Structural and Thermal Characterization of Zeolite Type Y Modified by Ion Exchange with Zn,Cd, and Hg Cations

The object of our studies was zeolite NaY and its Zn²⁺-, Cd²⁺- and Hg²⁺ modifications obtained by ion-exchange method. Influence of the above cations on the crystalline structure of zeolite type Y and its thermal stability has been shown on the grounds of X-ray diffraction, differential thermal analysis, and infrared spectroscopic measurements.     

Structural and optical properties of Zn(Mg,Cd)O alloy films grown by remote-plasma-enhanced MOCVD

We report the structural and optical properties of wurtzite-structure Zn(Mg,Cd)O ternary alloys. Wurtzite (0 0 0 1) Zn_1−xCd_xO and Mg_yZn_1−yO films were grown on (11–20) sapphire substrates using remote-plasma-enhanced metalorganic chemical vapor deposition. The large bowing parameters of Zn_1−xCd_xO and Mg_yZn_1−yO ternary alloys are 3.0 and 3.5, respectively, which reflects the large difference of each binary’s electronegativity. We have analyzed the broadening of photoluminescence (PL) in Zn(Mg,Cd)O alloys on alloy content by taking into account the statistical alloy fluctuation and the localization of the exciton, and have clarified that the localization of the exciton strongly affects to PL full-width at half-maximum (FWHM) in Zn(Mg,Cd)O alloys. The alloy broadenings in steady-state PL of Zn(Mg,Cd)O alloys are in good agreement with the calculated tendency by the theoretical model based on the statistical alloy fluctuation, while PL FWHM of Zn_1−xCd_xO is three times larger than the calculated results. Moreover, as another way to confirm alloy broadening, we also have done time-resolved PL measurements and derived the localized depth of the exciton in ZnO-based system, indicating a good agreement with the tendency of PL FWHM broadening.     

Synthesis and structural characterization of 2-mercapto-1-tert-butylimidazole and its Group 12 metal derivatives (HmimtBu)2MBr2 (M = Zn, Cd, Hg)

2-Mercapto-1-tert-butylimidazole (Hmim^tBu) and its Group 12 metal complexes (Hmim^tBu)₂ MBr₂ (M = Zn, Cd, Hg) have been readily prepared and structurally characterized. Whereas the former displays a dimeric structure in the solid state with two S H–N interactions linking each pair of molecules, the four-coordinate complexes exhibit distorted tetrahedral geometries with the S–M–S angles in the range 103.2–135.2. The average M–Br bond lengths are 2.401, 2.567, and 2.688 Å for M = Zn, Cd, and Hg, respectively, and the corresponding average M–S bond distances are 2.350, 2.540, and 2.467 Å. The average C–S bond length for all the complexes (1.72 Å) is only ca. 0.02 Å longer than the corresponding value in the free ligand. Hmim^tBu is orthorhombic, space group Pbca, a = 10.1571(5) Å, b = 9.7906(5) Å, c = 17.6616(9) Å, V = 1756.34(15) ų, Z = 8; (Hmim^tBu)₂ZnBr₂ is monoclinic, space group C2/c, a = 17.187(3) Å, b = 8.9908(17) Å, c = 15.560(3) Å, = 117.206(3), V = 2138.3(7) ų, Z = 4; (Hmim^tBu)₂CdBr₂ is triclinic, space group P , a = 7.4625(6) Å, b = 9.6149(9) Å, c = 31.020(3) Å, = 93.485(2), = 94.579(2), = 103.872(2), V = 2146.6(3) ų, Z = 4; (Hmim^tBu)₂HgBr₂ is monoclinic, space group P2₁/c, a = 6.8908(6) Å, b = 10.2397(9) Å, c = 29.859(3) Å, = 94.364(2), V = 2100.7(3) ų, Z = 4.     

Surface preparation of AB semiconductors (Cd3As2, Zn3As2, Cd3P2, Zn3P2) under ultra-high vacuum conditions

The UHV surface preparation of AB materials (crystals and thin films) has been monitored with XPS and AES. Clean and stoichiometric surfaces of AB crystals were prepared by means of low energy ion bombardment and subsequent low temperature annealing. Stoichiometric Cd₃As₂ and Zn₃P₂ thin films with very low amounts of C and O were deposited by the evaporation of bulk material in the UHV. The quality of prepared AB crystal and thin film surfaces was sufficient to carry out density of states investigations (UPS, RELS) with success.     

