Crystal growth and characterization of CuI single crystals by solvent evaporation technique

Cuprous iodide (CuI) crystals are grown by slow evaporation technique in three different solvents. Large CuI single crystals with dimensions of 7.5 mm × 5 mm × 3 mm are obtained in pure acetonitrile solvent at 40 °C. The as-grown crystals are analyzed by X-ray diffraction, energy-dispersive X-ray analysis, differential scanning calorimetry, current-voltage characteristic and photoluminescence spectrum. The results show that the CuI crystal has the zinc-blende structure with no secondary phase. The elemental Cu/I ratio is 1.09:1. The melting point of the crystal is 875 K and two phase transitions occur from room temperature to its melting point. The electrical conductivity of CuI platelet crystal is in the range of 1.11-2.38 Ω⁻¹ cm⁻¹. Under ultraviolet excitation, the CuI crystals exhibit three emission bands with peak positions at 426, 529 and 671 nm. The nature of the luminescence is discussed.     

Growth, characterization and optical quality of CaF2 single crystals grown by the temperature gradient technique

The CaF₂ single crystals with diameters up to 200 mm were successfully grown by modified temperature gradient technique (TGT), which are suitable for application as optical elements in the ultraviolet range. The optimizations of various growth parameters were systematically studied. Properties of as-grown CaF₂ crystals were characterized by the nature of inclusions, dislocations, crystallinity, and impurities contents. The results showed that the dislocations and multinucleation were mostly constrained in the conical part of the crystals with the cylindrical parts having the best crystalline quality and lowest impurity contents. The high optical quality of TGT-grown CaF₂ single crystals was also confirmed to have excellent optical transmission in 190-2500 nm and refractive index homogeneity.     

Study of optimum growth condition and characterization of zinc mercury thiocyanate (ZMTC) single crystals in silica gel

Some bimetallic thiocyanate complexes exhibit excellent nonlinear optical properties. Single crystals of one such material, zinc mercury thiocyanate ZnHg(SCN)₄ have been grown in silica gel with gel technique by the process of diffusions and the optimum growth condition has been studied. Crystals of 4 mm length have been obtained. Their structural, optical and thermal properties have been studied. Structural analysis was carried out using an X-ray diffractometer and the crystal structure was confirmed to be tetragonal. Fourier transform infrared spectrum was obtained to confirm the functional groups. Transmission spectrum has been recorded in the solution state and the cut-off wavelength has been determined. Thermal stability of the grown crystal has been investigated by thermogravimetric and differential thermal analyses. Nonlinear optical property of the crystal has been confirmed using the Kurtz powder technique and a study of its second harmonic generation efficiency in comparison with urea has been made.     

Synthesis and characterization of pure,urea and thiourea doped organic NLO l-arginine trifluoroacetate single crystals

Optically transparent l-arginine trifluoroacetate (LATF) single crystals by doping with organic materials urea and thiourea were grown by slow solvent evaporation technique. Powder X-ray diffraction confirms improvement in the crystalline quality for urea doped crystals. Urea doping in LATF also improves the percentage of transmittance. The vibrational frequencies of the grown crystals were assigned by Fourier Transform infrared spectroscopy. The thermal analysis (TG/DTA) indicated the better thermal stability for urea doped LATF crystals. EDAX analysis was carried out to calculate the percentage of elements present in doped and pure LATF. The hardness has been remarkably improved on urea and thiourea doped LATF crystals. The second harmonic generation (SHG) analysis showed 2.5 times than standard KDP for pure LATF and 2.2, 2.07 times than KDP for urea and thiourea doped LATF.     

