Growth and characterisation of gadolinium samarium oxalate single crystals

Single crystals of Gadolinium Samarium Oxalate (GSO) are grown by gel method. The crystals are pale yellowish in colour. Morphology and size of the crystals are found to depend on pH of the medium, gel density, concentration of the reactants and acidity of the feed solution. The crystallinity of the grown sample was confirmed by X‐ray diffraction studies and the lattice parameters were determined. X‐ray diffractogram shows well defined peaks. IR spectrum confirms the presence of water molecules and carboxylic group. EDAX analysis confirms the presence of Gd and Sm in the sample. The thermal decomposition behaviour of the crystal was analysed using TGA and DTA studies. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structure and magnetism of manganese‐doped ZnO powder samples

The magnetic and structural properties of manganese‐doped ZnO powder samples prepared by a solid state method are reported. Magnetization measurements indicate ferromagnetic behavior, with hysteresis observed in the M vs. H behavior at 300 K. Coercive fields were <100 Oe at 300 K. Temperature‐dependent magnetization measurements showed evidence for ordering temperatures of >300 K. However, the results show that ferromagnetism originates from the doped matrix rather than any type of magnetic cluster and the ferromagnetism is due to the defects and/or oxygen vacancies confined to the surface of the grains. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structures and spectroscopic characterization of chiral and racemic 4‐phenyl‐1,3‐oxazolidin‐2‐one

Crystal structures of (R)‐ and (rac)‐4‐phenyl‐1,3‐oxazolidin‐2‐one (4‐POO) have been determined by X‐ray diffraction and characterized by the solid state ¹³C NMR and IR spectra. Molecular geometries and intermolecular interactions in (R)‐ and (rac)‐4‐POO crystals are very similar to each other; 4‐POO molecules are linked via the N‐H…O intermolecular hydrogen bonds to form the chained structure. Chemical shifts of the solid state ¹³C NMR spectra are very similar to each other, whereas the ¹H spin‐lattice relaxation times (T_1H) value for (R)‐4‐POO is five times as large as that for (rac)‐4‐POO, reflecting the more restricted mobility of the (R)‐4‐POO chain. Although both crystals contain an unique molecule in the asymmetric unit, a doublet feature is observed for the C=O stretching mode in the IR spectra of (R)‐ and (rac)‐4‐POO crystals. The frequency gap of the C=O bands are correlated with the strength of the dipole‐dipole interactions between the neighboring C=O groups. © 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

The combined effects of supersaturation and Ba2+ on the batch cooling crystallization of potassium dihydrogen phosphate

The combined effects of supersaturation and Ba²⁺ on potassium dihydrogen phosphate (KDP) were investigated in batch cooling suspension crystallization. Growth size, morphology, and impurity Ba²⁺ adsorbed in the KDP crystals were measured with changing Ba²⁺ concentration and supersaturation. Significant changes in shapes and volume of the grown crystals have been observed. The results further confirmed that the size and shape of crystals were greatly determined by supersaturation. Ba²⁺ ions significantly modified the growth habit of KDP crystals. The concentration of Ba²⁺ ions adsorbed in the crystals increases with the increasing Ba²⁺ ions in the solutions and supersaturation. The foggy phenomena caused by the addition of Ba to the KDP solution were also described. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Single crystal growth of CaMg2(SO4)3 via solid‐ / gas‐phase reactions and its Nasicon‐related crystal structure

Crystals of the double sulfate CaMg₂(SO₄)₃ have been obtained by solid‐state reactions of stoichiometric amounts of anhydrous CaSO₄ and MgSO₄ in sealed and evacuated silica tubes with chlorine gas as mineraliser. The crystal structure was determined from single crystal X‐ray diffractometer data [P 6₃/m, Z = 2, a = 8.3072(4), c = 7.3057(8) Å, R [F² > 2σ (F²)] = 0.0317, wR (F² all) = 0.0785, 476 structure factors, 33 variable parameters] and consists of distorted [CaO₆] octahedra (3 symmetry), [MgO₆] octahedra (3 symmetry) and SO₄ tetrahedra (m symmetry) as single building units. The structure is made up of ¹_∞[CaO_6/2] chains of face‐sharing [CaO₆] octahedra that extend parallel to [001], alternating with columns of face‐sharing [MgO_3/1O_3/2]₂ dimers. Both types of chains are linked via corner‐sharing with SO₄ tetrahedra into a three‐dimensional framework structure. Although the compound crystallizes in a new structure type, it is topologically related to the NaZr₂(PO₄)₃ (Nasicon) structure, and a comparative discussion between both structural arrangements is given. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of SiO32‐ impurity on growth habit of potassium dihydrogen phosphate crystal

