Flux growth and characterization of Ti‐ and Ni‐doped forsterite single crystals

Forsterite monocrystals doped with Ti and Ni were grown by the flux growth technique. A suitable mixture of flux (MoO₃, V₂O₅, Li₂CO₃) and nutrient was slowly cooled down to 750 °C from 1250 °C or 1350 °C. The crystals were then characterized by powder and single‐crystal X‐ray diffraction, scanning electron microscopy and differential scanning calorimetry (DSC). Variations observed in crystal size were attributed by both the varying experimental conditions in which they had been obtained, and to the amount of Ni substituted for Mg in the structure. High abundances of doped forsterite required a cooling rate of 1.8 K h^‐1. These synthetic, well‐characterized Ti and Ni doped forsterite crystals may have potential for exploitation in industrial fields. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal growth and structure of KBi(WO4)2 single crystals

Potassium bismuth tungstate [KBi(WO₄)₂] single crystals have been grown by the top‐seeded solution growth technique. Bulk crystal with dimensions up to several centimeters is obtained for the first time. Several self‐flux systems have been used for the growth from the solution and the experiments using K₂W₂O₇ as a solvent are detailed. Powder and single crystal X‐ray diffraction of this crystal are reported. The structure refinement shows that KBi(WO₄)₂ crystallizes in the monoclinic space group C2/c, with a=10.837(3), b=10.586(3), c=7.622(2)Å, β=130.860(3)°, V=661.4(3)ų, and Z=4. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth of ZnO single crystals by an induced nucleation from a high temperature solution of the ZnO‐PbF2 system

To grow ZnO single crystals from a high temperature solution of the ZnO‐PbF₂ system, a gas cooling system was assembled at the bottom of the crucible to induce nucleation in the initial growth stage. The growth experiments were carried out in a homemade vertical Bridgman furnace and Pt crucible of 28 mm in diameter was used. The furnace temperature was set to 1100°C and the flow rate of the oxygen gas was optimized as 3.0 l/min. ZnO crystal up to 5∼8mm in the thickness was obtained with the lowering rate of 0.3 mm/h. XRD patterns showed that the as‐grown crystal was pure ZnO Wurtzite phase. The impurity ions were analyzed by the glow discharge mass spectroscopy (GDMS) as 390.0 ppm and 40.0 ppm for Pb²⁺ and F^‐, respectively. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The effect of metallic ions on tapering phenomenon of DKDP crystals and its elimination

The anomalous wedge‐like shape of KH₂PO₄‐type single crystal, also called tapering, is discussed in this paper. DKDP single crystals grew on seeds from the solutions containing high concentrations of Al³⁺, Fe³⁺ and Cr³⁺ impurities. The tapering phenomenon occurred on the prismatic {010} faces, and the tapering angle θ was nearly measured as 10°. We adjusted the pD value of the solution from 3.0 to 4.2 by adding K₂CO₃, the tapering angle of DKDP crystal grown from the same solution at same supercooling was reduced to 0°. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structure and conformation of n‐ (t‐butoxycarbonyl)‐l‐valine‐l‐phenylalanine‐methyl ester (Boc‐Val‐Phe‐OMe)

The crystal structure of N‐ (t‐butoxycarbonyl) ‐ L‐valine‐L‐phenylalanine‐methyl ester (Boc‐Val‐Phe‐OMe), C₂₀H₃₀N₂O₅ was determined by X‐ray diffraction methods. The dipeptide crystallizes in orthorhombic space group P2₁2₁2₁, with cell parameters a = 5.0680(1) Å, b = 13.8650(1) Å and c = 28.2630(1) Å, V = 2143.8(5) ų, F.W. = 378.46, Z = 4, D_calc = 1.173 Mg/m³, μ = 0.687 mm^‐1, F₀₀₀ = 816, CuKα = 1.5418 Å. The structure was solved by direct methods and final R1 and wR2 are 0.0659 and 0.1654, respectively. The peptide unit is in trans conformation [ω = 177.4(9)°]. The conformation angles ϕ₁, ψ₁, ϕ₂ and ψ₂ for the peptide backbone are: ‐96.5(13)°, 101.2(13)°, ‐123.9(12)° and 34.0(15)°. The N‐H…O and C‐H…O hydrogen bondings influence the packing of the molecules in the dipeptide crystal. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Two organic‐inorganic hybrids with Keggin polyanions

