Preparation of Y3Al5O12 nanocrystals by low temperature glycol route

Yttrium aluminum garnet, Y₃Al₅O₁₂ (YAG) nanocrystals were synthesized by low temperature glycol method. This is a modified sol–gel method performed at low temperature that consists of a mixture of salts, mostly nitrates in an aqueous media. Single phase nanocrystalline YAG was obtained at 850°C, which is much lower than others such as wet‐chemical techniques. The structural characterization is done by XRD and transmission electron microscopy. The crystallite size range from 20‐50 nm was observed for the materials prepared at 850‐ 950°C. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Preparation of Nd:Y3Al5O12 nanocrystals by low temperature glycol route

Y₃Al₅O₁₂, yttrium aluminum garnet (YAG) single crystals are extensively used as host materials for solid‐state lasers. The materials in nano sizes are of immense importance due to their fascinating physical and chemical properties. Nanocrystals of Nd doped YAG were synthesized by low temperature glycol route. This method consists of a mixing of nitrates in an aqueous media at reasonably low temperatures. The Nd doping concentration was optimized and kept at 2 mol%. The prepared material was annealed at different temperatures. Single phase Nd:YAG nanocrystals were obtained at 850 °C. The prepared nanocrystals were characterized by XRD, SEM and TEM techniques for the crystalline phase, crystalline size and structure. The crystalline sizes were obtained in the range of ∼20–30 nm. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structural study on a new Cs2S2(SO4)3 crystal

A new type of dicesium disulfur trisulfate, Cs₂S₂(SO₄)₃, crystal has been crystallized. Differential scanning calorimetry (DSC) and X‐ray diffraction measurements have been performed on this compound. The crystal does not reveal any structural phase transition in the temperature range from 120 to 920 K. The compound belongs to a cubic system with space group P2₁3 at room temperature. It is found that both Cs and S atoms located on special positions are 93% occupied and 7% in exchange with each other. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis,structural and optical properties of well dispersed anatase TiO2 nanoparticles by non‐hydrothermal method

The formation of nanocrystalline TiO₂ particles has been investigated via a surfactant‐free synthetic non‐hydrothermal method. Titanium isopropoxide and toluene were used as the starting materials. At a low temperature of 250 °C for 6 h, the reaction mixture turned in to a white precipitate (TiO₂) as a result of the thermal decomposition of metal alkoxide. The obtained product was found to crystallize purely in the anatase phase with well defined morphology. The powder XRD study confirms that the average size of the particle is close to ∼15 nm. The TEM analysis indicates the sizes of the primary and secondary particles in the range between 8‐10 nm and 15‐20 nm respectively. The quantum size confinement of the crystallites is evident from the blue shift of the absorption edge in the UV‐Visible absorption spectrum. The luminescence property of the TiO₂ nanoparticles studied by the emission spectrum confirms the presence of defect levels caused by the oxygen vacancies. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structural investigation and electronic band transitions of nanostructured TiO2 thin films

Titanium dioxide (TiO₂) thin film was deposited on n‐Si (100) substrate by reactive DC magnetron sputtering system at 250 °C temperature. The deposited film was thermally treated for 3 h in the range of 400‐1000 °C by conventional thermal annealing (CTA) in air atmosphere. The effects of the annealing temperature on the structural and morphological properties of the films were investigated by X‐ray diffraction (XRD) and atomic force microscopy (AFM), respectively. XRD measurements show that the rutile phase is the dominant crystalline phase for the film annealed at 800 °C. According to AFM results, the increased grain sizes indicate that the annealing improves the crystalline quality of the TiO₂ film. In addition, the formation of the interfacial SiO₂ layer between TiO₂ film and Si substrate was evaluated by the transmittance spectra obtained with FTIR spectrometer. The electronic band transitions of as‐deposited and annealed films were also studied by using photoluminescence (PL) spectroscopy at room temperature. The results show that the dislocation density and microstrain in the film were decreased by increasing annealing temperature for both anatase and rutile phases. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

纳米GaN固体的制备与表征

本研究工作以氯化氨作矿化剂,在350～450℃、15～50MPa的条件下,用氨基钠作为氮的前体,和金属镓反应合成了氮化镓晶体.用X射线衍射、透射电子显微镜、激光拉曼光谱、红外光谱等方法对产物进行表征,结果显示得到的晶体为六方纤锌矿结构,平均粒径为16nm,晶格参数a=0.3215nm,c=0.5223nm.晶体的完整性好、产率高,并探讨了可能的反应机理.     