By altering the concentration of silicate (SiO₃^2‐) impurity in the solution, a series of potassium dihydrogen phosphate (KDP) crystals was obtained by the conventional temperature cooling and the rapid growth methods, respectively. It was observed that the presence of SiO₃^2‐ made KDP crystals tapering in conventional cooling method, while more SiO₃^2‐ induced inclusions at prismatic sectors in the rapid growth method. Laser‐polarization‐interference results showed that SiO₃^2‐ extended the dead zone and reduced the growth rate of (100) face of KDP crystals. The negative influence of SiO₃^2‐on the growth was considered absolutely similar to the effect of cations. It was also suggested that the stability of solution doped with SiO₃^2‐ was improved without seed crystals, while it was destructed with seed crystals. The inhibition mechanism was analyzed in terms of SiO₃^2‐ absorption on (100) face. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth of dl-malic acid-doped ammonium dihydrogen phosphate crystal and its characterization

Single crystals of dl-malic acid-doped ammonium dihydrogen phosphate have been grown using slow evaporation method and also by Sankaranarayanan–Ramasamy (SR) method with the vision to improve the properties of the ADP crystals. The characterization of grown crystals was made by single-crystal X-ray diffraction, powder X-ray diffraction, UV–vis. spectroscopy, Fourier transform infrared spectroscopy (FTIR), differential thermal analysis (DTA), Vicker's microhardness, dielectric measurements, high-resolution X-ray diffraction (HRXRD) and second-harmonic studies. Structural difference between pure and doped crystal has been studied by XRD analysis. Functional groups were identified by FTIR spectroscopy. The grown crystals were found to be transparent in the entire visible region. Decomposition temperatures of the grown crystals were measured by DTA. Vicker's hardness study carried out on (0 0 1) face at room temperature shows increased hardness of the doped crystals and SR-method-grown crystals. Dielectric measurements reveal that SR-method-grown DLM-doped ADP crystals have low dielectric loss. Crystalline perfection of the grown crystals is analyzed using HRXRD. Preliminary measurements indicate that the second harmonic generation efficiency of the doped crystals at a fundamental wavelength of 1064 nm is roughly 1.5 times greater than that of pure ADP.     

XRD,IR, and Raman investigations of structural properties of Dy2‐xHox O3 prepared by sol gel procedure

The Rare earth mixed oxides Dy_2‐xHo_x O₃ (0.0 ≤ x ≤ 2.0) solid solution was synthesized by a sol–gel process. X‐ray diffraction (XRD) data were collected and crystal structure and microstructure analyses were performed applying Rietveld refinement method. Infrared and Raman spectroscopy were used to define the microstructure and to locally probe the structure of the samples. The cationic distribution over the two non‐equivalent sites 8b and 24d of the space group Ia3 is found to be randomly. The crystallite size and microstrain as well as Raman modes positions are influenced by Ho³⁺ concentration. The apparent size is isotropic but significant anisotropy is found for the microstrain with its largest value along the crystallographic direction [h00]. Inspite the single phase solid solution confirmed by Rietveld analysis for all samples, Raman spectra detected the coexistence of two phases; cubic and distorted monoclinic of too small amount or highly disordered, i.e. amorphous like, to be detected by XRD. The result indicates the ability of Raman spectroscopy to detect minor phases in solid solutions. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis of nanoflakes‐based self‐assembling crossed structure of stannous oxide and photocatalysis property

Self‐assembling nanoflakes‐based crossed architectures of stannous oxide (SnO) were successfully synthesized via template‐free hydrothermal growth method by using SnCl₂·2H₂O and KOH as precursors. Crystal structures, morphology, chemical composition and optical properties were examined by X‐ray diffraction (XRD), field‐emission scanning electron microscopy (FESEM), energy dispersive X‐ray analysis, and Raman spectroscopy, respectively. The results indicate that the as‐synthesized product belongs to tetragonal phase SnO with crossed morphology self‐assembled by nanoflakes. Furthermore, UV‐vis spectrophotometry was used to determine optical band gap of the SnO nanostructures and the direct band gap of 2.90 eV was obtained. The photocatalysis of the product has been evaluated with methyl orange and the high degradation ratio of 87% is obtained in 240 minutes under the measuring condition which is attributed to the wide band gap and large specific surface area of the nanoflakes‐based crossed SnO architectures. A possible growth mechanism is proposed in the end.     

