Capsule‐like α‐Fe2O3 nanoparticles: Synthesis,characterization, and growth mechanism

Uniform capsule‐like α‐Fe₂O₃ particles were synthesized via a simple hydrothermal method, employing FeCl₃ and CH₃COONa as the precursors and sodium dodecyl sulfate (SDS) as soft template. X‐ray powder diffraction (XRD), field emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), and high‐resolution transmission electron microscopy were used to characterize the structure of synthesized products. Some factors influencing the formation of capsule‐like α‐Fe₂O₃ particles were systematically investigated, including different kinds of surfactants, the concentration of SDS, and reaction times. The investigation on the evolution formation reveals that SDS was critical to control the morphology of final products, and a possible five‐step growth mechanism was presented by tracking the structures of the products at different reaction stages.     

Growth of big single crystals of Sr2YRu1‐xCuxO6 from high temperature solutions

Single crystals of Sr₂YRu_1‐xCu_xO₆ (x = 0 ‐ 0.4) have been grown from PbO‐PbF₂ based solutions in the temperature range 1150 – 1350°C. A silicon carbide heating element furnace (with a recrystallized alumina tube lining) in a vertical configuration was used to grow the crystals in platinum crucibles. Conditions for the stable growth of big crystals have been investigated. The morphology of the crystals containing Cu was found to change from octahedral to cube octahedral as the growth temperature is increased from 1150 to 1350°C. Crystals measuring up to 4.5 mm across and 2.5 mm thick have been grown from 1250°C. The incorporation of Cu into the crystals was ascertained by EDS and x‐ray diffraction analysis. A diamagnetic transition which increased in magnitude and temperature with x was observed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal growth,morphology, spectrographic characterization and thermal properties of 4,5‐bis(benzoylthio)‐1,3‐dithiole‐2‐thione

Single crystals of 4,5‐bis(benzoylthio)‐1,3‐dithiole‐2‐thione (BBDT), were grown from methylene chloride and the growth morphology was deduced by the Bravais–Friedel Donnay–Harker (BFDH) model. The grown crystals were characterized by optical absorption, infrared, Raman and X‐ray powder diffraction spectroscopy. The thermal behavior of BBDT has been investigated by means of thermogravimetric analysis and differential thermal analysis measurements in air. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Thermal “order‐disorder” behaviour in (Na1‐xKx)4B8O14 solid solutions investigated by X‐ray powder diffraction

In the potassium‐rich part of the binary system Na₄B₈O₁₄‐K₄B₈O₁₄ solid solutions have been found that can be described with the formula (Na_1‐xK_x)₄B₈O₁₄ with 0.45 ≤ x < 1.0. The crystal structures of (Na_0.25K_0.75)₄B₈O₁₄ and (Na_0.45K_0.55)₄B₈O₁₄ were refined at room temperature by the Rietveld method. The solid solutions crystallize like K₄B₈O₁₄ in the triclinic crystal system, space group P ‐1, with K partially substituted for Na. An ordered distribution of the alkali atoms over the four cation sites at room temperature has been discovered. The structure of (Na_0.25K_0.75)₄B₈O₁₄ was also refined for data collected at 300 and 500 °C. The refinements show that sodium and potassium atoms are less ordered at higher temperatures. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

X‐ray studies on quaternary system RbXK1‐XBrYCl1‐Y

Single crystals of the quaternary crystalline solid solution system Rb_xK_1‐xBr_yCl_1‐y have been grown by melt technique for three different compositions y = 0.25, 0.50 and 0.75, keeping x = 0.5 and X‐ray diffraction studies have been carried out for each case independently, using spherically ground single crystals. The results indicate an enhancement of Debye‐Waller B(total) factors for the compositions y = 0.25 and 0.75 whereas for the intermediate composition, y = 0.5, the factor B(total) is close to the end member value. This experimental investigation show that for this composition, the crystalline solid solution behaves like an end member crystal.     