Two new Keggin polyoxometalates [Co(phen)₃]₂[SiW₁₂O₄₀]·6H₂O (1) and (ppy)₆ H₄SiMo₁₂O₄₀·0.4H₂O (2) (phen = 1,10′‐phenanthroline, ppy = 4‐(5‐phenylpyridin‐2‐yl)pyridine) have been synthesized by the hydrothermal method. Single crystal X‐ray analysis revealed that compound 1 crystallizes in the monoclinic crystal system with cell parameters of a = 13.344(2) Å, b = 17.191(3) Å, c = 22.002(4) Å, α = 90.00°, β = 99.566(2)°, γ = 90.00°, V = 4977 ų, Z = 2, and compound 2 crystallizes in the triclinic crystal system with cell parameters of a = 11.297(2) Å, b = 12.341(3) Å, c = 19.354(4) Å, α = 107.60(3)°, β = 95.80(3)°, γ = 94.16(3)°, V = 2543.7(9) ų, Z = 1. Both 1 and 2 represent organic ligand molecules and inorganic Keggin anions, which are further interconnected to a 3D framework by supramolecular interactions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth behaviour of bulk GaN single crystals grown with various flux ratios using solvent‐thermal method

Bulk GaN single crystals were grown using a solvent‐thermal method. They were grown for 200 h at 600 °C and 800 °C using 8 MPa of N₂ gas and 1–3 mm sized pyramid GaN single crystals. Pure Na, NaN₃ and Ca were used as the flux. The mole fraction of the [flux]/([flux] + [Ga]) was 0.30–0.67. The growth behavior differed according to the flux ratio. The quality of the bulk GaN single crystals was improved by increasing the flux ratio. The bulk GaN single crystals formed by spontaneous nucleation were deposited on the BN crucible wall and bottom during the first step of synthesis. The wurtzite structure of the GaN grown single crystal was confirmed by x‐ray diffration. The chemical composition was analyzed by electron probe microanalysis. The quality and optical properties of the GaN single crystal were examined by Raman spectroscopy and photoluminesence analysis. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structure and electrochemical property of one‐dimensional complex: [K(cis‐syn‐cis‐ dicyclohexyl‐18‐crown‐6)]2[Cu(mnt)2]

One metalorganic complex [K(cis‐syn‐cis‐ dicyclohexyl‐18‐crown‐6)]₂[Cu(mnt)₂] (mnt = maleonitriledithiolate) has been obtained by the reaction of dicyclohexyl‐18‐crown‐6 with K₂mnt and CuCl₂·2H₂O. The title complex has been characterized by elementary analysis, FT‐IR, UV‐Vis spectroscopy and x‐ray single crystal diffraction. The title complex crystallizes in the triclinic space group P1 with crystallographic data: a = 10.870(6) Å, b = 11.536(6) Å, c = 12.904(7) Å, α = 101.541(10)°, β = 110.573(9)°, γ = 99.441(9)°, V = 1435.2(13) ų, Z = 1, D_calcd = 1.350 g/cm³, F(000) = 615, R₁ = 0.0641, wR₂ = 0.1475. It displays one‐dimensional chain‐like structure formed by [K(cis‐syn‐cis‐ dicyclohexyl‐18‐crown‐6)]⁺ complex cations and [Cu(mnt)₂]^2‐ complex anions through N‐K‐N interactions. Its electrochemical behavior has also been studied by the cyclic voltammetry. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Temperature‐concentration oscillations as a result of nanoheterophase structure of concentrated aqueous solutions of salts