Growth and electrical properties of mercury indium telluride single crystals

A novel photoelectronic single crystal, mercury indium telluride (MIT), has been successfully grown by using vertical Bridgman method (VB). The crystallinity, thermal and electrical properties of the MIT crystal were investigated. The results of X-ray rocking curve show that the as-grown MIT crystal has good crystal quality with the FWHM on (3 1 1) face of about 173 in. DSC measurement reveals that the Hg element is easy to solely evaporate from the compound when the temperature is higher than 387.9 °C in the open system. Hall measurements at room temperature show that the resistivity, carrier density and mobility of the MIT crystal were 4.79 × 10² Ω cm, 2.83 × 10¹³ cm⁻³ and 4.60 × 10² cm² V⁻¹ s⁻¹, respectively. The reduction of carrier mobility and the increase of the resistivity are related to the adding of In₂Te₃ into HgTe, which changes the energy band structure of the crystal.     

Effect of amino acid doping on the growth and ferroelectric properties of triglycine sulphate single crystals

Effect of amino acids (l-leucine and isoleucine) doping on the growth aspects and ferroelectric properties of triglycine sulphate crystals has been studied. Pure and doped crystals were grown from aqueous solution by low temperature solution growth technique. The cell parameter values were found to significantly vary for doped crystals. Fourier transform infrared analysis confirmed the presence of functional groups in the grown crystal. Morphology study reveals that amino acid doping induces faster growth rate along b-direction leading to a wide b-plane and hence suitable for pyroelectric detector applications. Ferroelectric domain structure has been studied by atomic force microscopy and hysteresis measurements reveal an increase of coercive field due to the formation of single domain pattern.     

The effect of growth conditions on the properties of ZnO nanorod dye-sensitized solar cells

In this article, we report ZnO nanorod samples grown on transparent conductive SnO₂:F (FTO) glass substrates by two different growth routes through hydrothermal method in a closed autoclave. One route is one-step continuous growth for 10 h. The other route is discrete multi-step growth for total 48 h. In this process, fresh solution was repeatedly introduced in every step. The structural, photoluminescence (PL) and photovoltaic properties of the as-prepared nanorod arrays were investigated. The nanorod arrays obtained through multi-step growth show longer rods, higher aspect ratio, larger spacing, better crystalline quality. The PL spectrum of nanorod arrays obtained through multi-step growth shows a strong and sharp near-band-gap emission (UV) peak and a weak green-yellow emission (GY) peak (I_UV/I_GY = 7.7), which also implies its good crystallinity and high optical quality. Dye-sensitized solar cells based on ZnO nanorod arrays were fabricated, and those grown with discrete multi-step procedure present better photovoltaic properties duo to its special morphology and better crystal quality.     

Hydrothermal preparation, characterization and property research of flowerlike ZnO nanocrystals built up by nanoflakes

In the present paper, flowerlike ZnO nanocrystals were successfully synthesized via a simple hydrothermal route in the presence of sodium dodecyl sulfate (SDS), employing Zn(CH₃COO)₂ and KOH as the starting reactants. The phase and morphology of the product were characterized by means of powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and select area electron diffraction (SAED). The optical properties of the product were studied. Some factors influencing the morphology of the final product including reaction time, temperature and amounts of the surfactant were discussed. Researches showed that the flowerlike ZnO nanocrystals had a good photo-catalytic activity for degradation of safranine T under 254 nm UV light irradiation. The electrochemical research of the product showed that flowerlike ZnO nanocrystals could promote electron transfers between catechol and the Au electrode. A possible formation mechanism was also suggested based on the results of the experiments.     

A novel and simple combustion route towards long legs nanotetrapod ZnO

The long legs nanotetrapod ZnO was synthesized by a novel combustion oxidization method without any catalyst or carrier gas at high temperature, different completely from any other thermal evaporation method. SEM and transmission electron microscopy (TEM) investigations show that the long legs nanotetrapod ZnO is high-quality single crystal. The as-synthesized product is high yield with the legs length of about 30-50 μm. Interestingly, these long legs of different nanotetrapod could be connected to each other via self-assembly under proper condition. The possible growth mechanism is discussed in detail.     

