Synthesis of spindle‐shaped α‐FeOOH and α‐Fe2O3 nanocrystals

Spindle‐shaped α‐FeOOH nanocrystals were facilely synthesized using a poly (vinyl pyrrolidone) (PVP)‐assisted route under hydrothermal conditions. The chemical compositions and morphol‐ogies of the as‐prepared samples were characterized in detail by X‐ray power diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscope (TEM). The experimental results reveal that these spindle‐shaped α‐FeOOH nanocrystals have self‐organized into assemblies with hierarchical nanostructures. The crucial roles of PVP in the hydrothermal synthesis of hierarchical α‐FeOOH nanostructures were discussed. The possible formation mechanism was also suggested. Moreover, the spindle‐shaped α‐Fe₂O₃ nanocrystals could be easily obtained after calcining the α‐FeOOH prepared by the PVP‐assisted hydrothermal process. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structural and optoelectrical properties of Ga‐doped ZnO semiconductor thin films grown by magnetron sputtering

Transparent conductive gallium‐doped zinc oxide (Ga‐doped ZnO) films were prepared on glass substrate by magnetron sputtering. The influence of substrate temperature on structural, optoelectrical and surface properties of the films were investigated by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), spectrophotometer, four‐point probe and goniometry, respectively. Experimental results show that all the films are found to be oriented along the c‐axis. The grain size and optical transmittance of the films increase with increasing substrate temperature. The average transmittance in the visible wavelength range is above 83% for all the samples. It is observed that the optoelectrical property is correlated with the film structure. The Ga‐doped ZnO film grown at the substrate temperature of 400 °C has the highest figure of merit of 1.25 × 10⁻² Ω⁻¹, the lowest resistivity of 1.56 × 10⁻³ Ω·cm and the highest surface energy of 32.3 mJ/m².     

PbS crystals with clover‐like structure: Preparation,characterization, optical properties and influencing factors

A new and simple route to synthesize Lead sulfide (PbS) crystals with the clover‐like structure was described in the current paper. PbS was prepared in a simple aqueous solution employing (CH₃COO)₂Pb and thiourea as the initial materials under 130 W microwave irradiation. No any surfactant or template including organic polyamines with N‐chelation property was needed. The phase and composition of the product were identified by X‐ray powder diffraction (XRD) and X‐ray photoelectron spectra (XPS). TEM observation showed that the product with the six‐petal flower‐shaped structures was obtained, but SEM observation confirmed the clover‐like structure of the product; and the six‐petal flowers were formed via the overlap of two clovers revolved 60° around the center of the flower. Some factors affected the shape of the final product were studied and the optical properties of PbS crystals with the clover‐like structure were measured. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth of spindle‐shaped silver nanoparticles in SDS solutions

Spindle‐shaped silver nanoparticles were successfully prepared in high yield by a simple wet chemical approach using citric acid (CA) as reducant in the presence of sodium dodecyl sulfate (SDS) at room temperature. Transmission electron microscopy (TEM), UV‐vis absorption spectroscopy and X‐ray diffraction (XRD) have been used to characterize the obtained products. It is found that the spindle‐shaped architecture of siver nanoparticles is drastically influenced by the mass ratio of SDS to CA and the concentration of silver nitrate (AgNO₃). It is revealed that SDS is not as a template but as a capping agent. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Facile fabrication of porous ZnO by a template free method

In this paper, a template free method has been employed to fabricate porous ZnO. Brick shaped precursor was first synthesized by a mild hydrothermal process. Accompanied with the decomposition of the precursor during the subsequent annealing treatment, porous ZnO with the inherited morphology of the precursor was obtained. The as‐prepared products were characterized by X‐ray diffraction (XRD) and scanning electron microscopy (SEM). It exhibited that the porous hierarchical frame consists of nano‐sheets with wurtzite‐type. The size of the pores as well as the size of the particles varied with the annealing temperature. Mechanism speculation showed that the crystal‐aggregation in the growth process of the precursor is the key to the establishment of pore structure. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Shape diversity in particles obtained by low temperature pyrolysis of ferrocene

