Effect of temperature and isomorphic atom substitution on optical absorption edge of TlInS2xSe2(1‐x) mixed crystals (0.25 ≤ x ≤ 1)

The optical properties of the TlInS_2xSe_2(1‐x)mixed crystals (0.25 ≤ x ≤ 1) have been investigated through the transmission and reflection measurements in the wavelength range of 400–1100 nm. The optical indirect band gap energies were determined by means of the analysis of the absorption data. It was found that the energy band gaps decrease with the increase of selenium atoms content in the TlInS_2xSe_2(1‐x)mixed crystals. The transmission measurements carried out in the temperature range of 10–300 K revealed that the rates of change of the indirect band gaps with temperature are γ = –9.2×10^–4 eV/K, –6.1×10^–4 eV/K, –4.7×10^–4 eV/K and –5.6×10^–4 eV/K for TlInS₂, TlInS_1.5Se_0.5, TlInSSe and TlInS_0.5Se_1.5 crystals, respectively. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth,structure, and superconducting properties of Bi2Sr2Ca2Cu3O10 and (Bi,Pb)2Sr2Ca2Cu3O10‐y crystals

Large and high‐quality single crystals of both Pb‐free and Pb‐doped high temperature superconducting compounds (Bi_1‐xPb_x)₂Sr₂Ca₂Cu₃O_10‐y (x = 0 and 0.3) were grown by means of a newly developed “Vapour‐Assisted Travelling Floating Zone” technique (VA‐TSFZ). This modified zone‐melting technique was realised in an image furnace and allowed for the first time to grow Pb‐doped crystals by compensating for the Pb losses occurring at high temperature. Crystals up to 3×2×0.1 mm³ were successfully grown. Post‐annealing under high pressure of O₂ (up to 10 MPa at T = 500°C) was undertaken to enhance T_c and improve the homogeneity of the crystals. Structural characterisation was performed by single‐crystal X‐ray diffraction (XRD) and the structure of the 3‐layer Bi‐based superconducting compound was refined for the first time. Structure refinement showed an incommensurate superlattice in the Pb‐free crystals. The space group is orthorhombic, A2aa, with cell parameters a = 27.105(4) Å, b = 5.4133(6) Å and c = 37.009(7) Å. Superconducting studies were carried out by A.C. and D.C. magnetic measurements. Very sharp superconducting transitions were obtained in both kinds of crystals (ΔT_c ≤ 1 K). In optimally doped Pb‐free crystals, critical temperatures up to 111 K were measured. Magnetic critical current densities of 2�10⁵ A/cm² were measured at T = 30 K and μ₀H = 0 T. A weak second peak in the magnetisation loops was observed in the temperature range 40‐50 K above which the vortex lattice becomes entangled. We have measured a portion of the irreversibility line (0.1‐5 Tesla) and fitted the expression for the melting of a vortex glass in a 2D fluctuation regime to the experimental data. Measurements of the lower critical field allowed to obtain the dependence of the penetration depth on temperature: the linear dependence of λ(T) for T < 30 K is consistent with d‐wave superconductivity in Bi‐2223. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Temperature‐tuned band gap energy and oscillator parameters of Tl2InGaSe4 semiconducting layered single crystals

The optical properties of Tl₂InGaSe₄ layered single crystals have been studied through the transmission and reflection measurements in the wavelength range of 500‐1100 nm. The analysis of room temperature absorption data revealed the presence of both optical indirect and direct transitions with band gap energies of 1.86 and 2.05 eV, respectively. Transmission measurements carried out in the temperature range of 10‐300 K revealed that the rate of change of the indirect band gap with temperature is γ = – 4.4 × 10^‐4 eV/K. The absolute zero value of the band gap energy was obtained as E_gi(0) = 1.95 eV. The dispersion of the refractive index is discussed in terms of the single oscillator model. The refractive index dispersion parameters: oscillator wavelength and strength were found to be 2.53 × 10^–7 m and 9.64 × 10¹³ m^–2, respectively. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Nonlinear optical properties of strontium tartrato‐antimonate(III) dihydrate,Sr[Sb2{(+)‐C4H2O6}2]·2H2O

The tensor of nonlinear optical susceptibility for second harmonic generation [d^SHG _ijk ] of hexagonal (point group 6) strontium tartrato‐antimonate(III) dihydrate, Sr[Sb₂{(+)‐C₄H₂O₆}₂]·2H₂O, was determined using the Maker fringes method and a Nd:YAG laser with a wavelength of 1064 nm. The largest component of the tensor d^SHG ₃₃₃ amounts two times d^SHG ₁₁₁ of α‐quartz. Effective nonlinear optical susceptibility d^SHG _eff is given for phase matching type I for several wavelengths (for type II d^SHG _eff is nearly zero). The thermal stability of crystals of Sr[Sb₂{(+)‐C₄H₂O₆}₂]·2H₂O was determined in the temperature range from 153 K to 573 K by means of thermal expansion measurements and thermogravimetry. The temperature dependence of thermal expansion coefficients is given in the range from 153 K to 293 K. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optical properties of non‐centrosymmetric mixed crystals K2(La1‐x Cex)(NO3)5 · 2 H2O (x = 0.0 – 1.0)