Structural and thermal properties of some tellurite glasses

Tellurium oxide glasses were prepared by the hammer and anvil technique. The glass systems are (0.85TeO₂ + 0.15Z), where Z = K₂O, TiO₂, V₂O₅, MnO, Fe₂O₃, CoO, NiO or CuO. A second group is a ternary system 0.85TeO₂+(0.15 − x)TiO₂ + xFe₂O₃) with x=0.0, 0.05, 0.1, 0.15 mol. X-ray diffraction, infrared spectroscopy and differential thermal analysis measurements were carried out. The present study showed the different glass-forming groups, the glass transition and crystallization temperatures as well as the crystallization processes.     

Structural,morphological, ionic conductivity,and thermal properties of pectin-based polymer electrolytes

New polymer electrolytes (PEs), potentially interesting for solid-state electrochemical devices applications, were synthesized by a solvent casting method using pectin and ionic liquid (IL) N,N,N-trimethyl-N-(2-hydroxyethyl)ammonium bis(trifluoromethylsulfonyl)imide ([N_{1 1 1 2(OH)}] [NTf₂]. The resulting electrolytes besides being moderately homogenous and thermally stable below 155°C, they also exhibited good mechanical properties. The SPE membranes were analyzed by differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and complex impedance spectroscopy.     

Fe3+ doped SiO2 nanostructured gel-glasses: Structural,optical and magnetic properties

Transparent crack-free and bubble-free Fe³⁺ doped SiO₂ nanostructured gel-glasses were obtained by the sol–gel process. The process involves the hydrolysis and condensation of an appropriate molar ratio of tetraethoxysilane (TEOS), absolute ethanol, nitric acid and ferric nitrate, followed by stepwise annealing at temperatures ranging from 110 °C to 1000 °C. The structural variation of the gel-glasses and their influence on physical properties during annealing has been studied. It has been observed that monolithicity and chemical environment around Fe³⁺ in the gel-glasses are strongly dependent on the annealing temperatures. The colour of gel-glass samples is different for different annealing temperatures, mainly due to the different co-ordination state of Fe³⁺ and the generation of Fe₂O₃ colloids of size 20–60 nm in the silica matrix. The annealing process facilitates the tuning of the UV–visible transmission cut-off edge in high optical quality Fe³⁺ doped silica gel-glasses. A marked difference in the magnetic properties of these glasses is also observed with annealing temperatures.     

Thermal decomposition of partially Mg2+-exchanged forms of zeolite A investigated by DTA-and X-ray high temperature methods

Only the application of high temperature X-ray diffraction and DTA-methods results in an uncontradicted explanation of processes occuring at thermal decomposition of NaA-and Mg²⁺-exchanged zeolite in the temperature region of 700 to 1100°C. Decomposition of NaA-zeolite takes place depending on time and temperature in the following sequence: NaA-zeolite – amorphous phase – carnegieite – nepheline. Zeolites with degrees of exchange of magnesium ions above 50% on the other hand decompose at increasing temperature sucessively to the following phases: NaMgA-zeolite – amorphous phase – spinel, mullite and amorphous SiO₂.     

Cold rolling texture development in Zn,Cd and Mg

Studied are the regularities of preferred orientations in the process of rolling of zinc, magnesium, and cadmium. On the basis of the data obtained and analysis of crystallographic mechanism of Cd, Zn and Mg crystals a “dynamic” model of the rolling texture formation in zinc and cadmium as well as a “monotonic” one in magnesium are suggested.     

Influence of Zn2+ ions concentration on the optical properties of Zn/Er:LiNbO3 crystals

