Growth,characterization and dielectric property studies of gel grown barium succinate single crystals

. Single crystals of barium succinate (BaC4H4O4) were grown in silica gel medium using controlled chemical reaction method. Plate-like single crystals of size up to 3 × 2 × 0·2 mm³ was obtained. Single crystal X-ray diffraction (XRD) studies confirmed that structure of the title compound is tetragonal. Powder X-ray diffraction (PXRD) pattern of the grown crystal and the Fourier transform infrared (FT–IR) spectrum in the range 400–4000 cm^–1 are recorded. The vibrational bands corresponding to different functional groups are assigned. Thermal stability of the grown crystals is confirmed by differential scanning calorimetry (DSC). Dielectric constant and dielectric loss have been calculated and discussed as a function of frequency at different temperatures.     

Growth and Solvent Effects of a Promising Nonlinear Optical Sodium Paranitrophenolate Dihydrate (NO2-C6H4-ONa∙2H2O) Single Crystal

Sodium paranitrophenolate dihydrate (NPNa∙2H2O) is an excellent semiorganic nonlinear optical (NLO) material, crystallizes both in water and methanol with high degree of transparency. Good optical quality single crystals of dimension upto 18 mm×6 mm×3 mm are obtained by sothermal solvent evaporation technique. The solubility of the crystal in different solvents was measured gravimetrically. The single crystals of NPNa∙2H2O show variation in physical properties and growth rate in different solvents. Methanol or ethanol solution yields crystals of bipyramidal shape with clear morphology. However, methanol grown crystal is exhibiting improved hardness parameters and possesses excellent thermal stability as compared to water grown crystals. The effects of solvent on hardness parameter along with thermal and optical properties of NPNa∙2H2O was revealed in this paper.     

Thermal and spectroscopic studies of as-grown l-arginine hydrochloride monohydrate crystals

Single crystals of l-arginine hydrochloride monohydrate (LAHCl) were successfully grown at ambient temperature (28.5°C) from its aqueous solution (pH=5.4) by slow evaporation as well as by slow cooling methods.The as-grown crystal is of dimensions 2.8×4.5×1.2 cm³. Studies on the structural, chemical and thermal properties of the crystal have been carried out on the basis of X-ray diffraction (XRD), infrared spectroscopy (IR), carbon, hydrogen, nitrogen (CHN) analysis, thermogravimetric (TG) analysis and differential thermal analysis (DTA) measurements. IR absorption bands indicate the mode of vibrations of different molecular groups present in LAHCl. TG-DTA analysis gives an idea about the thermal behaviour of LAHCl and ruled out the possibility of structural changes independent of mass changes.     

Synthesis of ZnO single crystals by the flux method

Zinc oxide (ZnO) single crystals have been grown at temperatures ranging from 450–900 °C and for 1–12 h, using hydrous KOH and NaOH melts as fluxes. For a KOH flux, brown ZnO single crystals with diameter 0.5 mm × 7.5 mm were grown under conditions of 500 °C for 20 h and white crystals of diameter 0.5 mm × 7 mm were grown at 800 °C for 20 h, using a small crucible (average 50 ml). When a large crucible (average 400 ml) was used, ZnO single crystals with diameter 0.5 mm × 8 mm were formed at 900 °C for 30 h. When using a KOH + NaOH (1∶1) flux, light-brown and long crystals with diameter 1.0 mm × 18 mm could be grown. The grown ZnO single crystals were bounded with only both p- and m-faces. It seems that crystal qualities were good under conditions of 900 °C for 30 h. The following mechanisms of dissociation and formation of ZnO single crystal from KOH (or NaOH) + ZnO melt seemed to occur $$KOH(or{\text{ NaOH}}){\text{ }} \to {\rm K}^ + {\text{ (or Na}}^{\text{ + }} {\text{) + OH}}^ - $$ $$ZnO{\text{ + 2 OH}}^ - \to {\text{ ZnO}}_{\text{2}}^{{\text{2}} - } {\text{ + H}}_{\text{2}} {\text{O,}}$$ $${\text{ZnO}}_{\text{2}}^{{\text{2}} - } {\text{ }} \to {\text{ ZnO + O}}^{{\text{2}} - } .$$      

Structural,optical, electrical properties of new hybrid organic–inorganic NLO single crystal: bis(1H-benzotriazole) hexaaqua-zinc bis(sulfate) tetrahydrate (BZS)