Detailed precision investigation of aqueous solutions of NaBr·2H₂O, KBr, RbNO₃, and K₂SO₄ salts showed oscillations of crystal‐solution phase equilibria in the temperature range of 15–45 °C. The maximum deviations from the smooth correlation between the saturation temperature and the salt concentration (up to 4% of concentration and up to 10 °C) were found to correspond to simplest salt‐water ratios. Recently, similar trends were observed for NaNO₃, KNO₃ and K₂CrO₄ solutions. Oscillation amplitudes for saturation temperature in the investigated series decreased in the following orders: Na⁺→K⁺, Rb⁺, NH₄⁺ (nitrate systems), CrO₄^2–→SO₄^2– and Br^–→NO₃^– (potassium systems), and NO₃^–→Br^– (sodium systems). Increase in total content of impurities (2‐4‐fold) in solution results in 1.5‐2‐fold elevation of the oscillation amplitudes. A concept of nanoheterophase solution was suggested to account for the observed temperature‐concentration oscillations. The concept is based on the original experimental data on interrelated variation of different properties of aqueous salt solutions depending on their concentrations. Characteristic features of the phase diagrams are discussed and influence of the oscillations on crystal growth is elucidated. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structure and spectra character of cobalt nickel sulfate twelvehydrate (CNSH) single crystal

The title compound CoNi(SO₄)₂ · 12H₂O has been prepared and its crystal structure determined by single crystal X‐ray differaction at room temperature. The CNSH crystal structure belongs to the monoclinic space group C2/c,a = 9.966(2) Å, b = 7.2265(14) Å, c = 24.218(5) Å, β = 98.32(3)°, V = 1725.9(6) ų, z = 4, Dc = 2.024 gcm⁻³. The optical transmission character of CNSH crystal in aqueous solution is discontinuous in the range from ultraviolet to near IR wavelengths. The relationship between the structure and the optical transmission property is further discussed. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and characterization of magneto‐optical YFeO3 crystals

The floating zone growth of magneto‐optical crystal YFeO₃ has been investigated. The polycrystalline feed rod was prepared by a pressure of 250MPa and sintering at about 1500°C. A crack‐ free YFeO₃ single crystal has been successfully grown. The crystal preferred to crystallize along <100> direction with about 10° deviation. The X‐ray rocking curve of the crystal has a FWHM of 24 arcsec, confirming the high crystal quality of the sample. The (100) plane was etched by hot phosphoric acid and the dislocation density was about 10⁴/cm². A thin outer layer with Y₂O₃‐rich composition was found at the periphery of as‐grown crystals, which was attributed to the Fe₂O₃ evaporation during growth. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The Crystal and Molecular Structure of 11,12‐dibromo‐ 7,8—benzo‐1,5‐di(p—tolylsulphonyl)‐1,5‐diazacyclononan

The crystal structure of the title compound, C₂₅H₂₆Br₂N₂O₄S₂ was determined by single crystal X‐ray diffraction technique. The crystals are monoclinic, space group C 2/c, with a=20.7142(2) Å b=11.7910(2) Å, c= 10.6735(3) Å, β=98.549(2)°, V=2577.94(9) ų, Z=4. The structure was solved by direct methods and refined by least‐squares methods to a final R=0.046 for 1866 observed reflections with I>2sigma(I). The title compound, displays disordered geometry around the C1 atom located almost on twofold axis. The nine‐membered heterocylic ring is close to the half‐chair conformation. The dihedral angle between phenyl rings is 34.2(1)°.     

The influence of low-temperature annealings on the structural and superconducting properties of Bi 2212 and Bi 2201 whiskers

The influence of post-growth short-term low-temperature annealings (O₂, 400°C, 5–15 min) on the composition, crystal structure, and superconductivity of Bi₂Sr₂CaCu₂O_{8 + δ} and Bi₂Sr₂CuO_{6 + δ} oxycuprate whiskers freely grown in gas cavities has been investigated. The optimal conditions for growth in closed gas cavities in a flux and post-growth annealing in oxygen were found, making it possible to obtain high-quality superconducting Bi 2212 and Bi 2201 whiskers in a wide doping range (from heavily underdoped to optimally doped) with a small rocking curve half-width (～0.1^°–0.2^°) and narrow superconducting transition (ΔT = 1.5–2 K).     