Congruent Er³⁺(3 mol%):LiNbO₃ crystals codoped with ZnO (X mol %, X=0, 3, 6 and 7) were grown by the Czochralski technique. The Er contents in the crystals were measured by an inductively coupled plasma atomic emission spectrometer (ICP‐AES). Under 800 nm excitation, the upconversion emission spectra reveal an enhancement of the green emission with respect to the red emission when the Zn²⁺ ions are introduced into Er:LiNbO₃ crystal. The effect of Zn²⁺ ions concentration on the intensity ratio of the green to red emission has been investigated. Two cross‐relaxation processes (²H_11/2 + ⁴I_13/2 → ⁴I_11/2 + ⁴F_9/2 and ⁴F_7/2 + ⁴I_11/2 → ⁴F_9/2 + ⁴F_9/2) are involved in populating the ⁴F_9/2 state, which bypass the green‐emitting states. The OH^‐ absorption spectra indicate that the Zn²⁺ codoping leads to a decreased concentration of Er³⁺ cluster sites contributing to the enhancement of the green emission. The studies on UV‐vis absorption spectra show that the heavily codoped with Zn²⁺ results in the reformation of the Er³⁺ cluster sites in Er:LiNbO₃. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structural and optical properties of CdO nanowires synthesized from Cd(OH)2 precursors by calcination

CdO nanowires were produced by calcination process using Cd(OH)₂nanowires as precursors. The Cd(OH)₂ nanowires were synthesized via arc discharge method submerged in de‐ionized water. Transmission electron microscopy (TEM) analysis of the as‐synthesized Cd(OH)₂ nanowires revealed that nanowire morphology was abundant form with the diameters range from 5 to 40 nm. In addition to the nanowire morphology, Cd(OH)₂ nanospheres and hexagonal shaped nanoparticles were also displayed. The Cd(OH)₂ nanostructures were used as precursors to produce CdO nanowires and calcinated in air at 400 °C for four hours. After calcination, the structural, morphological and optical properties of the as‐synthesized CdO nanowires were characterized by means of TEM, selected area electron diffraction (SAED), X‐ray diffraction (XRD) and UV‐vis spectroscopy. The XRD and SAED techniques showed that the as‐synthesized Cd(OH)₂ nanostructures could be transformed into CdO nanostructures after the calcination process. TEM results revealed that the as‐synthesized CdO nanowires were 5–30 nm in diameter and shorter than corresponding Cd(OH)₂ nanowires. In addition, the diameters of the spherical or irregular CdO nanoparticles ranged from 20 nm to 50 nm. UV‐vis spectroscopy analysis was showed that the direct gap of the CdO nanowires were found to be 2.60 eV which is slightly higher than the earlier reported values of the bulk CdO for direct band gaps (2.3 eV) due to quantum size effect. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Mixing properties of X–Pb, (X = Cd,In) liquid binary alloys

We study the mixing properties of Cd–Pb and In–Pb segregating alloy systems using the Quasi-chemical approximation model (QCAM) within the framework of Quasi-lattice theory (QLT). The energetics of mixing in liquid binary alloys has been analyzed through the study of the various thermodynamic quantities. Positive deviation from Raoultian behavior was observed in the mixing properties of the alloys calculated. Our results are in good agreement with reported experimental data and support a weak demixing tendency in both Cd–Pb and In–Pb liquid alloys.     

Structural and magnetic properties of nanometric Zn0.5Co0.5Fe2O4 prepared by hydrothermal method

ABSTRACT

The study of the structural, morphology and magnetic properties of Zn_0.5Co_0.5Fe₂O₄ ferrite is the objective of this work. The sample was prepared by hydrothermal method and was characterized by X-ray diffraction (XRD), (SEM) and (TEM) micrographs and magnetization measurements.

The magnetic hysteresis loops, field cooling (FC) and zero field cooling (ZFC) curves, in temperature range (0-400K), were measured using XL-SQUID magnetometer and the values of blocking temperatures (T_B) were determined. The results indicated that Zn_0.5Co_0.5Fe₂O₄ sample were formed in a single spinel phase and gives the value for the lattice parameter (8.3952 Å) and nanosizes of particles (13.8 nm) were compared with these obtained from ZnFe₂O₄ sample prepared also by synthesis method (8.4261 Å and 14 nm). Although, the superparamagnetic behaviour for Co-Zn ferrite has observed at 350K with a blocking temperature (T_B = 300K), that is maximum at the value obtained in the case of Zn-ferrite (T_B = 12K).     