A new hybrid organic–inorganic nonlinear (NLO) single crystal, Bis(1H-benzotriazole) hexaaqua-zinc bis(sulfate) tetrahydrate (BZS), has been successfully synthesized and the single crystals were grown by slow evaporation solution growth technique (SESG) using Millipore water as a solvent. The structure of the BZS crystal was solved and refined by single-crystal X-ray diffraction and demonstrates that the grown crystals belong to a triclinic system with the space group P-1. The asymmetric part of the titled compound contains isolated organic cation (C₆H₆N₃)₂, metallic cation [Zn(H₂O)₆]²⁺, sulfate anion (SO₄)^2? and free H₂O molecules. The interplay between the wide number of intermolecular interaction such as O–H···O, N–H···O, C–H···O and π–π stacking interactions were discussed. The optical transmittance spectrum shows that the crystal is excellent transmittance in the entire Vis–NIR region with the cutoff wavelength at 345 nm. The presences of expected functional groups were identified by Fourier transform infrared spectroscopy. The dielectric measurements were carried out at different temperature in the frequency range 100 Hz–5MHz. Furthermore, the studies of its third-order NLO properties using a Z-scan technique demonstrate that the BZS crystal possesses a strong reverse saturable absorption (RSA) and the self-focusing (SF) nature with large second order hyperpolarizability (γ?=?6.24?×?10^?34 esu). All the results indicate that BZS crystal might be the potential candidate for the third-order NLO applications.     

A study on the <Emphasis Type="SmallCaps">l</Emphasis>-lysine-iodic acid: semi organic non linear optical single crystals for electro-optic applications

Non linear optical single crystals of l-lysine-iodic acid (LLI) of dimensions upto 24?×?14?×?5 mm³ have been grown successfully by slow evaporation technique from aqueous solution. The crystal structure of the grown material was solved by single crystal X-ray diffraction analysis and it was found that the LLI crystal belongs to monocinic system with space group P2₁. Functional groups of the grown crystal were identified by Fourier Transform Infrared (FTIR) spectral analysis. The UV–Vis spectral analysis was carried out to measure the transparent range of the LLI crystal which is nearly 85% and the band gap energy is found to be 5.51 eV. Thermal stability and decomposition temperature of LLI crystal was found by means of TGA and DTA analyses. The mechanical behavior of the grown crystal has been employed using Vicker’s micro hardness technique. The Second Harmonic Generation (SHG) efficiency of the crystal was investigated and it was found to be 3.2 times of KDP. The particle size dependent SHG studies of LLI crystals were performed using Nd:YAG laser. The laser damage threshold value of LLI crystal is found to be 8.54 GW/cm². Dielectric study indicates the reasonable dielectric constant and low dielectric loss of LLI crystal which are essential properties to develop optoelectronic devices. The ac and dc electrical conductivity measurements were carried out at various temperatures. Photoconductivity study exhibits the negative photoconductivity nature of the LLI crystal and the results are discussed for the first time.     

A new flux for the fast growth of potassium titanyl phosphate (KTP) single crystals

Single crystals of the non-linear optical material KTiOPO₄ (KTP) have been grown using a new KBa₂(PO₃)₅?2K₂O flux, which produced faster growth than existing fluxes. Crystals of size 6 mm×4 mm×2 mm were grown from the flux in a day. Perhaps relatively large crystals may be grown commercially in a short time.     

Crystal growth of cesium triborate, CsB3O5 by Kyropoulos technique

Large single crystals of CsB₃O₅ (CBO), free of cracks and inclusions, were successfully grown by the Kyropoulos technique from a slightly Cs₂)-enriched melt. The growth conditions were experimentally established. Maximum dimensions obtained were 45×41×44 mm fora×b×c-axes. Optical uniformity of these as-grown crystals was verified by means of striation observation, and the optical transparency characteristic was measured in the region from vacuum ultraviolet (VUV) to infrared (IR) wavelengths.     

Sublimation epitaxy of AlN layers on 4H-SiC depending on the type of crucible

Epitaxial layers of aluminum nitride ≤335 μm thick have been grown at temperatures of 1900 and 2100 °C on 10×10 mm² (0 0 0 1)-oriented α(4H) silicon carbide (SiC), with growth times of 1 and 4 h, via sublimation-recondensation in a RF-heated graphite furnace. The source material was polycrystalline AlN. The sublimation process was performed in three types of graphite (C) crucible: C1, C2 with inner diameters of 35 and 51 mm, respectively, and C3 with the same inner diameter as C1, but coated with a layer of TaC. The surface morphology reflects the hexagonal symmetry of the substrate, suggesting an epitaxial growth for samples grown in C1 and C3 crucibles for all growth conditions. The same symmetry is observed for AlN layers grown in the C2 crucible, but only at 2100 °C. X-ray diffraction analyses confirm the epitaxial growth of AlN samples with the expected hexagonal symmetry. A high-resolution X-ray diffractometer was used to assess the quality of the single crystals. A full width at half maximum of 242 arcsec was achieved for an AlN layer grown in the crucible coated with TaC.     