Large single crystals of optical quality of the non‐centrosymmetric orthorhombic potassium rare earth nitrate mixed crystals K₂(La_1–x Ce_x)(NO₃)₅ · 2 H₂O were grown at 38 °C from diluted HNO₃. For crystals with x = 0.0, 0.19, 0.38 and 0.66 refractive indices and their dispersion were determined with an error less than 1 · 10^–4 in the wavelength range 0.404 – 1.083 μm by the prism method. Phase matching conditions for collinear SHG frequency conversion were analysed in detail, including calculation of the effective nonlinear optical susceptibility. By an appropriate choice of the fraction x of cerium the mixed crystals K₂(La_1–x Ce_x)(NO₃)₅ · 2 H₂O allow an adjustment of non‐critical type I phase matching conditions to a desired wavelength of the fundamental wave within the range 1.055(4) – 1.107(6) μm. Non‐critical type II phase matching can be tuned in the wavelength range 0.949(2) – 0.931(2) μm. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

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)     

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)     

Crystal growth of zirconium‐doped KTiOPO4 crystals in the K2O‐P2O5‐TiO2‐ZrF4 system

Zirconium‐doped KTiOPO₄ (KTP) crystals were grown using a high temperature flux method in the K₂O‐P₂O₅‐TiO₂‐ZrF₄ system. The dopant content in the single crystals with general composition KTi_1‐xZr_xOPO₄ (where x = 0 – 0.026) strongly depends on zirconium concentration in the homogeneous melts. AES‐ICP method and X‐ray fluorescence analysis were used to determine the composition of the obtained crystals. Phase analyses of the products were performed using the powder XRD. The structures of KTiOPO₄ containing different quantities of Zr were refined on the basis of single crystal XRD data. Applying ZrF₄ precursor for zirconium injection into the flux allowed growing the zirconium‐doped KTP crystals at 930–750°C. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structure and optical properties of 4‐nitrophenyl 4‐butoxybenzoate

The title compound, C₁₇H₁₇N₁O₅, has been synthesized and characterized by single crystal X‐ray analysis and UV‐Vis spectra. The crystals are monoclinic, P 2₁/c, a = 17.994 (5) Å, b = 4.0592 (9) Å, c = 21.625 (5) Å, β = 99.634 (5)°, V = 1557.2 (6) ų and Z = 4. The molecule has an almost stretched form with a molecular length of 17.505 Å and an imbricated structure known for liquid crystals. The structure contains no direction‐specific intermolecular interactions like aromatic π‐π stacking and C‐H… π(arene) other than two weak C‐H…O hydrogen bonds. Good optical transmittance in the entire visible region of the UV‐Vis spectrum suggests that it is a potential candidate for optoelectronic applications. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

pH‐Controlled topologies of two Co(II) complexes based on 5‐Nitro‐1,2,3‐benzenetricarboxylic acid and 1,6‐Bis(1,2,4‐triazole‐1‐yl)hexane

Two new Co(II) coordination polymers, [Co(Hnbta)(bth)]_n ( 1 ) and {[Co₃(nbta)₂(bth)₃(H₂O)]·H₂O}_n ( 2 ), (H₃nbta = 5‐nitro‐1,2,3‐benzenetricarboxylic acid and bth = 1,6‐bis(1,2,4‐triazole‐1‐yl)hexane), have been synthesized under different pH values through hydrothermal reactions. Both complexes were characterized by elemental analysis, IR spectra, thermogravimetric analysis (TGA), and single‐crystal X‐ray crystallography. Complex 1 exhibits a 3D polythreaded network based on 4‐connected sql 2D layer. Complex 2 has a (4,4,5)‐connected trinodal 3D pillar‐layered network with a (4²·6⁴)₂(4²·6⁷·8)₂(6⁴·8²) topology. Magnetic susceptibility measurements indicate that complexes 1 and 2 show weak antiferromagnetic interactions between the adjacent Co(II) ions.     

Transport Properties of (NH4)2 CuCl4.2H2O Low Dimensional Single Crystals

The X‐ray diffraction and Infrared (IR) spectral studies of (NH₄)₂ CuCl₄.2H₂O single crystals reveals that these crystals contains tetragonal crystal structure with the unit cell dimensions of a = 7.58Å, c = 7.95Å, z= 2, β =90° and two water molecules in the unit cell. The temperature dependence of thermally stimulated depolarization current (TSDC) and dc electrical conductivity (σ) studies of this two‐dimensional (NH₄)₂ CuCl₄.2H₂O single crystal have been carried out in 77K–300K temperature region. The TSDC thermograph shows only one sharp peak at 248K with a peak current of 130nA, which is attributed to the Maxwell‐Wagner peak. The activation energy (U), relaxation time (τ) are calculated as 0.78eV and 3.44×10^‐15 s respectively. Dc electrical conductivity studies of these crystals show a first order phase transition at about 248K.     

