Synthesis, growth and characterization of bis (glycine) lithium molybdate—A semi-organic NLO material

Single crystals of bis (glycine) lithium molybdate [BGLM] with dimensions 20 mm × 10 mm × 5 mm were grown by slow evaporation technique. The grown crystals were subjected to powder X-ray diffraction studies. Functional groups of the crystallized molecules were confirmed by FTIR analyses. Transmission range of the crystal was determined by UV–vis–NIR spectra. Vickers microhardness test was performed on the prominent plane (0 1 1) of the grown crystal. The NLO property of the crystal was confirmed by Kurtz SHG test and compared with NLO efficiency of KDP crystal.     

Effect of crystallization temperature on the crystalline phase content and morphology of poly(vinylidene fluoride)

The effect of temperature on the crystallization of α, β, and γ phases of PVDF from dimethylacetamide (DMA) solution was studied. Variation in the crystallinity content of these three phases was obtained as a function of temperature using infrared spectroscopy, differential scanning calorimetry (DSC) and x-ray diffraction techniques. Such variation is related to the dependence of the crystallization rate of each phase with temperature, and allowed a better understanding of some results found in the literature about the crystallization and interconversion of these phases. Micrographs of samples present morphologies that corroborate with the proposed explanations. © 1994 John Wiley & Sons, Inc.     

Effect of deposition temperature on the growth mechanism of chemically prepared CZTGeS thin films

The Cu₂ZnSnGeS₄ (CZTGeS) thin films were deposited by the spray pyrolysis method at different substrate temperatures without further sulfurization. The influence of various deposition temperatures on the surface morphology, microstructure, optical properties, chemical, and phase composition were investigated. The substitution mechanism of Sn/Ge in the crystal lattice of CZTGeS depending on deposition temperatures was studied. It was shown that a variation in substrate temperature has a strong effect on the surface morphology of the films. The X-ray diffractometer (XRD), transmission electron microscope (TEM), and Raman spectroscopy (RS) analysis showed that CZTGeS films were polycrystalline with a kesterite-type single-phase structure and a preferential orientation of (112). The RS-mapping analysis showed the distribution of intensities on the surfaces of the films. Optical measurements showed that CZTGeS films are highly absorbing in the visible region, and the optical band gap is shifted from 1.89 to 1.84 eV.     

Structural,Hirshfeld surface and spectroscopic studies of the noncentrosymmetric 1-ethylpiperazinediium pentachloroantimonate (III) monohydrate

1-Ethylpiperazinediium pentachloroantimonate (III) monohydrate, C₆H₁₆N₂SbCl₅·H₂O, has been synthesized by the reaction of antimony trioxide (Sb₂O₃) and 1-ethylpiperazine in an aqueous solution of hydrochloric acid. The structure crystallizes in orthorhombic system, in the non-centrosymmetric space group Pca2₁ and consists of isolated [C₆H₁₆N₂]²⁺ cations, square pyramidal [SbCl₅]²⁻ anions and lattice water molecules. OH⋯Cl hydrogen bonds link the [SbCl₅]²⁻ anions and water molecules to form double chains stretching along the [101] direction. The chains in turn are linked to the organic cations via NH⋯Cl, CH⋯Cl, CH⋯O and NH⋯O hydrogen bonds to form a three-dimensional network. This structure presents an example of a general square pyramidal complex ion containing a stereo-chemically active lone pair of electrons. Solid state ¹³C and ¹⁵N CP-MAS NMR spectra are in agreement with the X-ray structure, and vibrational absorption bands were identified by infrared spectroscopy. DFT calculations allowed the attribution of the NMR peaks and IR absorption bands. The interactions variability of the two independent cations and ten chloride atoms is analyzed via Hirshfeld surface analysis.     

Photochemical reaction of W(CO)6 with SnCl4 II. Synthesis and X-ray structure of tetrachlorobis(triphenylphosphine oxide)tungsten(IV), [WCl4(OPPh3)2]

The crystal structure of [WCl₄(OPPh₃)₂](1), formed in the photochemical reaction of W(CO)₆ with SnCl₄ in the presence of triphenylphosphine, has been determined by the single-crystal X-ray diffraction method. The compound crystallizes in the monoclinic space C2/c, with A=14.027(3), B=13.163(3), C=19.621(4) Å, β=96.36(3)°, Z=4. The structure solved by heavy-atom methods has been refined to R=0.0466, for 3489 observed reflections.