Growth and characterization of Na3BaCl5·2H2O

Na₃BaCl₅·2H₂O crystals were prepared by the slow evaporation of an aqueous solution of a mixture of sodium chloride and barium chloride in stoichiometric ratio. Crystals were found to possess platelet habit. Crystals were analysed by infrared spectrophotometry, thermogravimetry and X-ray diffraction. The appearance of bands due to stretching and bending modes of water molecules in the IR spectra showed that the grown crystals were hydrated. X-ray oscillation and Weissenberg photographs were used to measure the dimensions of the unit cell.     

Growth and some properties of barium-cadmium formate single crystals: (I) Crystal growth and morphology

The growth of barium-cadmium formate BaCd(HCO₂)₄·2H₂O single crystals by slow cooling method and their characterization by selective etching are reported. It was found that BaCd(HCO₂)₄·2H₂O crystallizes from aqueous solution in 2/m class of the monoclinic system. Crystals grown during a period of 1 month have dimensions of about 2 × 1.5 × 10 cm³. The typical twinning for these crystals has been observed and investigated by the selective etching. The dislocation density has been estimated to be 3·10² – 2·10³ cm^?2.     

Doping effect of urea on growth,spectral, thermal,mechanical, electrical,nonlinear and optical studies of Sr(HCOO)<Subscript>2</Subscript>·2H<Subscript>2</Subscript>O crystal: enhanced third-order NLO properties with a high laser-induced damage threshold

Pure and urea doped (with 3 different concentrations, viz. 0.005, 0.05, and 0.1 M) strontium formate dihydrate (SFD, Sr(HCOO)₂·2H₂O) single crystals were grown from aqueous solutions by using slow solvent evaporation technique. In order to understand the effect of urea doping on the structural, chemical, thermal, morphological, optical properties of SFD crystals, the grown crystals were characterized by carrying out CHN analysis, powder X-ray diffraction, high resolution X-ray diffraction, Fourier transform infrared spectral, thermogravimetric, UV–Vis–NIR spectral, photoluminescence spectral, second harmonic generation efficiency, and Z-scan measurements. The results obtained indicate that the urea molecule have entered into the SFD crystal matrix and has improved the crystallinity. Also, the results indicate that urea doping significantly tunes the optical and thermal properties without significantly distorting the crystal structure of SFD crystal. The laser damage threshold (LDT) energy for the grown crystal has been measured by using a Q-switched Nd:YAG laser as a source in single-shot mode (1064 nm, 10 Hz, 420 mJ). The result of laser damage threshold (LDT) energy indicates that grown title crystal has excellent resistance to laser radiation than those of some known inorganic NLO materials. Its third-order nonlinear optical properties were investigated by Z-scan technique and proved that the grown crystal possesses two-photon absorptions (TPA) and the self-defocusing effect.     

Enhanced optoelectronic,thermal, mechanical and third order nonlinear optical properties of dichlorobis(thiourea)zinc(II) crystal: an effect of Phenol red dye

For the first time the growth of dichlorobis (thiourea) zinc(II) (ZTC) monocrystal in presence of Phenol red dye of considerably good size (~13 mm?×?5 mm) has been achieved from aqueous solution using slow evaporation solution technique at room temperature. The solubility was calculated at different temperatures. The crystal structure was confirmed through X-ray diffraction analysis. The crystallinity of the dyed crystals has been enhanced revealed by Powder X-ray diffraction study. The presence of dye was inveterate by FT-IR and FT-Raman spectroscopic studies. The scanning electron microscopy analyses show that the grown crystals with dye are better than pure. Diffused reflectance was measured and optical band gap was calculated found to be enhanced from 4.5 to 4.65 eV for dyed crystals. The enhancement in the PL intensity has been observed in the dyed crystals. DSC study shows that the thermal stability has been remarkably enhanced from 163?°C (pure) to 203?°C (dyed) and various other thermal parameters are calculated. The surface study shows that the grown crystals with dye possess less dislocation than pure. Mechanical strength of the dyed crystal is found to be remarkably enhanced. Third-order nonlinear optical susceptibility (χ3) of PRZTC was found to be 2 times higher than pure. All results suggest that the properties of ZTC crystals grown in presence of dye are enhanced and can be considered as better contender in various nonlinear devices.     

