising candidate for white light generation using near UV LED excitation.

Copyright © 2014 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Hydrolysis of metal borohydrides in the presence of CO2 has not been studied so far although carbon dioxide contained in air is known to accelerate hydrogen generation. KBH4 hydrolysis promoted by CO2 gas put through an aqueous solution was studied by timeresolved ATR FTIR spectroscopy showing a transformation of BH4 into B4O5(OH)4 2 and a drastically accelerated hydrogen production which can be completed within minutes. This process can be used to produce hydrogen on board from exhaust gases (CO2 and H2O). We found a new intermediate K9[B4O5(OH)4]3(CO3)(BH4)·7H2O forming upon hydrolysis on air via a slow adsorption of the atmospheric CO2. The same intermediate can be crystallized from partly hydrolyzed solutions of KBH4 + CO2 but not from the fully reacted sample saturated with CO2. This phase was studied by single crystal and powder X ray diffraction DSC TGA Raman IR and elemental analysis all data are fully consistent with the presence of the three different anions and of the crystallized water molecules. Its crystal structure is hexagonal space group P 62c with lattice parameters a = 11.2551(4) c = 17.1508(8) A° Formation of the intermediate produces 16 mol of H2 per mole of adsorbed CO2 and thus is very efficient both gravimetrically and volumetrically. It allows also for an elimination of carbon dioxide from exhaust gases.

The compound Ba5I2O12 was synthesized by heating a precipitate of dissolved Ba(OH)2·8H2O and H5IO6. Rb2O was added to increase the crystallite size. The crystal structure was determined from conventional laboratory X-ray diffraction data by using a real-space structure solution approach followed by a Rietveld refinement. No constraints on positions were used. The structure analysis gave an orthorhombic symmetry with a = 19.7474(2) A, b = 5.9006(1) A and c = 10.5773(1) A. The final RBragg value in space group Pnma (62) was 1.0 %. The structure can be described by layers of a metal and iodine arrangement forming almost pentagonal holes. Raman measurements were correlated with the two IO6 octahedra. Two further barium periodate patterns were observed and indexed.

We report on a comprehensive study of the magnetization, resistivity and heat capacity on the single crystals of Ce 2 RhGa 12 synthesized using Ga flux. Single crystal X-ray diffraction data confirm the tetragonal Pb/nbm structure of Ce 2 RhGa 12 , which is isostructural to Ce 2 PdGa 12 . Ce 2 RhGa 12 orders antiferromagnetically at T N = 3.5 K and exhibits anisotropic magnetic behavior, inferred from the magnetization and resistivity data, taken along the two principal crystallographic directions of the crystal, viz., along [1 0 0] and [0 0 1]. The anisotropic magnetic response of Ce 2 RhGa 12 establishes [0 0 1] as the easy axis of magnetization, and a weak meta-magnetic transition is also observed in the magnetic isotherm at 2 K along the same axis. A sharp peak in specific heat signals the bulk antiferromagnetic transition at T N = 3.5 K, which shifts to lower temperatures in low applied fields. The electrical resistivity along the two directions shows metallic behavior from 300 K down to 1.8 K and establishes Ce 2 RhGa 12 as a normal, trivalent cerium compound.

The vapor pressure and molecular weight of effusing vapors of α, β, and amorphous Mg were determined by Torsion-effusion gravimetric method, under dynamic vacuum. A Cahn balance in the system yielded the rate of the weight loss. Molecular weights measured revealed if the effusion was congruent or there was disproportionation. The vaporization behavior of crystalline Mg(BH42, was measured up to 533 K at pressures of ∼10-5 torr. It was found that Mg(BH4)2 disproportionates to form predominantly H2 gas (∼95%) with a small amount of Mg(BH4) (∼5%) in the gas phase. The combined average molecular weight measured is 4.16 g/mol. The equations for vapor pressures for crystalline Mg(BH4)2 are given by: log PT (bar) = 9.2303 - 7286.2/T, logPMg(BH4)2(bar)=8.2515-7286. 2/T, and logPH2(bar)=9.1821-7286.2/T. The partial pressures of the gaseous species were determined as PMgBH4)2PT=0.105 and PH2(g)PT=0.895. Enthalpies of vaporization for the effusing gases were calculated to be ΔH = +558.0 kJ/mol H2 and ΔH = +135 kJ/mol Mg(BH4)2. The standard Gibbs free energy changes, ΔG (kJ/mol), for the complete decomposition reaction (Mg(BH4)2(s) → Mg (s) + 2B(s) + 4H2(g)), sublimation reaction (Mg(BH4)2(s) → Mg(BH4)2(g)) and the disproportionation reaction for Mg(BH4)2 are reported in this paper. The decomposition pathway of amorphous Mg(BH4) 2 was also carried out between 388.2 K and 712.8 K showing multistep decomposition of a-Mg(BH4)2 Different reaction products were obtained depending on the method used in the vaporization experiment. The behavior of the amorphous Mg(BH4)2(s) is very different from those for the two crystalline phases (α and β). The vapor pressure behavior and thermodynamics of vaporization of different phases of Mg(BH4)2 are presented. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights.