The crystallisation of chromite-magnesiochromite spinels from a calcium magnesium aluminosilicate glass: Nucleation,crystal growth and final crystal sizes

The crystallisation of chromite-magnesiochromite spinels was studied from a calcium magnesium aluminosilicate glass (a simulated slag) containing 3 to 12 percent total iron oxides and 0.3 to 1.5 percent chromium(III) oxide, at temperatures from 1400° to 700 °C. – Spinel crystallisation occurred in glasses with 3–7 percent FeO and 0.7–1.1 percent Cr₂O₃. At temperatures 1100 °C and above, the nucleation was rapid and crystal numbers very high, at FeO contents above 3 percent and Cr₂O₃ contents above 0.7 percent; at 1056° and 1000 °C however, the crystal numbers reached some optimum values but then decreased as clinopyroxene crystals grew onto and enveloped the spinel microcrystals. In these glasses, the crystal lengths varied with growth time according to the relation, l_t = 2 k_g t^α = R_g1 t^α, where α = 0.7–1.0: this time dependence was a compromise between a relation for dendritic growth and one for facetted growth. The growth rates generally increased about five to seven times for 160 °C temperature rise: the energy of activation for the spinel crystal growth was then estimated as 180 ± 60 kJ mole⁻¹. – No spinel crystals were observed in glasses with more than 7 percent FeO content, only clinopyroxene crystals. Probably, these latter had nucleated rapidly and grown onto spinel microcrystals, while the spinel microcrystals were still of < 0.1 μm size.     

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)     

Growth and characterization of KBi(WO4)2 single crystals

Potassium bismuth tungstate [KBi(WO₄)₂] single crystals with dimensions up to 20 mm × 15 mm × 15 mm have been successfully grown by using the top‐seeded solution growth technique and K₂W₂O₇ as solvent. Experiments show that this crystal is unstable in a strong acid or alkali environment and has a blue fluorescence emission. The density, hardness, melting point, absorption edge, transparency range, prominent Raman shift frequency are 7.57 g/cm³, 238 kg/mm², 800 °C, 380 nm, 400–5450 nm, 868 cm^–1 respectively. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Single‐crystal growth and characterization of mullite‐type orthorhombic Bi2M4O9 (M = Al3+, Ga3+, Fe3+)

Pure and homogeneous single crystals of orthorhombic mullite‐type Bi₂M₄O₉ (M = Al³⁺, Ga³⁺, Fe³⁺), and a mixed Bi₂Fe_1.7Ga_2.3O₉ crystal from an equimolar Ga/Fe composition were grown by the top seeded solution growth (TSSG) method. All these compounds melt incongruently in the range of about 800 and 1100 °C. In case of bismuth gallate and ferrate inclusion‐free crystals with dimensions up to several cubic centimeters can be grown. Limited solubility in Bi₂O₃ and the high steepness of the liquidus curve are the reasons for getting only small imperfect bismuth aluminate crystals. In contrast to ceramic materials preparation reported in literature, divalent calcium and strontium could not be incorporated into the mullite‐type structure during the melt growth process. Several fundamental physical properties like heat capacity, thermal expansion, heat conductivity, elastic constants, high‐pressure behavior and oxygen diffusivity were determined by different research groups using single‐crystalline samples from the as‐grown materials. Furthermore, the refractive indices of Bi₂Ga₄O₉ were measured in the range of 0.430 and 0.700 μm. Such as many other bismuth containing compounds the refractive indices of Bi₂Ga₄O₉ are larger than 2, and Bi₂Ga₄O₉ is an optic biaxial positive crystal. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Solvothermal syntheses and crystal structures of two 4‐heterocyclic acylpyrazolone complexes

