X-ray Powder Diffraction Experiments Research Articles

Effect of specimen displacement in X-ray powder diffraction measurements with laboratory diffractometers

The effect of specimen displacement in X-ray powder diffraction experiments with laboratory diffractometers has been revisited and new expressions have been derived for several commonly used experimental configurations, including Bragg–Brentano parafocusing geometry and flat-plate transmission geometry. The results presented in this work allow the analysis of data from samples with relatively large displacements. This may open the possibility to study samples with dimensions that are difficult to accommodate with the sample-handling capabilities of standard laboratory diffractometers.

Nucleation, crystal growth, XRD, optical, electrical, PC, SEM, SHG and Z-scan analysis of LHPP for NLO and optical limiting application

High-quality organic L-histidinium 4-nitrophenolate 4-nitrophenol (LHPP) single crystals were grown using an aqueous solution. The crystals were grown using slow evaporation solution technique (SEST) at a temperature of 40°C using a constant temperature bath (CTB). Nucleation growth rates were monitored for various durations using an optical microscope. The crystalline perfection was confirmed through sharp, high-intensity diffraction peaks observed in the theoretical and experimental powder X-ray diffraction (PXRD) analysis, which also confirmed the monoclinic crystal structure with the noncentrosymmetric P21 space group. The crystallite size and strain were calculated using Williamson–Hall coefficient. Vibrational frequency assignments of LHPP were determined using FTIR spectroscopic analysis. Optical properties were studied using UV–Vis NIR spectroscopic studies, which showed that the crystals have very low absorption and high transmittance in the entire visible region. Additionally, the optical energy bandgap (Eg) was calculated and found to be 6.15[Formula: see text]eV. Luminescence properties were studied using fluorescence (FL) analysis. Dielectric investigations were subjected to varying frequencies to study the suitability of the crystal for transistor application. The positive photoconductive (PC) nature of the crystal was confirmed using photoconductivity studies to confirm suitability for photodetector devices that measure the intensity of light rays. Etching studies revealed the growth pattern and the formation of different kinds of etch pits. The surface morphology was studied using scanning electron microscopy (SEM) and electrochemical studies were also carried out. The relative second harmonic generation (SHG) efficiency of the material was also examined and found to be 1.34 times that of standard KDP. The optical limiting and higher-order nonlinear optical (NLO) properties of the grown crystals were studied by the [Formula: see text]-scan method using a Nd: YAG laser functioning at 532[Formula: see text]nm.

Temperature- and pressure-responsive photoluminescence in a 1D hybrid lead halide

Low-dimensional hybrid lead halides with responsive emissions have attracted considerable attention due to their potential applications in sensing. Herein, a new one-dimensional hybrid lead bromide CyPbBr3 (Cy = cytosine cation) was synthesized to explore its emission evolution in response to temperature and pressure. The compound possesses an edge-sharing 1D double-chain structure and emits warm white light across nearly the entire visible spectrum upon ultraviolet excitation. This emission arises from the self-trapped excitons and its broadband feature is attributed to the strong electron-phonon coupling as revealed by the variable-temperature photoluminescence experiments. Moreover, a 4.5-fold pressure-induced emission enhancement was observed at 2.7 GPa which is caused by the pressure suppressed non-radiative energy loss. Furthermore, in-situ powder X-ray diffraction and Raman experiments reveal the maxima of the emission enhancement is associated with a phase transition at the same pressure. Our work demonstrates that low-dimensional metal halides are a promising class of stimuli-responsive materials which could have potential applications in temperature and pressure sensing.

Universal simulation of absorption effects for X-ray diffraction in reflection geometry.