Structural study of the semimagnetic semiconductor Zn0.5Mn0.5In2Te4

The semimagnetic semiconductor alloy Zn_0.5Mn_0.5In₂Te₄ was refined from an X‐ray powder diffraction pattern using the Rietveld method. This compound crystallizes in the space group I42m (Nº 121), Z = 2, with unit cell parameters a = 6.1738(1) Å, c = 12.3572(4) Å, V = 471.00(2) Å3, c / a = 2.00. This material crystallizes in a stannite‐type structure. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structural and thermal characterization of L‐arginine dihydrate ‐ a nonlinear optical material

Crystal structure and thermal stability of the hydrated crystals of the basic amino acid L‐arginine named as L‐arginine dihydrate (LAD), a nonlinear optical material have been reported here. The title compound crystallized in the space group P2₁2₁2₁ with Z=4 and unit cell dimensions a=11.856(2)Å, b=15.694(2)Å, c=5.664(3)Å. The arginine molecule is a zwitterion with the guanidyl group accepting an extra proton from the carboxylate group. DTA‐TG analysis gives an idea about the thermal behaviour of LAD and ruled out the possibility of structural changes independent of mass changes. © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Complex crystallization mode of amorphous/nanocrystalline composite Al86Ni2Co5.8Gd5.7Si0.5

Kinetics of the first crystallization stage of Al₈₆Ni₂Co_5.8Gd_5.7Si_0.5 amorphous alloy and structure of the partially crystallized specimens were investigated by measurements of electrical resistance, X-ray diffraction and transmission electron microscopy. The presence of Al nanocrystals and eutectic colonies consisted of mutually oriented crystals of Al and metastable phase was found. The transient nucleation and slowing-down diffusion-limited growth and the interface-controlled growth of the quenched-in nuclei were identified as mechanisms of formation of the Al nanocrystals and eutectic colonies, respectively.     

Synthesis and characterization of inorganic‐organic ZnS(aminopropane)n composite materials

The main goal of our work was the synthesis and characterization of ZnS(aminopropane)_n hybrid inorganic‐organic layered materials. The basic material of our investigation was ZnS(1,3‐dap)_1/2, (where dap denotes diaminopropane). Its crystal structure has been solved by X‐ray powder diffraction methods. This layered compound was prepared using 1,3‐diaminepropane, zinc sulphate (ZnSO₄) and tioacetamide (CH₃CSNH₂). We have also tried to obtain and characterize other materials: ZnS(1‐ap) and ZnS(1,2‐dap), where ap denotes aminopropane. But in these last two cases diffraction patterns were of much poorer quality, which prevented a full structural survey; thus we cannot directly prove that hybrid lamellar materials were obtained. All compounds were studied using X‐ray diffraction, chemical analysis, UV‐vis spectroscopy and scanning electron microscopy. Additionally, using X‐ray diffraction as a function of temperature, we obtained information about structural changes of obtained composite materials under temperature treatment. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis,characterization and impedance spectroscopy of the new material [(CH3) (C6H5) 3P] 2CoBr4: a member of the A2BX4 family

The crystal structure of bis‐(methyltriphenylphosphonium) tetrabromocobaltate (II), [(C₁₉H₁₈P)₂ CoBr₄] is determined: M_r = 933.203, monoclinic, P2₁, a = 9. 6977 (3) Å, b = 12.5547 (4)Å, c = 16.4503 (6)Å, β = 105.603 (2)°, V = 1929.04 (11)ų, Z = 2, D_x = 1.607 Mg m^‐3, T = 298 K. Differential thermal analysis at high temperatures shows three endothermic peaks characterizing four phases, with onset temperatures at T₁= 313±2 K, T₂ = 320±4 K and T₃= 360±1 K. The structural instability detected via the temperature dependence of permittivity at T₁ is ascribed to order‐disorder transition associated with cation dipole reorientation. Permittivity and ac conductivity studies as a function of temperature (295 K‐375 K) and frequency (0.11 kHz < f <100 kHz) are presented. The results indicate the importance of the cation size and shape on the phase transitions in the system. Bulk conductivity behavior is thermally activated. The associated activation energies are in the range 2.9 to 1.0 eV depending on the temperature regime. Two contributions to the ac conductivity, one dominating at low temperatures and high frequencies which are characterized by superlinear frequency exponent and the second dominates at high temperatures characterized by a sublinear frequency exponent. The behavior is interpreted in terms of the jump relaxation model. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal Structure of pyridinium isopolymolybdate (C5H6N)2n[Mo4O13]n