The [WCl₄(OPPh₃)₂] molecule possesses a crystallographically imposed C₂ axis passing through the tungsten atom. Despite steric demands, a mutually cis arrangement of triphenylphosphine oxide oxygens is found for [WCl₄(OPPh₃)₂], while there is a slight lengthening of the W---Cl bonds trans to the oxygen atoms.     

Influence of organic solvent on tristhioureazinc(II)sulphate crystals

It was observed that the addition of a very small quantity (5·10⁻³ M L⁻¹) of an organic solvent, benzene (C₆H₆) in the aqueous growth medium (pH ∼5.9) of tristhioureazinc(II)sulphate (ZTS) markedly influences the SHG efficiency. The measurements using Nd:YAG laser source reveal that second harmonic generation (SHG) conversion efficiency which is one of the most important nonlinear optical (NLO) properties is enhanced by benzene dopant by a factor of nearly 1.5 times. The crystalline perfection of the grown crystals was evaluated by high-resolution X-ray diffractometry (HRXRD). The full width at half maximum (FWHM) of the diffraction curve (which gives an estimate for the degree of crystalline perfection) for undoped and benzene doped specimen crystals are 26 and 15 arc sec, respectively. The reduction in FWHM due to the benzene solvent indicates the significant improvement in crystalline perfection. This very much suggests that the dissolution of trace impurities in the presence of benzene prevents the entry of impurities into the crystal lattice and at the same time enhances the growth promoting effect (GPE). Not much variation is observed in XRD, FTIR and TG-DTA of ZTS in the presence and absence of benzene in the aqueous growth medium.     

ChemInform Abstract: Gas-Phase Electron-Diffraction Studies of the Molecular Structures of Tetrabromo(sulfido)tungsten(VI), WSBr4, and Tetrabromo(seleno)tungsten( VI), WSeBr4.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Structural investigation and Hirshfeld surface analysis of two polymorphs of 2-(4-Methylbenzamido)-5-(4-fluoro-3-phenoxyphenyl)-1,3,4-thiadiazoles

In this report, the crystal structure of a new polymorphic form of 2-(4-Methylbenzamido)-5-(4-fluoro-3-phenoxyphenyl)-1,3,4-thiadiazole have been investigated and compared with the previously reported form. Crystallization experiments from a non-polar solvent resulted in the formation of a newly obtained polymorph of this substituted 1,3,4 thiadiazole compound. Structural differences and similarities in both the polymorphic forms were explored in terms of supramolecular building blocks present in the crystal packing and their influences on the supramolecular construct are investigated in terms of the nature and energetics of the associated interactions. In addition, Hirshfeld surface analysis and calculations on the enrichment ratio were carried out for both the forms to isolate the various types of interatomic contacts and differentiate their contribution towards the molecular assembly, as obtained from 2D fingerprint plots. Also, the interaction energies were computed for the new polymorph and compared with the reported form. The studies render quantitative insights into the role of strong H-bonds and weak intermolecular interactions acting cooperatively in the crystal. In addition, the role of both electrostatic and dispersion energies contributes to the overall stability in the crystal packing.     

Morphology and crystallinity of the two diastereomer racemates of triglycidyl isocyanurate (TGIC)

Triglycidyl isocyanurate [2451-62-9] is a trifunctional monomer containing epoxy groups, and is presently used mainly for cross-linking carboxyl-functional polyester resins in powder coatings. There are three chiral carbon atoms in its molecule, and due to its symmetrical structure four antipodes exist according to the configuration of the chiral carbon atoms; namely RRR, SSS, RRS and SSR. Therefore the synthesized or commercially available TGIC is a physical mixture of two diastereomer racemates, i.e. beta-TGIC or RRR/SSS and alpha-TGIC or RRS/SSR. The physical and chemical properties of the two diastereomer racemates of TGIC are different. Their morphology and crystalline structure have been determined by polarizing microscopy and X-ray diffraction analysis. Beta-TGIC has hexagonal symmetry and belongs to the space group R3 or R3m. The cell parameters are: a₀ = 14.037 Å, c₀ = 11.55 Å, and cell volume: V₀ = 1970.88 Å³. Alpha-TGIC has orthorhombic crystallinity and belongs to the space group Pna2₁. Its cell parameters are: a₀ = 9.29 Å, b₀ = 9.48 Å, c₀ = 15.66 Å and cell volume: V₀ = 1379.16 Å³.     