Hg X n coordination polyhedra (X = F, Cl, Br, and I) in crystal structures

The crystallochemical analysis of 188 structures containing 252 crystallographic kinds of Hg(II) atoms in Hg X _n coordination polyhedra (X = F, Cl, Br, and I) has been performed by the method of intersecting spheres with the use of Vorono-Dirichlet polyhedra. It was found that halogen atoms surrounded by Hg(II) atoms are characterized by the coordination numbers from 3 to 8. It was demonstrated that, at the unvarying nature of the X atoms, the average Hg-X interatomic distance increases by 0.13–0.57 Å with an increase of the coordination number, whereas the average radius of spheres with the volume equal to that of the Vorono-Dirichlet polyhedron of a Hg atom is either independent of the coordination number (at X = F) or varies with it only by about 0.02–0.07 Å (at X = Cl, Br, and I). This allows the approximation of mercury atoms in the crystal structures by soft (deformable) spheres of a constant volume. Some results obtained in the analysis of the topology and the geometry of [Hg_m X _n ] ^z?-complexes in crystal structures are also presented.     

Optical and opto‐electronic properties of polycrystalline Cd0.96Zn0.04Te thin films

Cd_0.96Zn_0.04Te thin films are deposited onto thoroughly cleaned glass substrates (Corning 7059) kept at room temperature by vacuum evaporation. The films are found to have good stoichiometry as analyzed by Rutherford Backscattering Spectrometry. The films exhibited zinc blende structure with predominant (111) orientation. The surface morphology of the films is studied by Atomic Force Microscopy. The rms roughness of the films evaluated by AFM is 3.7 nm. The pseudodielectric‐function spectra, ε(E) = ε₁(E) + i ε₂(E) at room temperature are measured by spectroscopic ellipsometry. The measured dielectric function spectra reveal distinct structures at energies of the E₁, E₁+ Δ₁ and E₂ critical points. The band gap energy of the films measured by optical transmittance measurement is 1.523 eV. The PL spectrum of the films shows intense emission due to free and bound exciton recombination and no emission associated with crystal imperfection and deeper impurity levels. The PL line shapes give indications of the high quality of the layers.     

Structural and spectroscopic properties of 2-thiophenecarboxaldehyde 2-thienylhydrazone

In this paper the crystal and molecular structure of the title compound is reported. The crystals are monoclinic, P2₁/c,Z=4,a=13.406(4),b=5.367(1),c=15.545(6)Å,=110.00(5)°. The structure was solved by direct and Fourier methods and refined by full-matrix least squares toR=0.0497 andRw=0.0537 for 1094 unique reflections. The molecule shows an E-conflguration with respect to the C=N double bond. Mass and IR spectra are also discussed.     

Structural,thermal and optical studies on 2‐naphthol crystals

Single crystals of 2‐naphthol was grown in slow evaporation solution growth technique. Grown crystals were characterized by various characterization techniques. Powder X‐ ray diffraction studies reveal that the grown crystal belongs to monoclinic system with noncentrosymmetric space group. Vibrational bands of the various functional groups and their significance were investigated by analyzing the vibrational spectra. Melting point and the decomposition temperature of the grown crystal was premeditated from the thermal analysis. From the UV‐VIS‐NIR spectrum the electronic excitation mechanism and the transmittance abilities of the crystal was studied. Theoretical value of first static hyperpolarizability was calculated and compared with urea. Second harmonic generation efficiency of the crystal is 0.6 times that of KDP. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Cleavage of 2,2'-Dithiobis(pyridine N-oxide) in the Presence of Group 12 Metal Ions: Crystal Structures of [Hg2X2(pyrithionate)2] (X = Br,I) and Redetermination of [Zn2(pyrithionate)4]

Crystallography Reports - Reactions of 2,2'-dithiobis(pyridine N-oxide) with various ZnII metal precursors and HgII halides are investigated and the products structurally characterized by X-ray...     

Structural,electrical, thermal and optical properties of the nonlinear optical crystal L‐Arginine Fluoride

Single crystals of L‐Arginine Fluoride (LAF) have been grown by the slow evaporation technique, and the crystalline perfection was studied by HRXRD. Optical absorption studies reveal the lower cut off wavelength (280 nm) and the band gap (5.1 eV). The dielectric constant and dielectric loss have been measured as a function of frequency (42 Hz–5 MHz) and temperature (307‐368K) and the activation energy is 77 μeV. The thermal transport properties such as thermal conductivity (0.88 ± 0.02 W/mK) and specific heat capacity (482±24 J/kg/K) have been estimated by the photopyroelectric technique. The nonlinear refractive index n₂, is found to be of the order of 10⁻¹³ cm²/W by the Z‐scan technique.