Synthesis and crystal structure are described for pyridinium isopolymolybdate of chemical composition (C₅H₆N)_2n[Mo₄O₁₃]_n. The crystals are triclinic, space group P1, with the following unit‐cell parameters: a =8.2695(11) Å, b =10.544(4) Å, c =11.177(4) Å, α = 71.76(5)°, β = 89.68(3)°, γ = 78.79(3)°, V =906.4(4) ų, Z = 2 (chemical formula (C₅H₆N)₂[Mo₄O₁₃]), D _calcd = 2.755 g·cm^–3. Crystal structure was solved by Patterson methods and refined to a final R value 0.085 for 4045 independent reflections. The studied compound, considered in analogy to triclinic (NH₄)₂Mo₄O₁₃ as pyridinium polyoctamolybdate, is proposed to be better described as pyridinium isopolytetramolybdate (C₅H₆N)_2n[Mo₄O₁₃]_n. It seems that the proper coordination number of molybdenum (VI) ions is five, resulting in pyramidal coordination polyhedra [MoO₅]. Coordination polyhedra joined by common edges form tetramolybdate monomeric unit [Mo₄O₁₃]. The mers are connected by oxygen bridges Mo ‐ O ‐ Mo into infinite ribbon chains. Each two infinite chains are hold together by weaker intermolecular interactions. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structure and phase transition of single crystalline CsNH2SO3

Differential scanning calorimetry (DSC) and X‐ray diffraction measurements have been performed on cesium sulfamate CsNH₂SO₃ single crystal. Two distinct endothermic peaks in the DSC curves are observed at 330 and 436 K. It is pointed out that the peak at 330 K is attributed to the structural phase transition, and the other peak at 436 K is associated with the thermal decomposition of the crystal. The structures in room‐ and high‐temperasture phases are determined, and the space group of the sample crystal is found to change from monoclinic P 2₁/c to orthorhombic Pnma. The structure of the room‐temperature phase consists of two different types of N‐H···O hydrogen bond, but in the high‐temperature phase there is no specific hydrogen bond between the NSO₃ pseudo‐tetrahera. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and crystal structure of [CuCl(phen)2]3H3V10O28 · 7 H2O

The new compound, [CuCl(phen)₂]₃H₃V₁₀O₂₈ · 7 H₂O, was prepared by reaction of an aqueous KVO₃ solution (pH 3) with an aqueous solution of CuSO₄ · 5 H₂O in which 1,10‐phenanthroline (phen) and KCl were added. The crystal structure of the compound was determined, and the proton position in H₃V₁₀O₂₈^3– were calculated by the bond length/bond number method and also determined from difference electron density map. The protons are bound to colinearly arranged μ–OV₂ and μ–OV₃ groups which is the common protonation type in trihydrogen decavanadates. The structure crystallizes in P1 space group symmetry. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effects of annealing on structural,electrical and optical properties of AgGa(Se0.5S0.5)2 thin films deposited by using sintered stoichometric powder

The structural, electrical and optical properties of AgGa(Se_0.5S_0.5 )₂ thin films deposited by using the thermal evaporation method have been investigated as a function of annealing in the temperature range of 450–600 °C. X‐ray diffraction (XRD) analysis showed that the structural transformation from amorphous to polycrystalline structure started at 450 ^oC with mixed binary phases of Ga₂Se₃, Ga₂S₃, ternary phase of AgGaS₂ and single phase of S. The compositional analysis with the energy dispersive X‐ray analysis (EDXA) revealed that the as‐grown film has different elemental composition with the percentage values of Ag, Ga, Se and S being 5.58, 27.76, 13.84 and 52.82 % than the evaporation source powder, and the detailed information about the stoichometry and the segregation mechanisms of the constituent elements in the structure have been obtained. The optical band gap values as a function of annealing temperature were calculated as 2.68, 2.85, 2.82, 2.83, and 2.81 eV for as‐grown, annealed at 450, 500, 550, and 600 °C samples, respectively. It was determined that these changes in the band gap are related with the structural changes with annealing. The temperature dependent conductivity measurements were carried out in the temperature range of 250‐430 K for all samples. The room temperature resistivity value of as‐grown film was found to be 0.7x10⁸ (Ω‐cm) and reduced to 0.9x10⁷ (Ω‐cm) following to the annealing. From the variation of electrical conductivity as a function of the ambient temperature, the activation energies at specific temperature intervals for each sample were evaluated. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The Crystal Structure of the Cluster Complex [{Co(phen)2}2V4O12] · H2O

The crystal structure of [{Co(phen)₂}₂V₄O₁₂] · H₂O consists of hexanuclear bimetallic clusters [{Co(phen)₂}₂V₄O₁₂]. The cyclic [V₄O₁₂]^4‐ anion acts as a bidentate bridging ligand between the two [Co(phen)₂]²⁺ cations. The π‐π stacking interactions between the parallel 1,10‐phenantroline (phen) groups play a significant role in stabilizing this structure. The title compound crystallizes in the P2₁/c space group.     