Crystal structures and chemistry of double perovskites Ba2M(II)M′(VI)O6 (M=Ca, Sr, M′=Te, W, U)

Structures of the double perovskites Ba₂M(II)M ′(VI)O₆ (M=Ca, Sr, M′=Te, W, U) at room temperature have been investigated by the Rietveld method using X-ray and neutron powder diffraction data. For double perovskites with M=Sr, the observed space groups are I2/m (M′ =W) and (M′=Te), respectively. In the case of M=Ca, the space groups are either monoclinic P2₁/n (M′=U) or cubic (M′=W and Te). The tetragonal and orthorhombic symmetry reported earlier for Ba₂SrTeO₆ and Ba₂CaUO₆, respectively, were not observed. In addition, non-ambient X-ray diffraction data were collected and analyzed for Ba₂SrWO₆ and Ba₂CaWO₆ in the temperature range between 80 and 723 K. It was found that the rhombohedral structure exists in Ba₂SrWO₆ above room temperature between the monoclinic and the cubic structure, whereas the cubic Ba₂CaWO₆ undergoes a structural phase transition at low temperature to the tetragonal I4/m structure.     

Effect of nonsolvent additive on the surface morphology and the gas separation performance of poly(2,6-dimethyl-1,4-phenylene)oxide membranes

Integrally skinned asymmetric membranes were prepared from poly(2,6-dimethyl-1,4-phenylene)oxide (PPO) using different nonsolvent additives. These nonsolvent additives consisted of branched and linear alcohols ranging from C₃ to C₁₀. Permeation data of these membranes were obtained from a constant pressure permeation system for pure gases of CO₂, CH₄, O₂ and N₂. An empirical correlation relating the pure gas permeance ratio of CO₂/CH₄ and the structural components of the nonsolvent additives has been proposed. The membranes were characterized by atomic force microscope (AFM) and intrinsic viscosity measurements. It was observed that there were two types of surface morphologies: merged nodules and discrete nodules. The appearance of the nodules were reflected in the mean roughness data, R_a. It was revealed that membranes with smaller and merged nodules resulted in higher pure gas permeance ratios for O₂/N₂ and CO₂/CH₄ with the exception of 3,5,5-trimethyl-1-hexanol and 3-ethyl-2,2-dimethyl-3-pentanol. The microscopic studies showed that the membranes containing discrete nodules resulted in lower pure gas permeance ratios for O₂/N₂ and CO₂/CH₄. It was observed that nonsolvent additives that possess a long straight hydrocarbon chain such as 2-ethyl-1-hexanol, 1-octanol and 2-decanol produced the highest pure gas permeance ratios.     

New insight into the symmetry and the structure of the double perovskites Ba2LnNbO6 (Ln=lanthanides and Y)

Structures of the double perovskites Ba₂LnNbO₆ (Ln=La, Pr, Nd, Sm, Eu, Tb, Dy, Ho, and Y) at room temperature have been re-examined by Rietveld profile analysis of X-ray diffraction data. It was shown that the correct phase sequence across the lanthanides is I2/m (Ln=La, Pr, Nd, and Sm), I4/m (Ln=Eu, Gd, Tb, and Dy), and (Ln=Ho and Y), respectively. All phases can be derived from the ideal cubic perovskite by ordering the Ln(III) and Nb(V) ions and by out-of-phase tilting the LnO₆/NbO₆ octahedra around either the primitive two-fold [110]_p-axis (I2/m) or the four-fold [001]_p-axis (I4/m). The monoclinic P2₁/n structure that contains both out-of-phase and in-phase tilt around the primitive [110]_p- and [001]_p-axis, respectively, has not been observed for this series of compounds.     