The emission lifetime of Sm2+ ions doped in MFX (M=Ba, Sr; X=Br, I) crystals was investigated as a function of pressure and temperature. The decay of the 5DJ(J=0,1,2) levels showed single exponential relaxation. The analysis of these experiments yielded the position of the lowest 4f55d1 state as well as non-radiative rate constants. These values were compared with those for Sm2+ doped in other matlockite host crystals. The single exponential decrease of the 5D0,1 lifetime as a function of pressure was described considering the increased radiative decay rates of these 5D0,1 levels through electronic mixing between the 4f55d1 and 5DJ states.

This work deals with the synthesis and crystal structure study of new bismuth oxo-arsenates and their homologous oxo-phosphates: Bi6ZnO7(AsO4)2vs. Bi6ZnO7(PO4)2 and Bi3.667Cd3O4(AsO4)3vs. Bi3Cd4O4(PO4)3. Their crystal structures were solved using single crystal X-ray diffraction. These are two other examples of crystal structures built on ribbon-like polycations formed of the linkage of oxo-centered O(Bi,M)4 tetrahedra sharing edges and surrounded by isolated XO4 groups (X = As or P), where the O(Bi,M)4 units are derived from the fluorite topology structure. Dealing with Bi6ZnO7(PO4), its acentric space group was confirmed by preliminary second harmonic generation (SHG). The P/As substitution led to a centrosymmetric space group due to local reorientation of oxo-anions. This is strongly related to steric effects between AsO4 (d As–O = 1.6–1.7 A) and PO4 (d P–O = 1.4–1.5 A). Concerning Bi3.667Cd3O4(AsO4)3 and Bi3Cd4O4(PO4)3, they show a second example of the reorientation of the XO4 groups depending of the X chemical nature. Finally, we present an original topology of oxo-centered units obtained with Bi5KO5(AsO4). The photoluminescence properties of Bi5KO5(AsO4) and Bi6ZnO7(AsO4)2 were also investigated. The first one emits at room temperature in the reddish-orange range (single band peak at 615 nm assigned to the Bi3+: 3P1 → 1S0 transition) whereas the second exhibits a weak emission in the green range (peak at 530 nm). Its intriguing temperature dependence is discussed in the paper.

Lithium amideborohydrides Li[BH4](1x)[NH2](x) possess liquid-like Li superionic conductivity at nearly ambient temperature. The fast Li+ diffusion facilitated by the localized motions of the anions is proposed to occur through a network of vacant tetrahedral sites, acting as conduction channels. To study the reorientational dynamics of the anions, we have performed quasielastic neutron scattering experiments on samples with different compositions (x = 2/3, 0.722, 0.737, 3/4) over a broad temperature and time range. To unambiguously disentangle the contributions of the two species, [BH4](-) and [NH2](-), we took advantage of deuterium labeling and could clearly demonstrate that the quasielastic broadening is mainly determined by the [BH4](-) reorientations. With the help of a newly developed model, supported by ab initio molecular dynamics calculations, we have identified three relaxation components, which account for generally anisotropic C-3-rotations of the [BH4](-) tetrahedra including jumps by a small angle from the equilibrium position.