Real Structure of LiB3O5 (LBO) Crystals Grown in Li2O‐B2O3‐MoO3 System

The liquidus surface structure and field of LiB₃O₅ (LBO) primary crystallization have been revealed in Li₂O‐B₂O₃ ‐MoO₃ ternary system. The optimization of charge composition and growth conditions results in large volume optical quality LBO single crystals yielding. Crystallographic properties and real defect structure of grown LBO single crystals have been investigated by X‐ray powder diffraction method and X‐ray reflection topography. The volume of the crystals is partly free of any structural imperfections.     

Crystal and molecular structure of 1‐allyl‐5‐(4‐methylbenzoyl)‐4‐(4‐methylphenyl)pyrimidine‐2(1H)‐thione

The crystal structure of 1‐allyl‐5‐(4‐methylbenzoyl)‐4‐(4‐methylphenyl)pyrimidine‐2(1H)‐thione (C₂₂H₂₀N₂OS) has been determined from three dimensional single crystal X‐ray diffraction data. The title compound crystallizes in the monoclinic space group P 2₁/c, with a = 10.6674(13), b = 10.1077(7), c = 17.9467(19) Å, β = 98.460(9)°, V = 1914.0(3) ų, D_calc = 1.251 g cm^–3, Z = 4. In the title compound, the allyl group shows positional disorder. Molecules are linked by C‐H···O, C‐H···N and C‐H···S intermolecular interactions forming two‐dimensional network. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and characterization of dihydroxylammonium tetrachlorocuprate dihydrate crystals

A new hydroxylammonium compound, [(NH₃OH)₂CuCl₄], was synthesized and its crystals were grown at room temperature by slow evaporation of aqueous solutions. The crystals were characterized through powder XRD, thermogravimetry (TG), differential thermal analysis (DTA), low temperature differential scanning calorimetric (DSC) and FTIR spectra. The X‐ray powder diffraction confirms the crystallinity of the compound. A fitting decomposition pattern of the compound was formulated based on the TG and thereby confirming the formation of the compound in the stoichiometric ratio. The thermal anomalies occurring in the low temperature DSC indicate successive phase transitions. The low temperature phase transitions are attributed to the ordering of [NH₃OH]⁺ ions. While most of the phase transitions are of first order type, the one occurring at –126 °C is of second order. Two glass transitions occur when the compound was cooled between –157.9 and –136.9 °C. The characteristic vibration bands due to [NH₃OH]⁺ and CuClequation/tex2gif-stack-1.gif ions are observed in the IR spectra. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Single crystal growth of CaMg2(SO4)3 via solid‐ / gas‐phase reactions and its Nasicon‐related crystal structure

Crystals of the double sulfate CaMg₂(SO₄)₃ have been obtained by solid‐state reactions of stoichiometric amounts of anhydrous CaSO₄ and MgSO₄ in sealed and evacuated silica tubes with chlorine gas as mineraliser. The crystal structure was determined from single crystal X‐ray diffractometer data [P 6₃/m, Z = 2, a = 8.3072(4), c = 7.3057(8) Å, R [F² > 2σ (F²)] = 0.0317, wR (F² all) = 0.0785, 476 structure factors, 33 variable parameters] and consists of distorted [CaO₆] octahedra (3 symmetry), [MgO₆] octahedra (3 symmetry) and SO₄ tetrahedra (m symmetry) as single building units. The structure is made up of ¹_∞[CaO_6/2] chains of face‐sharing [CaO₆] octahedra that extend parallel to [001], alternating with columns of face‐sharing [MgO_3/1O_3/2]₂ dimers. Both types of chains are linked via corner‐sharing with SO₄ tetrahedra into a three‐dimensional framework structure. Although the compound crystallizes in a new structure type, it is topologically related to the NaZr₂(PO₄)₃ (Nasicon) structure, and a comparative discussion between both structural arrangements is given. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)