Analytical calculations of absorption corrections for X-ray powder diffraction experiments on non-ideal samples with surface roughness, porosity or absorption contrasts from multiple phases require complex mathematical models to represent their material distribution. In a computational approach to this problem, a practicable ray-tracing algorithm is formulated which is capable of simulating angle-dependent absorption corrections in reflection geometry for any given rasterized sample model. Single or multiphase systems with arbitrary surface roughness, porosity and spatial distribution of the phases in any combination can be modeled on a voxel grid by assigning respective values to each voxel. The absorption corrections are calculated by tracing the attenuation of X-rays along their individual paths via a modified shear-warp algorithm. The algorithm is presented in detail and the results of simulated absorption corrections on samples with various surface modulations are discussed in the context of published experimental results.

Photoresponsive silver nanowire nanoplatform for real-time drug delivery in non-small cell lung cancer therapy

In this study, we first successfully synthesized three different sizes and shapes of Ag nanowires (Ag NWs) using a polyol synthesis method. The size and morphology of the Ag NWs were controlled by the types of inorganic control agents in the reaction system (NaCl for 1, CuCl2 for 2, and FeCl3 for 3). The synthesized Ag NWs were characterized using scanning electron microscopy (SEM) and powder X-ray diffraction (PXRD) experiments. Subsequently, due to the favorable width of 1, we utilized it as an effective photosensitizer to construct a novel drug-loaded nanomaterial platform, namely 1-PLC@DOX (PLC stands for poly(ε-caprolactone), and DOX stands for Doxorubicin), to achieve on-demand drug release triggered by near-infrared (NIR) laser. The results indicate that the drug delivery system can achieve minimally invasive treatment of complex geometric defects. Under near-infrared irradiation, 1-PLC@DOX can heat up to 53.6 °C within 15 min, showing a unique heating platform on the heating curve, with ideal photothermal stability and heating effect compared to other groups. By toggling near-infrared irradiation on or off, 1-PLC@DOX can exhibit a stair-step drug release curve, suggesting that on-demand control of drug release using near-infrared laser as a trigger is feasible. In vitro biological evaluations demonstrate that 1-PLC@DOX exhibits good biocompatibility and anti-tumor ability, significantly reducing the invasive ability of A549 cells on non-small cell lung cancer (NSCLC) cells, and at the same time inhibiting the proliferation of cancer cells by regulating the p53 signaling pathway to cause apoptosis.

Robustness of the pyrochlore structure in rare-earth A2Ir2O7 iridates and pressure-induced structural transformation in IrO2

A comprehensive study of the structural properties of the heavily investigated rare-earth A2Ir2O7 iridate series under extreme conditions is presented. From Pr2Ir2O7 to Lu2Ir2O7, the series is sufficiently covered by iridates with A = Pr, Sm, Dy, Ho, Er, Tm, Yb, and Lu; general trends and systematics within the series, including the understudied heavy-rare-earth members, are dependably followed. Temperature- and pressure-dependent synchrotron X-ray powder diffraction experiments reveal robustness of the pyrochlore structure throughout the series, down to 4 K and up to 20 GPa. The thermal expansivity of the pyrochlore lattice is determined, all falling in the Debye temperature range of θD = 360–420 K. The pressure compressibility shows a systematic increase of the bulk modulus with the rare-earth atomic number from K = 180–210 GPa. Combining the results of thermal measurements (Debye temperature) and pressure measurements (bulk modulus) enables us to determine the Grüneisen parameter of selected members and compare it to previous studies. Temperature and pressure evolution of the fractional coordinate of oxygen at 48f Wyckoff position, the sole free fractional coordinate in the crystal structure, is investigated and discussed regarding the antiferromagnetic ordering of the Ir magnetic moments. In addition to results on A2Ir2O7 iridates, the temperature and pressure evolution of the crystal structure of an IrO2 minority phase is followed. The tetragonal rutile-type structure is stable down to the lowest temperature. However, an application of pressure of approximately 15 GPa induces a structural transition: The tetragonal structure is orthorhombically distorted. The orthorhombic structure is still not fully stabilised at 20 GPa, and further distortion of the lattice (or subsequent structural transformations) is expected with increasing external pressure.

Optimizing the Sintering Conditions of (Fe,Co)1.95(P,Si) Compounds for Permanent Magnet Applications.