We report the DFT study of the vibrational spectroscopy properties of Mg(B3H8)2, a potential intermediate in the decomposition of Mg(BH4)2, as well as those of CB11H12− and CB9H10−, whose salts can exhibit high ionic conductivities. Because the inclusion of anharmonicity is key to the accurate description of the vibrational properties of BH species [D. Sethio, L. M. Lawson Daku, H. Hagemann. Int. J. Hydrogen Energy, 41 (2016) 6814], the calculations were performed both in the harmonic and in the anharmonic approximation. The IR and Raman spectra of Cs(CB11H12) and Na2(B10H10) have also been measured. The calculated and experimental spectra are in good agreement. A comparative analysis of the vibrational spectroscopy properties is made for B3H8− and Mg(B3H8)2, B12H122− and CB11H12−, and for B10H102− and CB9H10−.

Alkaline or alkaline earth octahydrotriborate M(B3H8)x and dodecahydro-closo-dodecaborate MxB12H12 (M = Li, Na, Mg or Ca with x = 1 or 2) have recently attracted a lot of interest for hydrogen storage and solid electrolyte applications. Nevertheless, their syntheses are still a roadblock for large scale applications. In this paper we propose a novel approach for their syntheses starting from the cheapest borohydride NaBH4. The process involves first the solvothermal synthesis of tetrabutylammonium octahydrotriborate (C4H9)4NB3H8 (TBAB3H8) being the basis for the syntheses of the others boranes. Starting from TBAB3H8, we have synthesized pure and unsolvated NaB3H8 by salt metathesis reaction with sodium tetraphenylborate. Then, we have successfully obtained Na2B12H12 by solvothermal decomposition of NaB3H8. This approach has shown to be quantitative and reproducible, which could lead to the development of these boranes in real life applications.

A new sodium-yttrium borohydride-chloride, NaY(BH 4) 2Cl 2, is obtained by a combination of mechanochemical synthesis and annealing of NaBH 4-YCl 3 mixtures and is characterized by in-situ synchrotron radiation X-ray powder diffraction, density functional theory, thermal analysis and vibrational spectroscopy. Several simultaneous and coupled reactions occur during the synthesis, also yielding Na 3YCl 6 and Na(BH 4) 1-xCl x besides the title compound. The polymeric pseudo-orthorhombic crystal structure of NaY(BH 4) 2Cl 2 (space group P2/c) is built of edge- and corner-sharing octahedral coordination polyhedra of yttrium (4Cl + 2BH 4) and sodium (2Cl + 4BH 4). The structure is isomorphous to the high temperature polymorph of NaYCl 4. The BH 4 units in NaY(BH 4) 2Cl 2 are located only on the larger of the two independent anion sites in NaYCl 4. Density functional theory optimization of the experimental structure suggests that the BH 4 units act as η 3-ligands (face-sharing) towards yttrium and η 1-ligands (corner-sharing) towards sodium. Raman spectroscopy confirms this BH 4 configuration. NaY(BH 4) 2Cl 2 decomposes at ∼300°C under formation of Na 3YCl 6, while the latter compound at higher temperatures reacts with Na(BH 4) 1-xCl x to form NaCl and possibly amorphous products. The reactions are associated with mass losses of 2.62 and 3.78 wt% for the NaBH 4-YCl 3 (3:1) and (4:1) samples, respectively. © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

To study the reorientational motion of BH4 groups in β and γ phases of Mg(BH4)2 and in α and β phases of Ca(BH4)2, we have performed nuclear magnetic resonance (NMR) measurements of the 1 H and 11 B spin− lattice relaxation rates in these compounds over wide ranges of temperature and resonance frequency. It is found that at low temperatures the reorien- tational motion in β phases of Mg(BH4)2 and Ca(BH4)2 is considerably faster than in other studied phases of these alkaline-earth borohydrides. The beha- vior of the measured spin−lattice relaxation rates in both β phases can be satisfactorily described in terms of a Gaussian distribution of activation ener- gies Ea with the average Ea values of 138 meV for β-Mg(BH4)2 and 116 meV for β-Ca(BH4)2. The α phase of Ca(BH4)2 is characterized by the activation energy of 286 ± 7 meV. For the novel porous γ phase of Mg(BH4)2, the main reorientational process responsible for the observed spin−lattice relaxation rate maximum can be described by the activation energy of 276 ± 5 meV. The barriers for reorientational motion in different phases of alkaline-earth borohydrides are discussed on the basis of changes in the local environment of BH4 groups.