Growth and properties of benzil doped benzimidazole (BMZ) single crystals

In the present work, we have made an attempt to study the effect of benzil doping on the properties of benzimidazole single crystals. For this purpose we have grown pure and benzil doped benzimidazole single crystals by vertical Bridgman technique. The grown crystals were characterized by various characterization techniques. The presence of dopants confirmed by powder X-ray diffraction (XRD). Crystalline perfection of the grown crystals has been analysed by high-resolution X-ray diffraction (HRXRD). The transmittance, electrical property and mechanical strength have been analysed using UV-vis-NIR spectroscopic, dielectric and Vicker's hardness studies. The relative second harmonic generation efficiency of pure and doped benzimidazole crystals measured using Kurtz powder test.     

Preparation and characterization of porous Nb2O5 nanoparticles

Porous niobium oxide (Nb₂O₅) nanoparticles have been successfully prepared without any surfactant assisting. They were characterized by X-ray diffraction (XRD), nitrogen sorption, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The results show that the porous Nb₂O₅ nanoparticles are polycrystalline, the Brunauer–Emmett–Teller (BET) surface area is 12.09 m²/g and the average pore size is 3.4 nm. In addition, spherical and flake-like Nb₂O₅ samples were obtained and characterized. Possible explanations for the formation of Nb₂O₅ nanocrystals with different morphologies are discussed.     

Studies on Ag and Li ions irradiated LAHCl single crystals

Semi-organic single crystals of LAHCl were grown by unidirectional solution growth method. The grown single crystals were subjected to Ag⁸⁺ and Li⁴⁺ ions irradiation of energy 100 MeV and 50 MeV, respectively. Breaking of bonds in the irradiated LAHCl molecules and the lattice deformations are analyzed by Fourier transform infrared spectroscopy and X-ray diffraction studies, respectively. The modifications induced by ion irradiation in dielectric, mechanical stability and nonlinear optical property are studied at different ion fluence.     

Synthesis, characterization and optical properties of sheet-like ZnO

Sheet-like ZnO with regular hexagon shape and uniform diameter has been successfully synthesized through a two-step method without any metal catalyst. First, the sheet-like ZnO precursor was synthesized in a weak alkaline carbamide environment with stirring in a constant temperature water-bath by the homogeneous precipitation method, then sheet-like ZnO was obtained by calcining at 600 °C for 2 h. The structures and optical properties of sheet-like ZnO have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) and UV-vis-NIR spectrophotometer. The results reveal that the product is highly crystalline with hexagonal wurtzite phase and has appearance of hexagon at (0 0 0 1) plane. The HRTEM images confirm that the individual sheet-like ZnO is single crystal. The PL spectrum exhibits a narrow ultraviolet emission at 397 nm and a broad visible emission centering at 502 nm. The band gap of sheet-like ZnO is about 3.15 eV.     

Synthesis and photochromic properties of EDTA-induced MoO3 powder

In this study, the photochromic MoO₃ powder with novel morphology has been synthesized via hydrothermal method, using ethylene diamine tetraacetice acid (EDTA) as organic inducing agent. The influence of EDTA on the morphology, structure and photochromic properties of MoO₃ powder has been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), as well as ultraviolet and visible spectroscopy (UV-vis) and color difference meter. When the molar ratio of EDTA/Mo⁶⁺ is 0.05:1, the EDTA-induced MoO₃ powder is found to have 3D flower-like morphologies and excellent photochromic properties. Furthermore, the possible growth mechanism of the flower-like structure and the photochromic mechanism of MoO₃ powder are also discussed in detail.     

Synthesis of ZnO flowers and their photoluminescence properties

Flower-like ZnO nano/microstructures have been synthesized by thermal treatment of Zn(NH₃)₄²⁺ precursor in aqueous solvent, using ammonia as the structure directing agent. A number of techniques, including X-ray diffraction (XRD), field emission scan electron microscopy (FESEM), transmission electron microscopy (TEM), thermal analysis, and photoluminescence (PL) were used to characterize the obtained ZnO structures. The photoluminescence (PL) measurements indicated that the as-synthesized ZnO structures showed UV (∼375 nm), blue (∼465 nm), and yellow (∼585 nm) emission bands when they were excited by a He-Gd laser using 320 nm as the excitation source. Furthermore, it has been interestingly found that the intensity of light emission at ∼585 nm remarkably decreased when the obtained ZnO nanocrystals were annealed at 600 °C for 3 h in air. The reason might be the possible oxygen vacancies and interstitials in the sample decreased at high temperature.     