Many explorations of transition metal (M)‐L system under solvothermal condition, have led to the syntheses of two new 4‐heterocyclic acylpyrazolone complexes [Co(L)₂(CH₃OH)₂] (HL = 1‐phenyl‐3‐methyl‐4‐(2‐furoyl)‐5‐pyrazolone) ( 1 ) and [Cr(L)₃] ( 2 ). Single‐crystal X‐ray analyses reveal that crystal structures of compound 1 and 2 are respectively orthorhombic, Pbca, a = 15.0378(6) Å, b = 9.8405(4) Å, c = 20.7321(8) Å, V = 3067.9(2) ų, Z = 8 and triclinic, P‐1, a = 10.7966(18) Å, b = 13.023(2) Å, c = 15.520(3) Å, α = 73.011(4)°, β = 84.884(4)°, γ = 70.267(4)°, V = 1964.3(6) ų, Z = 2. Complex 1 has a two‐dimensional (2D) network structure that is formed by O–H···N H‐bonding interactions. Complex 2 makes a one‐dimensional (1D) zigzag chain structure by intermolecular π···π interactions, which is further interlinked via C–H···N H‐bonding interactions to generate a 2D sheet, and then a three‐dimensional (3D) supramolecular network structure is further linked by intermolecular C–H···π interactions. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal growth and spectral properties of Nd:Ca5(BO3)3F

A neodymium doped Ca₅(BO₃)₃F single crystal with size up to 51×48×8 mm³ has been grown by the top seeded solution growth (TSSG) technique with a Li₂O‐B₂O₃‐LiF flux. The spectra of absorption and fluorescence were measured at room temperature. According to Judd‐Ofelt (J‐O) theory, the spectroscopic parameters were calculated and the J‐O parameters Ω₂, Ω₄, Ω₆ were obtained as follows: Ω₂ = 1.41×10⁻²⁰cm², Ω₄ = 3.18×10⁻²⁰cm², Ω₆ = 2.11×10⁻²⁰cm². The room temperature fluorescence lifetime of NCBF was measured to be 51.8 μs. According to the J‐O paramenters, the emission probabilities of transitions, branching ratios, the radiative lifetime and the quantum efficiency from the Nd^{3+ 4}F_3/2 metastable state to lower lying J manifolds were also obtained. In comparasion with other Nd‐doped borate crystals, the calculated and experimental parameters show that NCBF is a promising SFD crystal.     

Synthesis,structural and thermal studies of tetrathioureacopper(I) chloride crystals

Tetrathioureacopper(I) chloride, hereafter abbreviated as TCC, was synthesised and single crystals were obtained from saturated aqueous solution by slow evaporation (solution growth) method at room temperature. The crystals obtained are bright, colourless and transparent having well defined external faces. The grown crystals were characterized through elemental analysis, single crystal X‐ray diffraction study, thermal analysis, electron spin resonance spectroscopy and Fourier Transform infrared spectroscopy. The elemental analysis confirms the stoichiometry of the compound. The single crystal diffraction studies indicate that TCC crystallises in the tetragonal lattice and the unit cell parameters are a = b = 13.4082 Å, c = 13.8074 Å, V = 2482.29 ų, α = β = γ = 90°. Space group and the number of molecules per unit cell (Z) are found to be P4₁2₁2 and 8 respectively. The TG curve of the sample shows a prolonged decomposition from 210 to 628.3 °C, from which the decomposition pattern has been formulated. The endothermic peaks in the DTA curve indicate melting and decomposition of the compound at 165.2 and 633.8 °C respectively. An exothermic peak in high temperature DSC indicates a phase transition in the compound at 274.8 °C. Thermal anomalies observed in the low temperature DSC at –163.3, –152.0, –141.5, –108.3, 1.0 and 12.1 °C in the heating run and –157.1 and –153.9 °C in the cooling run reveal first order phase transitions in the crystal. The peaks observed at –146.2 °C in both the heating and cooling runs suggest occurrence of a second order phase transition in this compound. The IR spectroscopic data were used to assign the characteristic vibrational frequencies of various groups present in the compound. The ESR study confirms that the copper is in the +1 oxidation state in the complex. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)