Magnetic field effects on the crystal orientation and surface morphology of electrodeposited iron films

The effects of a magnetic field (5 T) on crystal orientation and surface morphology were investigated for iron films electrodeposited in ferrous aqueous solution. XRD measurements for the iron films showed that the preferred orientation parallel to the substrate was determined by the current density and not influenced by the magnetic field. By X-ray pole figure measurements, however, the crystal texture of the iron films electrodeposited at 10 mA cm^–2 and 30 mA cm^–2 was found to be controlled by the magnetic field. That is, the (110) planes were orientated in same direction of the magnetic field vector at angles of 30° and 35° to the direction normal to the substrate plane at 10 mA cm^–2 and 30 mA cm^–2, respectively. When the morphology was observed by SEM, iron grains at 30 mA cm^–2 changed from a triangular pyramid shape at 0 T to a complex star-like shape at 5 T.Presented at the 3rd International Symposium on Electrochemical Processing of Tailored Materials held at the 53rd Annual Meeting of the International Society of Electrochemistry, 15–20 September 2002, Düsseldorf, Germany     

不同制备工艺聚硅氯化铝的红外光谱和晶貌研究

聚硅金属盐 (主要是铝盐和铁盐 )是一类新型高效无机高分子混凝剂 ,不同的制备工艺会获得分子相对质量不同 ,分子结构有差异 ,因而混凝效果与稳定性能明显不同的产品。由于基础研究过于薄弱 ,严重影响了其实行大规模工业生产[1] 。聚硅氯化铝 (ＰＡＳＣ)属于聚硅金属盐 ,它的制备大多采用将聚硅酸与铝盐混合 ,在陈化中令其自然聚合 (或适当加热 )的方法[2～ 4 ] 。作者在该方法的基础上增加碱化聚合手段 ,继而引入代号为Ａ的聚合助剂 ,使制得的ＰＡＳＣ具有更好的混凝效果[5] 。为此 ,对不同制备工艺的ＰＡＳＣ进行红外光谱和晶形貌象研究 ,…     

Determination of equilibrium humidities using temperature and humidity controlled X-ray diffraction (RH-XRD)

Confined growth of crystals in porous building materials is generally considered to be a major cause of damage. We report on the use of X-ray diffraction under controlled conditions of temperature and relative humidity (RH-XRD) for the investigation of potentially deleterious phase transition reactions. An improved procedure based on rate measurements is used for the accurate and reproducible determination of equilibrium humidities of deliquescence and hydration reactions. The deliquescence humidities of NaCl (75.4 ± 0.5% RH) and Ca(NO₃)₂·4H₂O (50.8 ± 0.7% RH) at 25 °C determined with this improved RH-XRD technique are in excellent agreement with available literature data. Measurement of the hydration of anhydrous Ca(NO₃)₂ to form Ca(NO₃)₂·2H₂O revealed an equilibrium humidity of 10.2 ± 0.3%, which is also in reasonable agreement with available data. In conclusion, dynamic X-ray diffraction measurements are an appropriate method for the accurate and precise determination of equilibrium humidities with a number of interesting future applications.     

Studies on the growth, optical, electrical and spectral properties of potassium pentaborate (KB5) single crystals

The bulk single crystals of nonlinear optical material potassium pentaborate (KB5) have been grown by slow evaporation solution growth technique using water as solvent. The grown crystal was confirmed by single crystal X-ray diffraction studies. The structural perfection of the grown crystals has been analyzed by high resolution X-ray diffraction (HRXRD) studies by recording rocking curve. The photoluminescence (PL), UV-vis spectral studies were performed and the optical bandgap of the material was calculated. FTIR and FT-Raman measurements enumerate the functional groups present in the compound. The factor group analysis on KB5 reveals that there are 117 vibrational optical modes. The dielectric behavior of KB5 was investigated with different frequencies and temperatures.     