(Fe,Co)2(P,Si) quaternary compounds combine large uniaxial magnetocrystalline anisotropy, significant saturation magnetization and tunable Curie temperature, making them attractive for permanent magnet applications. Single crystals or conventionally prepared bulk polycrystalline (Fe,Co)2(P,Si) samples do not, however, show a significant coercivity. Here, after a ball-milling stage of elemental precursors, we optimize the sintering temperature and duration during the solid-state synthesis of bulk Fe1.85Co0.1P0.8Si0.2 compounds so as to obtain coercivity in bulk samples. We pay special attention to shortening the heat treatment in order to limit grain growth. Powder X-ray diffraction experiments demonstrate that a sintering of a few minutes is sufficient to form the desired Fe2P-type hexagonal structure with limited secondary-phase content (~5 wt.%). Coercivity is achieved in bulk Fe1.85Co0.1P0.8Si0.2 quaternary compounds by shortening the heat treatment. Surprisingly, the largest coercivities are observed in the samples presenting large amounts of secondary-phase content (>5 wt.%). In addition to the shape of the virgin magnetization curve, this may indicate a dominant wall-pining coercivity mechanism. Despite a tenfold improvement of the coercive fields for bulk samples, the achieved performances remain modest (HC ≈ 0.6 kOe at room temperature). These results nonetheless establish a benchmark for future developments of (Fe,Co)2(P,Si) compounds as permanent magnets.

Stimulus-Induced Dynamic Behavior Regulation of Flexible Crystals through the Tuning of Module Rigidity.

Introducing dynamic behavior into periodic frameworks has borne fruit in the form of flexible porous crystals. The detailed molecular design of frameworks in order to control their collective dynamics is of particular interest, for example, to achieve stimulus-induced behavior. Herein, by varying the degree of rigidity of ditopic pillar linkers, two isostructural flexible metal-organic frameworks (MOFs) with common rigid supermolecular building bilayers were constructed. The subtle substitution of single (in bibenzyl-4,4'-dicarboxylic acid; H2BBDC) with double (in 4,4'-stilbenedicarboxylic acid; H2SDC) C-C bonds in pillared linkers led to markedly different flexible behavior of these two MOFs. Upon the removal of guest molecules, both frameworks clearly show reversible single-crystal-to-single-crystal transformations involving the cis-trans conformation change and a resulting swing of the corresponding pillar linkers, which gives rise to Flex-Cd-MOF-1a and Flex-Cd-MOF-2a, respectively. Strikingly, a more favorable gas-induced dynamic behavior in Flex-Cd-MOF-2a was verified in detail by stepwise C3H6/C3H8 sorption isotherms and the corresponding in situ powder X-ray diffraction experiments. These insights are strongly supported by molecular modeling studies on the sorption mechanism that explores the sorption landscape. Furthermore, a consistency between the macroscopic elasticity and microscopic flexibility of Flex-Cd-MOF-2 was observed. This work fuels a growing interest in developing MOFs with desired chemomechanical functions and presents detailed insights into the origins of flexible MOFs.

Crystal structures of two new high-pressure oxynitrides with composition SnGe4N4O4, from single-crystal electron diffraction.

SnGe4N4O4 was synthesized at high pressure (16 and 20 GPa) and high temperature (1200 and 1500°C) in a large-volume press. Powder X-ray diffraction experiments using synchrotron radiation indicate that the derived samples are mixtures of known and unknown phases. However, the powder X-ray diffraction patterns are not sufficient for structural characterization. Transmission electron microscopy studies reveal crystals of several hundreds of nanometres in size with different chemical composition. Among them, crystals of a previously unknown phase with stoichiometry SnGe4N4O4 were detected and investigated using automated diffraction tomography (ADT), a three-dimensional electron diffraction method. Via ADT, the crystal structure could be determined from single nanocrystals in space group P63mc, exhibiting a nolanite-type structure. This was confirmed by density functional theory calculations and atomic resolution scanning transmission electron microscopy images. In one of the syntheses runs a rhombohedral 6R polytype of SnGe4N4O4 could be found together with the nolanite-type SnGe4N4O4. The structure of this polymorph was solved as well using ADT.