Synthesis experiments, made in a hermetically closed steel container through pyrolytical decomposition of various mixtures like ferrocene and xylene; ferrocene and water; ferrocene, xylene and water in different ratios have resulted in emergence of different in shape particles. The necessary for the realization of each experiment temperature increases linearly with 20 K/min up to the needed temperature and decreases mostly with no delay with a cooling rate of 30 K/min down to room temperature. The obtained particles are shaped as spheres, entirely or partially finished octahedrons or resemble stars. The spheres are perfect in shape and consist of pure incompletely graphitisized carbon. The octahedron and star‐like shaped particles, synthesized in the presence of ferrocene as precursor, have magnetite nuclei and carbon coating. Particle morphology has been examined by Scanning (SEM) and Transmission Electron Microscopy (TEM) and their chemical composition and crystal structure by the means of X‐ray diffraction (XRD), Mössbauer spectroscopy and Electron Probe X‐ray Micro Analysis and Energy Dispersive X‐ray Spectrometry (EDS). Based on the results obtained it has been concluded that the synthesized particle morphology depends on the simultaneous proceeding magnetite crystal growing and crystal coating with partially graphitisized carbon deposit. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal growth,optical and luminescence properties of (Ce,Sr)‐doped PrAlO3 single crystals

Using the micro‐pulling‐down method, (Ce,Sr)‐doped PrAlO₃ square‐shaped single crystals (4×4×12 mm) were grown. Structural parameters studied by X‐ray powder diffraction were consistent with R3m space group. Compositional homogeneity was checked with electron probe micro‐analysis and found quite uniform. Absorption spectra and luminescence characteristics under UV and X‐ray excitations were measured at room temperature with no Ce‐related emission appeared. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

BaMoO4 thin films prepared by electrochemical method at room temperature

Highly crystallized BaMoO₄ films were prepared on molybdenum substrates in Ba(OH)₂ solutions by electrochemical method at room temperature. The deposition conditions (reaction temperature and current density) during electrochemical formation were researched. The films were characterized by using the X‐ray Diffraction (XRD), Scanning Electronic Microscopy (SEM) and X‐ray Photoelectron Spectroscopy (XPS) analyses. The XRD analyses show that the films are good crystalline with single scheelite‐type tetragonal structure; the SEM photographs show that the films are densely deposited with double tetragonal tapers in shape; and the XPS analyses reveal that the composition of the BaMoO₄ films (embodied Ba²⁺, Mo⁶⁺ and O^2‐) is in agreement with stoichiometry. The optimum electrochemical conditions for BaMoO₄ films formation are the lower reacting temperature (near room temperature) and the feasible current density (about 1mA/cm²)     

Preparation,physicochemical and third order nonlinear optical properties of bis(tetrabutylammonium)bis(2‐thioxo‐1,3‐dithiole‐4,5‐dithiolato)mercurate(II)

Bis(tetrabutylammonium)bis(2‐thioxo‐1,3‐dithiole‐4,5‐dithiolato)mercurate(II) was prepared and characterized by elemental analyses, electronic absorption, infrared and X‐ray powder diffraction spectroscopy. The specific heat of the crystal was measured to be 1878.2 J.mol^–1K^–1 at 300 K. The thermal decomposition process was investigated by means of thermogravimetric analysis and differential thermal analysis measurements in air together with infrared and X‐ray powder diffraction spectra. The third‐order nonlinear optical properties at 800 nm were measured by femtosecond optical Kerr gate technique by using CS₂ as reference. The third‐order optical susceptibility of its acetone solution at the concentration of 9.27 × 10^–4 M was obtained to be 2.53 × 10^–14 esu. The second‐order hyperpolarizability was estimated to be 1.7 × 10^–32 esu and the response time was about 226 fs. The third order nonlinear optical properties at 532 nm were investigated by using the Z‐scan technique with 20 ps. It exhibited self‐focusing effect and saturable absorption. The second molecular hyperpolarizability was estimated to be 8.4 × 10^–32 esu. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of substrate temperature on structural and materials properties of zirconium nitride films on D9 steel substrates

Thin zirconium nitride (ZrN) films were prepared by using reactive direct current (DC) magnetron sputtering onto D9 steel substrates. XRD technique was employed to study the coatings, observing variations of crystallite size, crystallite texture and lattice constant, as a function of substrate temperature. Chemical states of the ZrN thin films were determined by X‐ray photoelectron microscopy (XPS). AFM picture showed the presence of spherical shaped grains on the top of homogeneous granular surface. The hardness and elastic modulus values were measured by nanoindendation and their values are 18.5 and 343 GPa respectively. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Magnetic properties and X‐ray photoelectron spectroscopy of nanocrystalline Ho3Al5O12