Single crystals of Ce2RhGa12 have been synthesized using Ga flux and their structure was determined by single-crystal X-ray diffraction. Ce2RhGa12 crystallizes in the tetragonal space group P4/nbm (No. 125), and is isostructural to Ce2PdGa12, with Z = 2 and lattice parameters a = 6.0405 A and c = 15.706 A. Data were collected at the Swiss Norwegian Beam Line at the European Synchrotron Facility, Grenoble, France. Laue diffraction was carried out to confirm the quality of the single crystal and showed well-defined spots and tetragonal symmetry.

To study the reorientational motion of BH4 groups in the low-temperature (α) phase of Mg(BH4)2, we have performed nuclear magnetic resonance (NMR) measurements of the 1H and 11B spin−lattice relaxation rates in this compound over wide ranges of temperature (82−443 K) and resonance frequency (14−90 MHz for 1H and 14−28 MHz for 11B). It is found that the thermally activated reorientational motion in α-Mg(BH4)2 is characterized by a coexistence of at least three jump processes with strongly differing activation energies. Taking into account the anisotropy of the local environment of BH4 groups in α-Mg(BH4)2, these jump processes can be attributed to different types of reorientation. The nearly linear coordination of BH4 groups by two Mg atoms suggests that the fastest jump process corresponds to the rotation around the 2-fold axis connecting B and two Mg atoms, whereas the slowest process is associated with the rotation around two other 2-fold axes perpendicular to the Mg−B−Mg line.

Metal borohydrides are potential materials for solid-state hydrogen due to their high gravimetric and volumetric hydrogen densities. Among them, Ca(BH4)2 is particularly interesting because of the predicted suitable thermodynamic properties. In this work, we investigate a new synthesis route using high-pressure reactive ball milling. Starting from CaH2 and CaB6 with a TiCl3 or TiF3 as additive, a reaction yield of 19% is obtained after 24 h milling at room temperature and 140 bar H2. The presence of Ca(BH4)2 is confirmed by the presence of the stretching mode of the [BH4]- group in the infrared spectra of the as-milled samples. Using in situ XRD, we observe the recrystallisation of a poorly crystallised Ca(BH4)2 phase present after milling. The reversible decomposition/formation of Ca(BH4)2 is obtained with higher yield (57%) using higher temperature and TiF3 as additive but not with TiCl3 despite its similar electronic structure. The differences observed using different additives and the influence of the anion are discussed. © 2009 Elsevier B.V. All rights reserved.

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.

A new alkaline transition-metal borohydride, NaSc(BH4)(4), is presented. The compound has been studied using a combination of in situ synchrotron radiation powder X-ray diffraction, thermal analysis, and vibrational and NMR spectroscopy. NaSc(BH4)(4) forms at ambient conditions in ball-milled mixtures of sodium borohydride and ScCl3. A new tertiary chloride Na3ScCl6 (P2(1)/n, a = 6.7375(3) angstrom, b = 7.1567(3) angstrom, c = 9,9316(5) angstrom, beta = 90.491(3)degrees, V = 478.87(4) angstrom(3)), isostructural to Na3TiCl6, was identified as an additional phase in all samples. This indicates that the formation of NaSc(BH4)(4) differs from a simple metathesis reaction, and the highest scandium borohydride yield (22 wt %) was obtained with a reactant ratio of ScCl3/NaBH4 of 1:2. NaSc(BH4)(4) crystallizes in the orthorhombic crystal system with the space group symmetry Cmcm (a = 8.170(2) angstrom, b = 11.875(3) angstrom, c = 9.018(2) angstrom, V = 874.9(3) angstrom(3)). The Structure of NaSc(BH4)(4) consists of isolated homoleptic scandium tetraborohydride anions, [Sc(BH4)(4)](-), located inside slightly distorted trigonal Na-6 prisms (each second prism is empty, triangular angles of 55.5 and 69.1 degrees). The experimental results show that each Sc3+ is tetrahedrally Surrounded by four BH4 tetrahedra with a 12-fold coordination of H to Sc, while Na+ is surrounded by six BH4 tetrahedra in a quite regular octahedral coordination with a (6 + 12)-fold coordination of H to Na. The packing of Na+ cations and [Sc(BH)(4))(4)](-) anions in NaSc(BH4)(4) is a deformation variant of the hexagonal NiAs structure type. NaSc(BH4)(4) is stable from RT up to similar to 410 K, Where the compound melts and then releases hydrogen in two rapidly occurring steps between 440 and 490 K and 495 and 540 K. Thermal expansion of NaSc(BH4)(4) between RT and 408 K is anisotropic, and lattice parameter b shows strong anomaly close to the melting temperature.