Temperature dependence of optical absorption in In1‐xGaxAs solid solutions

Absorption spectra near the fundamental absoption edge of n‐type of In_1‐xGa_xAs are studied. The temperature coefficient of the In_1‐xGa_xAs energy gap, dE_g/dT, has been obtained and compared with calculated data. An exponential dependence of the absorption coefficient on photon energy has been found. The slope of the exponential absorption curve is discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Czochralski growth of Lu1‐xScxBO3:Ce solid solution crystals

Single crystals of Lu_1‐xSc_xBO₃:Ce (x=0.2, 0.3, 0.5, 0.7) were grown by Czochralski method. Continuous solid solution with calcite structure and a linear compositional dependency of crystal lattice parameter in the system Lu_1‐xSc_xBO₃:Ce are formed and their symmetry belong to hexagonal system with R3c space group checked by X‐ray powder diffraction. The electron probe micro‐analysis measurements show that the main inclusions in Lu_1‐xSc_xBO₃:Ce crystals are in the form of Sc rich oxide and Ce rich oxide. The ICP‐AES tests show that the more Sc ion content in Lu_1‐xSc_xBO₃:Ce, the smaller effective segregation coefficient of Ce in crystal will be. The X‐ray excited luminescence spectra of Lu_1‐xSc_xBO₃:Ce crystals all present a double peaked emission band with maxima round 370 and 400 nm corresponding to Ce³⁺ emission and a self trapped excitons (STE) band peaking at 269 nm. In addition, due to high density, high relative light yield, fast decay time and no‐hygroscopic property, Lu_0.8Sc_0.2BO₃:1 at%Ce crystal could be a good candidate material for scintillation application by improving the crystal quality and cerium concentration. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Thermal expansion and structural properties of (CuAlTe2)1–x(CuAlSe2)x solid solutions

Investigations of the thermal expansion of (CuAlTe₂)_1–x(CuAlSe₂)_x solid solutions in the temperature range from 100 to 800 K have been carried out for the first time. It has been demonstrated that the thermal expansion coefficient α_L grows considerably in the temperature range from 100 to 300 K, whereas the temperature dependence above 300 K is rather weak. The isotherms of composition dependence of the thermal expansion coefficient α_L for 100, 293, 500 and 800 K were constructed, and it was found that linear relations could express them. The Debye temperatures θ_D , the average mean‐square dynamic displacements , the average root‐mean‐square amplitudes of thermal vibration RMS , the anion position parameter u using S. C. Abrahams & J. L. Bernstein (u_AB ) and J. E. Jaffe & A. Zunger (u_JZ ) models were calculated. The composition dependence of microhardness H using the phenomenological theory was also calculated, and it was discovered that this dependence has a non‐linear character with a maximum of 383 kg/mm² at x=0.67. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and characterization of 4‐(2‐hydroxyphenylamino)‐pent‐3‐en‐2‐one single crystals

4‐(2‐hydroxyphenylamino)‐pent‐3‐en‐2‐one (HPAP) was synthesized and single crystals were grown by the solution growth technique using methanol as a solvent. The crystals having orthorhombic symmetry were characterized by single crystal XRD, FTIR spectroscopy, NMR spectroscopy, TGA, DSC and dielectric studies. Very less variation in the value of dielectric constant is found for different frequencies of applied field. The crystals were exhibiting positive photoconductivity and poor NLO responses. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and characterization of 4,4′‐dihydroxy‐α‐methylstilbene crystal

4,4′‐dihydroxy‐α‐methylstilbene (DHAMS) was synthesized by condensation reaction with chloroacetone and phenol in the presence of concentrated sulfuric acid, and has been successfully grown by solution growth technique. This is the first report in the literature on the crystallization of DHAMS and exhibited the birefringent melt (liquid crystal property) of the optical properties. FTIR and FTNMR studies are in accordance with the structure. Good quality crystals were grown by slow evaporation technique by acetone as solvent. A transmission spectrum of the crystal was obtained in the region of 285 nm. The structural and optical properties were studied. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