Synthesis of superconducting sphere‐like Mo2C nanoparticles in an autoclave

Sphere‐like Mo₂C nanoparticles have been synthesized through the reaction of sodium molybdate, anhydrous ethanol and sodium azide at 450 °C for 10 h in a sealed stainless steel autoclave. X‐ray powder diffraction results indicated that the final product was Mo₂C. Transmission electron microscopy (TEM) and scanning elctron microscopy (SEM) were employed to characterize the as‐prepared sample. The sample was mostly composed of sphere‐like particles, which has a superconducting transition temperature of 9.5 K, and its calculated surface area is 30.859 m²/g. The experimental parameters such as reaction temperature and reactants were studied to investigate the reaction mechanism. It was found that sodium azide and reaction temperature played key roles in the formation of sphere‐like Mo₂C nanoparticles. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

X‐Ray Powder Diffraction,DTA and Vibrational Studies of CdNH4PO4.6H2O Crystals

Cadmium Ammonium Phosphate Hexahydrate (CAPH) is analogous to naturally occurring struvite. CAPH crystals are grown by slow evaporation technique. These crystals are characterised by X‐ray, TG‐DTA and Infra‐red studies. Powder X‐ray pattern indicates the orthorhombic crystal structure analogous to struvite. TG‐DTA analysis suggests loss of water of hydration (6H₂O) between 113 and 391°C. Later the substance melts and only Cd remains around 780 °C. Infra Red spectrum is characteristic of H₂O, PO₄^3‐ and NH₄⁺ radicals.     

Growth of barium oxalate crystals in agar–agar gel and their characterization

Single crystals of barium oxalate have been grown by gel method using agar‐agar gel as media of growth at ambient temperature. The optimum conditions were established by varying various parameters such as concentration of gel, concentration of reactant, gel setting time etc. Prismatic platy shaped transparent crystals were obtained. The grown crystals were characterized through powder X‐ray diffraction (XRD), Fourier transform infrared (FT‐IR) studies, Thermogravimetric (TGA) and Differential thermal analysis (DTA). The compound crystallizes under monoclinic structure with lattice parameters a = 6.6562 Å, b = 8.0464 Å, c = 2.8090 Å, β= 96.832°, and V = 149.38 ų. The FT‐IR spectrum indicates OH and carbonyl group along with the presence of metal‐oxygen bond. The TGA indicates 17.75% weight loss at 550°C from which the decomposition pattern is formulated. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and tribological properties of Mo‐doped WSe2 Nanolamellars

The Mo‐doped WSe₂ nanolamellars have been successfully prepared via solid‐state thermal (750 °C) reaction between micro‐sized W, Mo with Se powders under inert atmosphere in a closed reactor and characterized by X‐ray diffractometer (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that the morphologies of the as‐prepared products changed from microplates to nanolamellars to aggregations composed of nanoparticles with the doping of Mo powders. And the sizes of crystallites evidently reduced while the contents of dopant increased within a certain limit (1 wt.%–7 wt.%). The tribological properties of the as‐prepared products as additives in HVI750 base oil were investigated by UMT‐2 multispecimen tribotester. The friction coefficient of the base oil containing Mo‐doped WSe₂ nanolamellars was lower and more stable than that of WSe₂ nanolamellars. A combination of rolling friction, sliding friction, and stable tribofilm on the rubbing surface could further explain the good friction and wear properties of Mo‐WSe₂ nanoparticles as additives than that of WSe₂.     

Structural properties of bulk GaN substrates: Impact of structural anisotropy on non‐polar and semi‐polar crystals

In this paper we show the structural parameters and structural anisotropy of the bulk GaN substrates of various crystallographic orientations (00.1), (10.0), (11.0) and (20.1) obtained by ammonothermal method. The structural parameters were investigated using high resolution X‐Ray Diffraction. Perfect crystalline structure manifests in very narrow peaks in X‐ray rocking curves. The full width at half maximum (FWHM) values of 16 and 18 arcsec for the symmetrical and asymmetrical peaks, respectively, have been observed. In addition, we observed structural anisotropy in the non‐polar and semi‐polar crystals, depending on the orientation of the sample relative to the X‐ray beam. It is conducted that this anisotropy is a intrinsic property of non‐polar and semi‐polar GaN substrates.     