Specifically labeled NaBD(3)H has been synthesized and characterized using X-ray diffraction, NMR, and vibrational spectroscopy. The isotopic purity of the compound, as estimated from NMR spectra, was found to be about 85% with the compound NaBD(2)H(2) as the second product. IR spectra confirm the relatively strong intensity of the single B-H stretching mode predicted from DFT calculations. Anharmonic DFT calculations show that for the BD(3)H(-) ion Fermi resonances with the single B-H stretching mode are very limited, making this mode a promising structural probe for complex borohydrides which can be prepared by metathetical reactions.

We have demonstrated experimentally by Raman analysis that 1a exists as a mixture of ttt/cct conformers at 22°C in liquid or CCl4 solution, thus contrasting with the initial IR, NMR and X-ray analyses, which were strongly in favour of (ttt)-1a. The global stereoelectronic stabilization is ca. 4.0-4.2 kcal/mol for both parallel N lone pairs (lp) in (cct)-1a, based on a ΔH of 0.75 kcal/mol (±10%), as measured by Raman spectroscopy from 22 to 90°C, as well as the roughly estimated MM2 MeNHEt and MeNHCH2NH2 gauche interactions. DFT calculations using B3LYP/6-31G* yield a standard ΔH value of 1.04 kcal/mol, in good agreement with the experiment, and predict a ttt/cct ratio of ca. 77:23 at 25°C. Broadening of the 13C-NMR signals was observed in either CCl4 or CS2 or even CDCl3 solutions between -20 and -40°C.

A series of mixed crystals with general formula Ba7-xNayF12Cl2-zBrz in the ordered modification (space group P-6) has been studied by single crystal x-ray diffraction. Depending on synthesis conditions, the disorder in the channels (i.e. occupation of 0 0 z sites) can be changed. The disorder is found to be correlated with the refined Na content, and its effect on Ba-Cl(Br) bond length is discussed.

SrMgF4 was prepared by precipitation in aqueous solution. Alkaline earth metal acetates and ammonium fluoride were used as precursors. After drying and annealing the samples at different temperatures and times, single phase SrMgF4 was obtained. By varying the annealing conditions, the mean crystallite size could be adjusted. Furthermore, the thermally treated samples displayed UV-excited intensive broad band luminescence in the visible region. The emissions colour and intensity can be adjusted by the tempering conditions. X-Ray diffraction, TEM-microscopy, fluorescence and IR-spectroscopy were used for analysis.

We have recently prepared solid solutions of Ba∼6.3Ca∼0.7F12Cl2−xBrx with x ranging from 0 to 2. In this work, the synthesis and single crystal X-ray structure of calcium-free crystals of Ba∼6.9Na∼0.2F12Br0.6Cl1.4 (space group P63/m, a = 10.6024(10), c = 4.2034(4) A), Ba∼6.9Na∼0.2F12Br1.4 Cl0.6 (space group P63/m, a = 10.6155(9), c = 4.2355(4) A) and Ba∼6.9Na∼0.2Br1.32Cl0.68F12 (space group P63/m, a = 10.6218(9), c = 4.2284(4) A) are reported. These crystals systematically present additional electron density at the 0 0 0.25 position which is associated with the presence of small, but significant amounts of Na+ ions in the crystal.

Single crystal dixanthinium tetrachlorozincate has been grown from dilute chloridric acid. Polarized Raman spectrum of the single crystalline sample, FT-Raman and FT-IR spectra of the polycrystalline samples have been examined and the bands assigned to the appropriate modes predicted by a factor group analysis for the space group Pmn21. The crystal structure has been confirmed by powder XRD measurements.

The crystal structure of the disordered modification of Ba7F12Cl2 has been carefully re-examined on several new crystals prepared under different conditions of synthesis. All single crystal structure refinements reveal a residual electron density of 3 e-/Å3 in the 0,0,0 position which is explained by the introduction of a small amount of sodium ions in the crystal. The title compound transforms from a disordered to an ordered modification at 800 °C. New structural data show a change in space group from P63/m to P6. During this process, a slight chemical change and the formation of nano-channels in the crystals is observed by electron microscopy. These changes were further studied by electron microprobe analysis, by spectroscopic methods and thermal analysis.