Spectroscopic investigations on the photodegradation of toluidine blue dye using cadmium sulphide nanoparticles prepared by a novel method

A novel method to prepare cadmium sulphide nanoparticles (CdS NPs) possessing nearly uniform size was adopted using eggshell membrane (ESM), under different pH conditions. Significant yield of CdS NPs with smallest possible size was obtained by increasing the pH of the reaction medium from acidic to alkaline. The above prepared CdS NPs have been characterized by UV-vis absorption as well as emission spectra, powder X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The efficiency of the above prepared CdS NPs as a catalyst for the photodegradation of toluidine blue (TB) dye, as a function of pH as well as the ratio between the catalyst and the substrate was studied after irradiation with UV light. The results showed that an efficient interaction took place between the catalyst and the substrate to cause degradation of the selected dye. A maximum degradation of toluidine blue dye (90%) was observed at pH 8 which is higher than that of the efficiencies at pH 4 and pH 6.     

X-ray and neutron powder diffraction study of the double perovskites Ba2LnSbO6 (Ln=La, Pr, Nd and Sm)

The crystal structures of Ba₂LnSbO₆ (Ln=La, Pr, Nd and Sm) at room temperature have been investigated by profile analysis of the Rietveld method using either combined X-ray and neutron powder diffraction data or X-ray powder diffraction data. It has been shown that the structure of Ba₂LnSbO₆ with Ln =La, Pr and Nd are neither monoclinic nor cubic as were previously reported. They are rhombohedral with the space group . The distortion from cubic symmetry is due to the rotation of the LnO₆/SbO₆ octahedra about the primitive cubic [111]_p-axis. On the other hand, the structure of Ba₂SmSbO₆ is found to be cubic. All compounds contain an ordered arrangement of LnO₆ and SbO₆ octahedra.     

On the crystal structures of Ln3MO7 (Ln=Nd, Sm, Y and M=Sb, Ta)—Rietveld refinement using X-ray powder diffraction data

We have investigated, using X-ray powder diffraction data, the crystal structures of some fluorite derivatives with the formula Ln₃MO₇ (Ln=lanthanide or Y and M=Sb and Ta). In these compounds ordering of Ln and M occurs, leading to a parent structure in Cmmm. Tilting of the MO₆ octahedra causes doubling of one of the cubic axes, leading to a number of non-isomorphic subgroups, e.g. Cmcm, Ccmm and Cccm. We have identified an alternative space group Ccmm instead of C222₁ for those compounds containing a medium sized lanthanide or Y and M being Sb or Ta. Interestingly this is an alternative setting for the space group of the structure obtained when Ln is large (Cmcm). However, there tilting of the octahedra is around the a-axis of the parent structure, rather than around the b-axis as it is found in the compounds which we are reporting on here.In one compound, Nd₃TaO₇, both tilts occur. The phase transition between the two possible structures is a slow and difficult process above 80 K, allowing both phases to coexist.     

Structural analysis of several W(VI) and Mo(VI) complex perovskites prepared by the polymeric precursors method

We describe in this work the synthesis by the Pechini method of five Mo(VI)- and W(VI)-containing complex perovskites and their structural characterisation by HREM and XRD. The compounds studied, Ba(B_2/3′B_1/3″)O₃ (B′=In and Y; B″=W and Mo) and Sr(In_2/3W_1/3)O₃, were obtained after firing the precursor powders for 8 h at 1200°C. Thermal analysis showed that the formation mechanism of the five perovskites is similar and implies the formation of barium carbonate and barium tungstates or molybdates of different stoichiometries as intermediate phases. Interesting enough, these similar mechanisms yield to materials of a quite different structure. Indeed, Ba(In_2/3Mo_1/3)O₃ and Sr(In_2/3W_1/3)O₃ were found to be disordered perovskites (unit cells: a_p×a_p×a_p and , respectively); on the other hand, two phases coexist in the sample Ba(In_2/3W_1/3)O₃ at the synthesis conditions: an ordered predominant phase (unit cell: 2a_p×2a_p×2a_p) and, as a minor phase, a disordered perovskite (unit cell: a_p×a_p×a_p). Finally, the two yttrium-containing compounds were found to be ordered perovskites (2a_p×2a_p×2a_p).