Synthesis and characterizations of nanoribbons and monodispersed nanocrystals of CuBr

Nanoribbons and monodispersed nanocrystals of CuBr have been prepared by a simple reaction between CuO suspension, NH₂OH·HCl and KBr in the presence of deionized gelatin at 10 °C. The products were characterized by X-ray powder diffraction, transmission electron microscopy and UV-vis absorption spectroscopy. The sizes of the monodispersed nanocrystals of CuBr were estimated by Debye-Scherrer formula according to XRD spectrum.     

Synthesis of hollow glass-ceramics microspheres via template method

Hollow glass-ceramics microspheres (HGCM) were successfully fabricated by a simple technique using polyacrylamide microspheres (PAM) as template. The corresponding HGCM were obtained by a thermal treatment of the core-shell microspheres, which were synthesized with organic template method. The effects of the concentration of glass powder, the Hydrophile-Lipophile Balance (HLB) value, and the amount of pre-adsorbed water on the morphologies of the core-shell microspheres and HGCM have been investigated. The size, morphology, core-shell structure and crystalline phase of HGCM and core-shell microspheres were determined via XRD, SEM and TGA. The influences of initiator and surfactant on the monodispersity and average diameter of PAM were investigated via SEM. The results showed that: (a) the average diameter and monodispersity of PAM can be controlled by varying the amount of initiator and surfactant, and (b) the agglomeration of core-shell microspheres and HGCM can be reduced using PAM with pre-adsorbed water and adjusting the HLB value. In addition, the amount of solid beads decreases obviously by reducing the concentration of glass powder and adjusting the HLB value.     

Hydrothermal preparation of PbS crystals and shape evolution

In the current paper, we successfully prepared lead sulfide (PbS) microcrystals with various shapes in a simple aqueous system using the hydrothermal synthesis route. Experimental results indicated that the change of the molar ratio of Pb²⁺/S₂O₃²⁻ could significantly influence the morphology of the product while keeping the other experimental conditions constant: with the decrease of the molar ratio of Pb²⁺/S₂O₃²⁻ from 1:1 to 1:4, the shape of the products varied from tri-prism, cube to magic-square structure. Changing the reaction temperature had big effect on the shape of the product: flower-shaped product was obtained at 80 °C and cube-shaped products were produced at 120 °C. When the reaction time varied, the shapes of the as-obtained PbS crystals also changed. At the same time, SEM observations showed that the counter-anions for Pb²⁺ could influence the shape of the product: Pb(NO₃)₂ being used as lead ion sources, most flower-shaped and few cubic PbS crystals were produced; while PbSO₄ as lead ion source, the PbS cubes were obtained. An evolution process was described based on experimental facts.     

Crystal growth and characterization of Deuterated Glycine Phosphite single crystals

Deuterated Glycine Phosphite single crystals were grown by low temperature solution growth method using high purity deuterated water as solvent. Deuteration content of the as grown crystals was improved by repeated recrystallisation process. Structural perfection, transparency and the functional groups present in the grown crystals were identified using different characterization analyses. Dielectric behaviors of the as grown specimens were examined through thermal and impedance analysis. Partial deuteration of the grown crystal was confirmed from the DSC and dielectric results.     

Low-temperature synthesis of leucite crystals using kaolin

Synthesis of leucite crystals below 1000 °C using natural kaolin as the primary raw material was investigated. Spherical leucite crystals having a diameter of approximately 50 μm were prepared by heating a powder mixture of Al₂(SO₄)₃, kaolin and K₂SO₄ (in mass ratios of 3:3:15) at 900 °C for 3 h. Quartz, the main accessory phase in kaolin, and the amorphous metakaolin formed upon heating kaolin were found to be responsible for the decreased synthesis temperature.