Anisotropic photoresponse investigation of chemical vapor transport (CVT) grown quaternary Cu2ZnSnS4 single crystals

The single crystals of quaternary transition metal chalcogenide Cu₂ZnSnS₄ (CZTS) are grown by a closed system chemical vapor transport technique. The high purity individual elemental precursors are employed in the growth of the crystals. These crystals are found to be single-phase by X-ray diffraction and Raman analysis. The near stoichiometry of the grown crystals is confirmed by spectroscopy analysis of the photoelectron generated by X-rays and analysis of the energy of the dispersive X-rays generated by electrons. The surface study by scanning electron microscopy showed the growth to happen by sheet spread mean and the electron diffraction showed fringe width match with (112) plane spacing. The study of the CZTS/Ag-paste/Cu-wire system for incident white light and three wavelengths of laser lights in two configuration modes of top-contact (II to the plane) and bottom-top-contact (⊥ to the plane) showed anisotropic behavior. The incident white light illumination intensity of 120 mW/cm² showed utmost photoresponse. The top-contact mode configuration showed maximum responsivity and detectivity of 0.72 mA/W and 0.33 × 10⁹ Jones, respectively, while bottom-top-contact showed 0.18 mA/W and 0.13 × 10⁹ Jones, respectively. The anisotropic photoresponse by the CZTS crystals insinuates the potential for future applications.

     

Physical properties of lauric acid crystals grown with KBr in aqueous solution

Lauric acid crystals were grown with potassium bromide (LAPB) in aqueous solution at room temperature by slow solvent evaporation technique. The monoclinic structure of grown single crystal was studied by single-crystal X-ray diffraction and powder X-ray diffraction analyses. The Fourier transform infrared spectrum incorporates signatures of functional groups. The optical absorbance study reveals the UV cut-off wavelength as 230 nm. The Kurtz powder technique ensures that LAPB crystal has 1.1 times greater second harmonic generation efficiency than that of KDP crystals. The thermo-gravimetric and differential thermal analyses ensure that the material has good thermal stability. A dielectric behaviour of the sample material is studied in the frequency range \(10^{1}\)–\(10^{6}\)  Hz.     

Characterization of gel-grown neodymium heptamolybdate crystals

Neodymium heptamolybdate crystals grown from silica gels [1] are characterized em ploying energy dispersine X-ray analysis, X-ray and electron diffraction, infra-red spectroscopy, optical microscopy and scanning electron microscopy techniques and the results obtained are presented. The crystals are established to have the composition Nd₂Mo₇O₂₄27H₂O. The results of electron diffraction studies indicate the material to be thermally unstable. The crystals growing within the gel medium exhibit varied morphologies including square and octagonal platelets, cuboids, multifaceted crystals, coalesced and aggregated forms and spherulites. The spherulitic morphology is shown to arise due to crystallites adhering in a spherical envelope and are not as a result of crystal fibres radiating out from a centrally located common nucleus. The morphology of the building blocks of the crust at the gel reactant interface is discussed.     

Fe2O3的掺杂对TSSG法生长Zn:Fe:LiNbO3 晶体的结构和光折变性能的影响

本文利用TSSG方法生长了不同掺Fe2O3浓度的Zn∶Fe∶LiNbO3晶体,并对晶体进行了红外光谱、紫外光谱、晶格常数和居里温度的测试和分析.利用二波耦合实验测得的写入和擦除曲线,计算了晶体的写入时间常数、擦除时间常数和最大衍射效率.并讨论了Fe2O3的掺杂对材料结构和光折变性能的影响机制.     

Growth and characterization of RuO2 single crystals

Using the vapor transport technique in a flowing oxygen system, we have grown the largest single crystals of RuO₂ ever reported (10 mm × 5 mm × 5 mm). Polycrystalline RuO₂, a mixture of polycrystalline RuO₂ and purified Ru metal powder, or purified Ru metal powder were used as the starting material. Optimum conditions are given for growing large high quality crystals. The morphology, stoichiometry and resistivity of selected single crystals of RuO₂ are discussed.     

Growth and characterisation of TaS2 single crystals

Single crystals of tantalum disulphide have been grown by a sublimation or direct vapour transport method. Crystals as large as 15×10×0·05 mm³ grew in the form of platelets and needles above the charge which was kept well distributed within the ampoule. Characterisation of the as-grown crystals has been carried out at room temperature by x-ray diffraction. Electrical conductivity and magnetic susceptibility measurements have also been made.     

Lepidocrocite-like TiO2 and TiO2(110)–(1 × 2) supported on W(100)

Ultrathin films of TiO₂ were grown on a W(100)–O(2?×?1) substrate and characterised with a combination of scanning tunneling microscopy (STM) and low energy electron diffraction. In addition to islands of rutile TiO₂(110) with (1?×?1) termination that were reported previously, we also observed rutile TiO₂(110) islands with a (1?×?2) film termination. A lepidocrocite-like TiO₂ nanosheet was also observed on the W(100) surface. High resolution STM images show that the nanosheet grows in the principal orthogonal directions of the W(100) substrate and forms a commensurate (1?×?7) coincident cell.