Spectroscopic properties of Zn‐naphtholimines‐TCNQ charge transfer complexes with variable ligand radicals

Over the last decades, many different types of charge transfer complexes have been discussed as organic metals. The design and synthesis of the required efficient p‐electron donors constitutes an active area of modern materials chemistry. An important family with these properties is based on naphtholimines, which are known to form electrically conductive salts with a variety of organic acceptor molecules such as tetracyano‐pquinodimethane (TCNQ). Since the reduction potential of transition metal complexes can be readily modified by the selection of proper ligands and ligand substitution, such complexes are favored candidates for designed syntheses. The present work is aimed toward the study of Zn‐Naphtholimines‐TCNQ charge transfer complexes with fractional electron transfer per formula unit. The electron transfer is an essential factor in the control of electrical conductivity. Of particular interest was the effect of ligand volume variations on the degree of charge transfer. Both IR‐ spectroscopy and electron paramagnetic resonance (EPR) spectroscopy were used as analytic tools. We found, that Zn[RNAFIN]₂‐2TCNQ molecules are partially ionized, and that the electron delocalization is strongly affected by the chosen ligand volume.     

Structural and magnetic studies of Mn‐doped ZnO

The bulk samples of Mn‐doped ZnO were synthesized with the nominal compositions Zn_1‐xMn_xO (x = 0.02, 0.05, 0.10, 0.15) by the solid‐state reaction and sol‐gel methods. In both the methods the samples were finally sintered at ∼700 °C in air. The X‐ray diffraction (XRD) studies of the samples synthesized by the solid‐state reaction method exhibit the presence of wurtzite (hexagonal) crystal structure similar to the parent compound (ZnO) in all the samples, suggesting that doped Mn ions sit at the regular Zn sites. However, same studies spread over the samples with Mn content ≥5% and synthesized by the sol‐gel method reveal the occurrence of some secondary phase in addition to the majority wurtzite phase. The magnetic measurements by vibrating sample magnetometer (VSM) clearly indicate ferromagnetic interaction at room temperature in all the samples. The Curie temperatures (T_c) and magnetization vary with concentration of Mn ions in the samples. However, the samples synthesized by sol‐gel method were found to have lower Tc values and also lower magnetization as compared to the corresponding samples synthesized by solid‐state reaction method. It could possibly be due to the presence of antiferromagnetic islands and smaller crystallite sizes in the samples prepared by sol‐gel method. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Vibrational, EPR and optical spectroscopy of the Cu doped glasses with (90-x)TeO2-10GeO2-xWO3 (7.5 ≤ x ≤ 30) composition

Infrared, EPR and optical absorption studies on (90-x)TeO₂-10GeO₂-xWO₃ (7.5 ≤ x ≤ 30) glasses containing Cu²⁺ spin probe have been carried out. The Infrared spectral studies show that the structure of glass network consists of [TeO₄], [TeO₃]/[TeO_3 + 1], [WO₄], [WO₆] and [GeO₆] units in the disordered manner. Physical parameters such as density (ρ), molar volume (V_m), oxygen packing density (OPD), oxygen molar volume (V_o), optical basicity (Λ), oxide ion polarizability (α_O²⁻), inter ionic distances and the concentration of ions per unit volume of Te, Ge, W, Cu and O have been determined. The spin-Hamiltonian parameters (g_||, g_⊥ and A_||) of Cu²⁺ ions in the present glasses have been estimated from EPR spectra at 300 K. Bonding parameters such as α², β₁², β², Γ_σ, and Γ_π have been calculated from both optical absorption and EPR data. The observed variations in spin-Hamiltonian parameters and bonding parameters have been correlated to the structural modifications due to the WO₃ incorporation into the TeO₂ glass network at constant 10 mol% GeO₂ content.     

Crystal growth,dielectric and FIR reflectivity studies on PZN(0.91)‐PT(0.09) single crystals

Crystal growth of PZN‐PT single crystals using slow cooling flux technique with PbO flux is reported in this communication. Optimum growth conditions to maximize the amount of perovskite are also suggested. The grown crystals are characterized by dielectric and FIR spectroscopy. Temperature dependence of ε′ very close to the transition temperature shows a first order phase transition. Diffused phase transition and strong frequency dependence of ε′ around transition temperature are also observed. The real part of ε′ was found to obey the relation ε′ – ε_∞ = χ′(T‐T_o)². Dispersion in the ferroelectric phase is suggested to originate from ordering of domains. Competition in the B‐site occupancy by Zn, Nb and Ti ions is suggested to be the origin for the additional modes in the FIR reflectivity at room temperature. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and characterization of L‐phenylalanine

L‐Phenylalanine (C₉H₁₁NO₂), having the morphology of spherulitic needles, an amino acid constituent, responsible for brain nutrition is crystallized in silica gel of pH 6.0 by single diffusion method in a period of 30 minutes. The grown crystals were characterized by X‐ray powder diffraction, Fourier Transform infrared spectroscopy and Visible Ultraviolet spectroscopy. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)