Functionalization and Structural Evolution of Conducting Quasi-One-Dimensional Chevrel-Type Telluride Nanocrystals.

Interfacing organic molecular groups with well-defined inorganic lattices, especially in low dimensions, enables synthetic routes for the rational manipulation of both their local or extended lattice structures and physical properties. While appreciably studied in two-dimensional systems, the influence of surface organic substituents on many known and emergent one-dimensional (1D) and quasi-1D (q-1D) crystals has remained underexplored. Herein, we demonstrate the surface functionalization of bulk and nanoscale Chevrel-like q-1D ionic crystals using In2Mo6Te6, a predicted q-1D Dirac semimetal, as the model phase. Using a series of alkyl ammonium (-NR4+; R = H, methyl, ethyl, butyl, and octyl) substituents with varying chain lengths, we demonstrate the systematic expansion of the intrachain c-axis direction and the contraction of the interchain a/b-axis direction with longer chain substituents. Additionally, we demonstrate the systematic expansion of the intrachain c-axis direction and the contraction of the interchain a/b-axis direction as the alkyl chain substituents become longer using a combination of powder X-ray diffraction and Raman experiments. Beyond the structural modulation that the substituted groups can impose on the lattice, we also found that the substitution of ammonium-based groups on the surface of the nanocrystals resulted in selective suspension in aqueous (NH4+-functionalized) or organic solvents (NOc4+-functionalized), imparted fluorescent character (Rhodamine B-functionalized), and modulated the electrical conductivity of the nanocrystal ensemble. Altogether, our results underscore the potential of organic-inorganic interfacing strategies to tune the structural and physical properties of rediscovered Chevrel-type q-1D ionic solids and open opportunities for the development of surface-addressable building blocks for hybrid electronic and optoelectronic devices at the nanoscale.

The Chemistry of Spinel Ferrite Nanoparticle Nucleation, Crystallization, and Growth.

The nucleation, crystallization, and growth mechanisms of MnFe2O4, CoFe2O4, NiFe2O4, and ZnFe2O4 nanocrystallites prepared from coprecipitated transition metal (TM) hydroxide precursors treated at sub-, near-, and supercritical hydrothermal conditions have been studied by in situ X-ray total scattering (TS) with pair distribution function (PDF) analysis, and in situ synchrotron powder X-ray diffraction (PXRD) with Rietveld analysis. The in situ TS experiments were carried out on 0.6 M TM hydroxide precursors prepared from aqueous metal chloride solutions using 24.5% NH4OH as the precipitating base. The PDF analysis reveals equivalent nucleation processes for the four spinel ferrite compounds under the studied hydrothermal conditions, where the TMs form edge-sharing octahedrally coordinated hydroxide units (monomers/dimers and in some cases trimers) in the aqueous precursor, which upon hydrothermal treatment nucleate through linking by tetrahedrally coordinated TMs. The in situ PXRD experiments were carried out on 1.2 M TM hydroxide precursors prepared from aqueous metal nitrate solutions using 16 M NaOH as the precipitating base. The crystallization and growth of the nanocrystallites were found to progress via different processes depending on the specific TMs and synthesis temperatures. The PXRD data show that MnFe2O4 and CoFe2O4 nanocrystallites rapidly grow (typically <1 min) to equilibrium sizes of 20-25 nm and 10-12 nm, respectively, regardless of applied temperature in the 170-420 °C range, indicating limited possibility of targeted size control. However, varying the reaction time (0-30 min) and temperature (150-400 °C) allows different sizes to be obtained for NiFe2O4 (3-30 nm) and ZnFe2O4 (3-12 nm) nanocrystallites. The mechanisms controlling the crystallization and growth (nucleation, growth by diffusion, Ostwald ripening, etc.) were examined by qualitative analysis of the evolution in refined scale factor (proportional to extent of crystallization) and mean crystallite volume (proportional to extent of growth). Interestingly, lower kinetic barriers are observed for the formation of the mixed spinels (MnFe2O4 and CoFe2O4) compared to the inverse (NiFe2O4) and normal (ZnFe2O4) spinel structured compounds, suggesting that the energy barrier for formation may be lowered when the TMs have no site preference.