Nanocrystalline holmium aluminium garnet (Ho₃Al₅O₁₂) has been prepared for the first time by modified Pechini's reaction after sintering the precursor gel at 1223 K. The nanomaterial has been characterized by X‐ray diffraction (XRD), selected area electron diffraction (SAED) and high resolution transmission electron microscopy (HRTEM). The XRD pattern confirms the formation of single‐phase Ho₃Al₅O₁₂; the average size of the nanoparticles has also been determined. X‐ray photoelectron spectroscopy (XPS) has been used to study the chemical composition and bonding in the as‐prepared samples. The binding energies of core‐level electrons in Ho, Al and O in the title material have been found slightly shifted compared to the values of the respective elements. DC magnetic susceptibility has been measured in the temperature range 2 – 260 K. Low effective magnetic moment of Ho³⁺, μ_eff = 1.35 µ_B and Weiss constant have been derived from the inverse magnetic susceptibility–temperature linear plot. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal growth,quality characterization and THz properties of DAST crystals

4‐N, N‐diethylamino‐4’‐N’‐methyl‐stilbazolium tosylate (DAST) crystals were grown by slope nucleation method (SNM). The crystal structure of grown DAST crystals was characterized by single crystal X‐ray diffraction with demonstrating X‐ray diffraction main peaks. The crystal defects were analyzed by the synchrotron radiation X‐ray topography. It was found that the unbalanced temperature gradient, the Teflon groove and the super saturation fluctuation were primary causes of crystal defects. Furthermore, widely tunable THz waves ranging from 1.16 to 16.71 THz were generated from 1 mm‐thick DAST crystal using the optical parametric oscillator (OPO). It was obtained that the THz output energy was 27.4 nJ (peak power of 2.74 W) and the highest conversion efficiency was 1.37 × 10⁻⁵ at 3.8 THz.     

Single‐crystal sapphire microstructure for high‐resolution synchrotron X‐ray monochromators

We report on the growth and characterization of sapphire single crystals for X‐ray optics applications. Structural defects were studied by means of laboratory double‐crystal X‐ray diffractometry and white‐beam synchrotron‐radiation topography. The investigations confirmed that the main defect types are dislocations. The best quality crystal was grown using the Kyropoulos technique. Therein the dislocation density was 10²–10³ cm⁻² and a small area with approximately 2*2 mm² did not show dislocation contrast in many reflections. This crystal has suitable quality for application as a backscattering monochromator. A clear correlation between growth rate and dislocation density is observed, though growth rate is not the only parameter impacting the quality.     

Growth and characterization of Bis Thiourea Zinc Acetate (BTZA)

Single crystals of BTZA have been grown by low temperature solution growth method using slow cooling process at an optimized pH of 3.5. The grown crystals have been examined under an optical microscope to study its surface morphology. The morphological studies show that the growth takes place by spreading of growth layers. Formation of rectangular shaped etch pit on the as‐grown crystal has been explained in relation to the growth conditions. Single crystal X‐ray diffraction analysis has been carried out to confirm the monoclinic system. Transmission spectrum reveals that the crystal has a low UV cut off of 434.5 nm and has a transmittance of 100%. Dependence of micro hardness on load has been studied. Powder X‐ray Diffraction and FT‐IR have been carried out to characterize the grown crystals. BTZA forms metal – sulfur bond and has good optical transmission in the entire visible region, which is the essential requirement for a non‐linear crystal. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Dopant induced morphologies of ZnS nanoparticles

We have reported the synthesis of cubic (zinc blende) phase ZnS: Ni²⁺ nanoparticles using a simple wet‐chemical method. Synthesized ZnS: Ni²⁺ nanoparticles had been characterized by X‐ray diffraction (XRD) and Energy Dispersive X‐ray (EDX) analysis. Surface morphologies were studied using Scanning Electron Microscopy (SEM). Fourier Transform Infrared (FTIR) spectra of selected samples were also carried out to confirm the presence of capping agent on the surface of the material. We have demonstrated that various morphologies like spherical, tetrapods, sheet and long‐armed multipods are emerged by simple chemical route without any vigorous reaction parameters and changing the concentration of dopant ions only. The probable mechanism for such morphologies has also been suggested.     