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)     

Kinetic block model of crystal–mother‐phase interface with preferential clustering ‐ single layer case

A new single‐layer kinetic block model of crystal growth is proposed, which takes into account preference for bonds between blocks of the same type over mixed‐type bonds. The obtained parameters describing stable growth conditions were compared with other theoretical models (such as thermodynamic Jackson model and the earlier proposed kinetic model based on zeroth order approximation) which assume that new growth units are attached in a completely random way. Additionally, the results were compared with Monte Carlo simulations. The proposed model produced results which matched the simulation results much better than the other theoretical models. The new model can be used for studying crystal growth both from solution and from vapour. Calculations based on this model show that the number of created mixed‐type bonds depends on the temperature and is lower from its estimation obtained with the use of the zeroth order (Bragg‐Williams) approximation.     

The Crystal and Molecular Structure of tert‐Butoxycarbonyl ‐ α‐aminoisobutyryl ‐ isoleucyl ‐methylester

The crystal structure of the synthetic peptide Boc — Aib — Ile ‐ OMe (C₁₆ H₃ 0 N₂ O₅ ) has been determined from three‐dimensional X — ray diffraction data. The peptide crystallizes in triclinic space group P1 with a = 9.570(9), b = 10.261(7), c = 10.610(2) Å , α = 101.9(0), β = 91.7(0), γ = 98.6(0)° V = 1006.1(12) ų, Z = 2, D_calc = 1.09 Mg m^‐3. The structure was solved by direct methods and refined by full‐matrix least‐squares method to an R value of 0.072 (λ = 1.5418Å). The conformation of Aib residue in molecule A is αL and in molecule B is αR. The Ile residue in molecule A adopts folded conformation, while in molecule B it is in the extended region. The peptide units are trans and show significant deviations from planarity.     

Thermal analysis,powder diffraction and spectroscopic investigation of the solid phases of 1‐chloro‐2,2‐dimethylpropane

By the substitution of one methyl group in Neopentane C(CH₃)₄ with a methylchlorid group the globular sphere is expanded in 1‐chloro‐2,2‐dimethylpropane (CH₃)₃C(CH₂Cl). With the aid of DSC measurements, X‐ray powder diffraction, ¹H NMR and ³⁵Cl NQR measurements two orientationally disordered (plastic) phases were established. The low temperature structure was solved and a structural model of phase II is proposed. A mechanism to describe the reorientation in the different phases is given as well as a connectivity scheme between the phases is discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of Pb on the properties of Sr2YRu1‐xCuxO6 crystals grown from PbO‐PbF2 solutions at high temperatures

Single crystals of Sr₂YRu_1‐xCu_xO₆ with x=0 and x=0.1 were grown using PbO‐PbF₂ based solutions at different temperatures in the range 1150–1350°C. The influence of Pb from the solutions and the Cu from the solid solutions of Sr₂YRu_1‐xCu_xO₆ on the resulting crystals was studied using microstructure and magnetic property measurements. The peaks in the powder X‐ray diffraction patterns and Raman spectra do not change in the case of x=0 crystals but shift in the presence of Cu. A diamagnetic transition indicative of superconductivity was observed in the presence of Cu and an antiferromagnetic behavior with x=0. Based on these results it is concluded that Pb may not be incorporated in the crystals and even if it does the influence is not observed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Characterization and optical properties of ZnS nanorods branched out from ZnS film on Zn foil

Complex nanomaterial‐film‐metal substrate architectures, which are composed of ZnS nanorods, island‐like ZnS film and Zn foil, have been formed via a simple vapor deposition route. The growth of the complex nanostructures is initiated by the preferred formation of ZnS film, and ZnS nanorods branches out from ZnS film flows a liquid‐phase epitaxial growth mode. The ZnS nanorod is switched to an angle, which may be attributed to the sudden change of vapor pressure and temperature reduction by the end of vapor deposition process. The room‐temperature photoluminescence spectrum shows that complex ZnS nanostructures have a strong blue emission band centered at about 423 nm and a weak broad green emission band centered at about 515 nm. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal Structure Analysis of 1′,2′,3′,4′‐tetrahydro‐1,3‐diphenyl‐4‐chlorospiro[2‐pyrazoline‐5,2‐napthalen]1′one