Structural instability in LaNbO4 under compression

In this work, we report a high-pressure study on fergusonite-type LaNbO4. Powder x-ray diffraction and Raman spectroscopic experiments support the occurrence of a phase transition between 11 and 14 GPa. The transition takes place from a monoclinic fergusonite-type structure (space group I2/a) to another monoclinic structure (space group P21/c). The phase transition is reversible, and the high-pressure phase is isomorphic to the high-pressure phase of HoNbO4. The high-pressure phase remains stable up to 33.3 GPa, the highest pressure reached in the present measurements. Density-functional theory calculations found that in the pressure range of the studies; the high-pressure phase has a higher enthalpy than the low-pressure fergusonite phase. We propose that the high-pressure phase is metastable and it is observed because of non-hydrostatic conditions in the experiments. The pressure dependence of unit-cell parameters of the low-pressure phase and the room-temperature equation of state are reported. The pressure dependence of various Raman and IR frequencies as obtained from experiment and theory is also reported. For the fergusonite phase, we have also obtained the isothermal compressibility tensor, elastics constants, and elastic moduli.

Synthesis and structure refinement of the zinc hydroxide boracite: Zn3B7O13(OH)

Abstract The new zinc borate Zn3B7O13(OH) crystallizes trigonally in the space group R3c (no. 161) with the lattice parameters a = 849.76(3), c = 2099.8(2) pm, V = 1.3131(2) nm3, and six formula units per unit cell (Z = 6). It was synthesized at high-pressure/high-temperature conditions in a multianvil device. Single-crystal and powder X-ray diffraction experiments were conducted.

High-pressure synthesized perovskite-type CeTaN&lt;sub&gt;2&lt;/sub&gt;O and its magnetic and electrical properties

Recently, it has been discovered that the &lt;i&gt;AB&lt;/i&gt;(N,O)&lt;sub&gt;3&lt;/sub&gt;-type perovskite oxynitrides exhibit excellent dielectric, ferroelectric, and photocatalytic properties, promising for applications in the fields of optoelectronics, energy storage, and communication. Due to the differences in charge, ionic radius, and covalent bonding between N&lt;sup&gt;3–&lt;/sup&gt; ion and O&lt;sup&gt;2–&lt;/sup&gt; ion, the N substitution for O enhances the &lt;i&gt;B&lt;/i&gt;(N,O)&lt;sub&gt;6&lt;/sub&gt; octahedron tilting, giving rise to exotic properties and functionalities. However, the current fabrication process for this type of material is rather time-consuming, leading to products with an appreciable quantity of impurities. In this study, using oxide precursors and sodium amide as the nitrogen source, high-purity perovskite-type oxynitride CeTaN&lt;sub&gt;2&lt;/sub&gt;O bulk materials are successfully synthesized under high-temperature and high-pressure conditions provided by a cubic-anvil press. The synthesis time decreases to 1 h, achieving rapid production. The lattice structure and physical properties of the obtained samples are comprehensively investigated. X-ray powder diffraction experiments and subsequent Rietveld refinement indicate that the title material shows an orthorhombic crystal structure with the space group of &lt;i&gt;Pnma&lt;/i&gt;. The X-ray absorption spectra confirm the charge configuration and the anion composition as Ce&lt;sup&gt;3+&lt;/sup&gt;Ta&lt;sup&gt;5+&lt;/sup&gt;N&lt;sub&gt;2&lt;/sub&gt;O. Magnetization and specific heat measurements reveal that the exchange interactions are mainly antiferromagnetic, with a potential magnetic transition below 2 K. The electrical transport data demonstrate typical semiconductor behaviors, which can be further explained by a three-dimensional variable-range hopping model. Our study paves the way for putting this exotic perovskite oxynitride into practical applications.