Effect of substrate temperature on the properties of reactively sputtered TiN/NbN multilayers

TiN/NbN multilayer coatings were deposited with various substrate temperatures by DC reactive magnetron sputtering method onto Si (111) and glass substrates. The effect of substrate temperature on the structural and optical properties of TiN/NbN multilayers was investigated by X‐ray diffraction, X‐ray photoelectron spectroscopy, Field emission scanning electron microscopy and Photoluminescence measurements. The composition was analyzed by X‐ray photoelectron spectroscopy. X‐ray diffraction results showed that the layers crystallized in cubic structure for TiN and hexagonal structure for NbN. It was found that grain size increased with increase in substrate temperature. The surface morphology of the TiN/NbN thin films showed a dense and smooth surface with substrate temperature upto 200 °C but after 300 °C, the grains became larger and coarse surface was observed. The TiN/NbN multilayer coatings exhibited the characteristic peaks centered at 180, 210 and 560 cm^‐1. Red band emission peaks were observed in the wavelength range of 700‐710 nm. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Mott‐hopping processes in neodymium oxide thin films prepared on Si(100) substrates

Thin Nd oxide films were prepared on Si (P) substrates to form MOS structure. The oxide films were annealed at different conditions and their crystal structures were determined by X‐ray diffraction (XRD). The dc electrical transport properties of the devices with amorphous and crystalline Nd oxide were investigated. The current‐temperature J(T) characteristics suggest that the carrier transport through the insulator follows Mott's variable‐range hopping (VRH) mechanism and its results were compared with the results obtained from X‐ray diffraction. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Zr‐doped CeO2 Hollow slightly‐truncated nano‐octahedrons: One‐pot synthesis,characterization and their application in catalysis of CO oxidation

Zirconium‐doped ceria hollow slightly‐truncated nano‐octahedrons (HTNOs) (Ce_1‐xZr_xO₂) were synthesized by a one‐pot, facile hydrothermal method. The morphology and crystalline structure were characterized with powder X‐ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and the high resolution transmission electron microscopy (HRTEM). The composition and chemical valence on the surface of the as‐prepared Ce_1‐xZr_xO₂ powders were detected by X‐ray photoelectron spectroscopy (XPS) and energy dispersive spectrometry (EDS). The surface area and pore size distribution of as‐obtained Zr‐doped ceria HTNOs were measured by N₂ adsorption‐desorption measurement. Mechanisms for the growth of Zr‐doped ceria HTNOs are proposed as both oriented attachment and Ostwald ripening process and the formation of the hollow structure is strongly dependent on the addition of Zr⁴⁺ ions. Furthermore, the as‐obtained Zr‐doped ceria HTNOs revealed superior catalytic activity and thermal stability toward CO oxidation compared to pure ceria. It may provide a new path for the fabrication of inorganic hollow structures on introducing alien metal ions.     

Photoconduction and transport mechanisms in polycrystalline zincphthalocyanine thin films

Zincphthalocyanine (ZnPc) thin films were prepared by the vacuum evaporation method under a pressure of 10^‐6 mbar. The X‐ray diffraction analysis of vacuum evaporated ZnPc films reveals that the structure of the films is polycrystalline in nature. The photoconduction properties have been studied in the wavelength range 400 –800nm using suitable masks. The Photoconductivity of the films as a function of light intensity and applied voltage were studied and results were discussed in detail. The photoconduction was found to increase with higher light illumination and maximum at the band edge of the ZnPc thin film. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

An X‐ray powder diffraction study of the microstructural evolution on heating 3:2 and 2:1 mullite single‐phase gels

Single‐phase gels with compositions 3Al₂O₃·2SiO₂ and 2Al₂O₃·SiO₂ were prepared by gelling mixtures of aluminium nitrate and tetraethylorthosilicate. Gels were fast heated at different temperatures between 900°C and 1600°C. The phase transformation and microstructural changes of both mullite precursor gels over the temperature range were followed by X‐ray powder diffraction (XRD), lattice parameter determination (LP), and scanning and transmission electron microscopies (SEM and TEM). The distribution of crystallite sizes and strains were determined by linewidth refinements of X‐ray diffraction patterns using the integral breadth method of Langford and the Warren‐Averbach analysis. XRD of both heated gels showed the formation of crystalline mullite single phase. Some amount of glassy phase coexisted with mullites at low temperatures, i. e. below 900°C. The compositional range of mullites formed on heating gels at temperatures between 900°C and 1600°C was dependent on the starting nominal composition of gels. SEM and TEM micrographs of both heated gels below 1200°C showed the formation of small, discrete, prismatic, well‐shaped nanocrystals in a very ordered arrangement. The size of these nanocrystals was dependant on the nominal composition of gels and increased on rising the heating temperature of gel precursors. The microstructural features obtained from linewidth refinement results of X‐ray diffraction patterns also allowed to suggest the formation of prismatic a little elongated nanocrystals at temperatures below 1200°C. Microstrain values were small and only displayed a relatively significant value for mullites processed at 900°C. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)