The crystal structure of the title compound “1′,2′,3′,4′‐tetrahydro‐1,3‐diphenyl‐4‐chlorospiro[2‐pyrazoline‐5,2‐napthalen] 1′one” has been determined. The structure consists of a pyrazoline ring, three aromatic rings and a tetralone moiety. All the aromatic rings are planar while the cyclohexonone ring of the tetralone moiety is in the distorted sofa conformation. The molecular packing is stabilized by C‐H…O and C‐H…π type inter molecular interactions.     

The Setting Behaviour of α‐ and β‐CaSO4 · 0,5 H2O as a Function of Crystal Structure and Morphology

Calcium sulphate subhydrates (CaSO₄ · x H₂O, 0 < x ≤ 0.8) have a honeycomb‐shaped channel structure. The symmetry is either trigonal or a slight deviation thereof. Due to insufficient diffraction data and the high pseudosymmetry of the structure, it is not possible at this point to determine with certainty the specific arrangement of the water molecules in the channels. When the Fourier transformation method is used to calculate the growth form of the hemihydrate (x = 0.5), the calculated crystal form corresponds to the observed form only when the trigonal structural symmetry is largely retained. During dehydration of gypsum or, conversely, during the setting process of hemihydrate, heteroepitaxial growths of hemihydrate are observed on gypsum, or gypsum is grown heteroepitaxially on hemihydrate. The (100) faces of the hemihydrate and (010) of gypsum for the most part run parallel. Using diffraction and spectroscopic methods, it can be shown that a structural difference exists between α‐ and β‐hemihydrates, and that this difference probably accounts for the different setting behaviours. It is in this context that the presence of oxonium ions, particularly in β‐hemihydrate, found in NMR experiments is of interest. Textural studies indicated that the arrangement of gypsum crystals found in hardened gypsum is determined by the hemihydrate.     

Growth and characterization of 4‐Aminopyridinium‐4‐nitro phenolate single crystals

Organic optical material 4‐Aminopyridinium‐4‐nitro phenolate (4AP4NP) has been synthesized, and single crystals of size 20 x 14 x 6 mm³ have been grown from acetone solvent at room temperature by solvent evaporation technique. The grown crystals have been characterized by X‐ray diffraction to determine the cell parameters, and by FT‐IR technique to confirm the formation of the expected compound. The crystal belongs to monoclinic crystal system with space group P2₁/a.The structural perfection of the grown crystals has been analyzed by high‐resolution X‐ray diffraction (HRXRD) rocking curve measurements. The thermal stability of the compound has been determined by TG‐DTA curves. The transmittance of 4AP4NP has been used to determine the refractive index n; the extinction coefficient K and both the real ε_r and imaginary ε_i components of the dielectric constant as functions of photon energy. The optical band gap of 4AP4NP is 2.4 eV. The dielectric and mechanical behavior of the specimen was also studied. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Some structural considerations on the perovskite‐type A1‐ySryCo1‐xFexO3‐δ solid solution series

Solid solution series of La_1‐ySr_yCo_1‐xFe_xO_3‐δ were extensively studied in the past as cathode materials for solid oxide fuel cells. However, the crystal structure behavior of La_1‐ySr_yCo_1‐xFe_xO_3‐δ solid solution series when La‐ions are replaced with another rare‐earth ion or metallic alkaline earth metal is at present not fully understood. Here we report X‐ray powder diffraction measurements performed on samples of the Sm_0.8Sr_0.2Co_1‐xFe_xO_3‐δ solid solution series. This study demonstrates that the average A‐cation radius, as well as the Fe content (x), affects the structural modification of the A_1‐ySr_yCo_1‐xFe_xO_3+δ solid solution series significantly. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)