Guest-selective shape-memory effect in a switchable metal-organic framework DUT-8(Zn).

Crystal size engineering allows tailoring of flexible metal-organic frameworks (MOFs) to achieve new properties. The gating type flexibility of the DUT-8(Zn) ([Zn2(2,6-ndc)2(dabco)]n, 2,6-ndc = 2,6-naphthalene dicarboxylate, dabco = 1,4-diazabicyclo-[2.2.2]-octane) compound is known to be extremely particle size sensitive. Here, the physisorption of ethanol vapor gives rise to so-called shape-memory effect, leading to rigidification and flexibility suppression. According to powder X-ray diffraction and nitrogen physisorption experiments, the open pore phase is retained selectively after desorption of alcohols, which could be attributed to the nano-structuring and surface deformation of the crystals as a result of exposure to alcohols.

In-situ X-ray diffraction study of Nb-doped Bi2Se3 crystal growth revealing unavoidable misfit layer compound

Temperature-resolved in-situ powder X-ray diffraction (PXRD) experiments were performed during synthesis of Nb-doped Bi2Se3 to gain important insights into the phase formation. The crystallization of phases upon heating the pure elements with the nominal composition of Nb0.25Bi2Se3, displays the formation of a misfit layer compound, (BiSe)1.1NbSe2, as a secondary phase. It was also discovered that a misfit-related intermediate phase appears right before Bi2Se3 melts and then misfit (BiSe)1.1NbSe2 crystallizes. This implies that to prevent the formation of the misfit phase, the synthesis temperature should remain well below the melting point of Bi2Se3. Powder samples of Nb-doped Bi2Se3, synthesized at 600 and 650∘C, aimed for this, however, they all displayed traces of the misfit phase. Additionally, multiple superconducting transitions were observed as non-quenched samples showed signs of NbSe2, which were removed by quenching the samples. This study has important implications for the synthesis and properties of Nb-doped Bi2Se3, towards the realization of topological superconductors.

Towards understanding the functional mechanism and synergistic effects of LiMn2O4 - LiNi0.5Mn0.3Co0.2O2 blended positive electrodes for Lithium-ion batteries

Blended positive electrodes consisting of mixtures of LiMn2O4 spinel (LMO) and layered LiNi0.5Mn0.3Co0.2O2 (NMC) have been studied by coupling electrochemical testing to operando synchrotron based X-ray absorption and powder diffraction experiments to shed light on their redox mechanism. Blending NMC with LMO results in enhanced energy density at high rates, with the composition with 25% LMO exhibiting the best electrochemical performance. Tests with a special electrochemical setup detecting the contribution of each blend component indicate that the effective current load on each blend component can be significantly different from the nominal rate and also varies as function of SoC. Operando studies enabled to monitor the evolution of oxidation state and changes in the crystal structure, which are in agreement with the expected behaviour of the individual components considering the material specific electrochemical current loads. These findings should contribute to a deeper mechanistic understanding of blended electrodes to foster a rational driven approach for their design.

A pH-Stable Tb-MOF as Luminescence Sensor for Highly Sensitive Detection of Amino Acids through Diverse Sensing Mechanism.

A luminescent Tb-MOF with excellent stability and dual-emitting properties was constructed with an amide-functionalized tetracarboxylate ligand. Tb-MOFs were initially assembled on one-dimensional Tb3+ chains, then formed a two-dimensional double-decker layer through the synergistic linking of organic ligands and bridging formic acid anions, and further fabricated the final three-dimensional structure through the connection of the organic ligands. Powder X-ray diffraction experiments revealed that Tb-MOFs not only exhibited excellent stability in water but also maintained structural integrity in the pH range of 2-12. Importantly, this Tb-MOF provided the first example of a metal-organic framework (MOF)-based luminescence sensor that can simultaneously detect two acid amino acids (aspartic and glutamic acids) through a turn-off sensing mechanism and two basic amino acids (lysine and arginine acids) through unusual turn-on and turn-off-on sensing mechanisms. Moreover, high sensitivity, low detection limit, and excellent recyclability of this sensor endow Tb-MOFs with great potential as a highly efficient amino acid fluorescence sensor in chemical detection and biological environments.

Crystal structure simulation of cationic cholesteric Liquid-Crystal polyesters. Non-Viral vectors

The crystal structure of six cationic cholesteric liquid crystal polyesters with choline, ammonium, and amide end groups are reported: PTOBEE-Choline [(C26H20O8)n-C5H13N]; PTOBDME-Choline [(C34H36O8)n-C5H13N]; PTOBEE-Ammonium [(C26H20O8)n-C5H13N]; PTOBDME-Ammonium [(C34H36O8)n-C5H13N]; PTOBEE-Amide (C26H19O9N)n and PTOBUME-Amide (C33H33O9N)n, have demonstrated non-viral vector properties in gene therapy by delivering DNA to the cell nucleus. They were synthesized by functionalization of precursor racemic polyesters via a condensation reaction between 4,4′-(terephthaloyl-di-oxydibenzoic chloride) (TOBC) and the racemic mixture of glycol (R-S-1,2-butanediol) or (R-S-1,2-dodecanediol), respectively. The resulting helical macromolecular structures exhibit unexpected optical activity and chiral morphology, previously attributed to the kinetic resolution of one preferable helical conformer of the possible four observed by NMR. Conformational analysis and energy minimization are performed on the four helical conformer monomeric models which are then polymerized to obtain helical chains. Three levels of chirality were observed in these polymer structures. Crystal models are built in triclinic primitive P1cells, with their molecular chains oriented parallel to the Z-axis (c lattice parameter equal to the helical pitch length), the cell parameters are obtained by performing geometry optimization tasks. A raw estimation of the relative weight of the four possible helical conformers on each synthetic cationic polymer has been performed on ideal mixtures considering their approximate known crystal structure with their experimental X-ray powder diffraction by Powder Quantitative Phase Analysis. The results would confirm the theory of the preferable recrystallization of a diastereoisomer, among the four possible, during the synthetic procedures. These findings shed light on the observed optical activity and provide insights into the crystal structure of these cationic polymers. The morphology of the cationic polymers is studied by ESEM in wet samples and crystals after drying the solvent.

Na6Li4MO4(CO3)4 (M = W and Mo): An Alternative Electrolyte for High-Temperature Electrochemical Cells.

Two new acentric oxycarbonates Na6Li4MO4(CO3)4 (M = W and Mo) were synthesized via a conventional solid-state route. Their structure was determined from X-ray diffraction data on single crystals. Na6Li4MO4(CO3)4 (M = W and Mo) crystallizes in the acentric cubic P-43m space group (a ≈ 7.15 Å). It is composed of MLi4O16 units built from MO4 and LiO4 tetrahedra and linked by CO32- groups to form a three-dimensional framework in which Na+ ions are inserted. We showed from differential scanning calorimetry and powder X-ray diffraction experiments that the melting is congruent (T ∼525 °C). In the solid and molten forms, conductivity was measured for both oxycarbonates by electrochemical impedance spectroscopy with three various gas compositions (CO2 100 vol %, CO2-air 70-30 vol %, and CO2-air 20-80 vol %). Each time, the stability of the electrical behavior was checked via heating and cooling cycles. The conductivity of both solid and molten phases is purely ionic and in the same order of magnitude as for the classical molten alkali electrolyte made of Li-Na or Li-K carbonates. As activation energies are also comparable, those new oxycarbonates appear to be promising electrolytes for electrochemical devices.