Crystal structures and spectroscopic characterization of chiral and racemic 4‐phenyl‐1,3‐oxazolidin‐2‐one

Crystal structures of (R)‐ and (rac)‐4‐phenyl‐1,3‐oxazolidin‐2‐one (4‐POO) have been determined by X‐ray diffraction and characterized by the solid state ¹³C NMR and IR spectra. Molecular geometries and intermolecular interactions in (R)‐ and (rac)‐4‐POO crystals are very similar to each other; 4‐POO molecules are linked via the N‐H…O intermolecular hydrogen bonds to form the chained structure. Chemical shifts of the solid state ¹³C NMR spectra are very similar to each other, whereas the ¹H spin‐lattice relaxation times (T_1H) value for (R)‐4‐POO is five times as large as that for (rac)‐4‐POO, reflecting the more restricted mobility of the (R)‐4‐POO chain. Although both crystals contain an unique molecule in the asymmetric unit, a doublet feature is observed for the C=O stretching mode in the IR spectra of (R)‐ and (rac)‐4‐POO crystals. The frequency gap of the C=O bands are correlated with the strength of the dipole‐dipole interactions between the neighboring C=O groups. © 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Interaction in the molten system Rb2O‐P2O5‐TiO2‐NiO. Crystal structure of the langbeinite‐related Rb2Ni0.5Ti1.5(PO4)3

The interaction in the molten system Rb₂O‐P₂O₅‐TiO₂‐NiO was investigated at different molar ratios Rb/P = 0.5‐1.3, fixed Ti/P = 0.15, Ti/Ni = 1.0 at temperature range 1073–953 K. The conditions of formation of complex phosphates RbTi₂(PO₄)₃, Rb₂Ni_0.5Ti_1.5(PO₄)₃ and RbNiPO₄ have been determined. The new phosphate Rb₂Ni_0.5Ti_1.5(PO₄)₃ (space group P2₁3, a = 9.9386(2) Å) has been obtained and investigated by the single crystal X‐ray diffraction and FTIR‐spectroscopy. It has langbeinite‐like structure, that is built up from mixed (Ni/Ti)O₆‐octahedra and РО₄‐tetrahedra. Rubidium atoms are located in closed cavities of 3D‐framework.     

Growth and characterization of pure and Co2+‐doped Li2B4O7 single crystals

Pure and Co‐doped Li₂B₄O₇ (LBO) single crystals were grown by the Czochralski method. Starting concentrations of Co₂O₃ in the melt were: 0.5, 0.85 and 1 mol% relative to Li₂CO₃. Technological factors affecting the quality of both crystals were discussed. Optical absorption and EPR spectra were analyzed to define the oxidation states and lattice sites of cobalt ions. It was shown that Co²⁺ ions enter LBO crystal at octahedral Li⁺ site positions. Low‐temperature EPR measurements revealed that two types of Co²⁺ complexes can be distinguished in the Li₂B₄O₇:Co crystals. Additional absorption calculated for γ‐irradiated crystals showed V_k type defects suggesting the creation of cation vacancies during growth. The concentration of the defects decreases with an increase of intentional Co concentration. Introduction of cobalt ions to LBO crystal is limited probably by the formation of cobalt ion pairs or by the entrance of cobalt as Co⁺. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

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)     

Growth and spectroscopic investigation of Yb/Nd co‐doped KLu(WO4)2 laser crystals

Single crystals of Yb, Nd: KLu(WO₄)₂ (Yb, Nd: KLW) of dimensions up to 40mm× 40mm×5mm have been grown by top‐seeded solution growth (TSSG) method. X‐ray powder diffraction pattern was measured and compared with that of Nd: KLuW and Yb: KLuW. Absorption and fluorescence spectra were measured at room temperature. The Judd‐Ofelt theory was applied to analyze the spectrum of Nd, Yb: KLuW crystal. The intensity parameters Ω_t (t=2, 4 and 6) were calculated as Ω₂=20.68×10^‐20cm², Ω₄=11.04×10^‐20cm², Ω₆=6.74×10^‐20cm² respectively, with a root mean square deviation of 0.58×10^‐20 cm². (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Elastic and elasto‐optical properties of Rb1–x(NH4)xH2AsO4 mixed crystals studied by Brillouin spectroscopy

The elastic and elasto‐optical properties of Rb_1–x (NH₄)_x H₂AsO₄ mixed crystals were studied by Brillouin spectroscopy at room temperature. The measurements were made on single crystals obtained from the aqueous solution by slow evaporation. The behaviour of bulk phonons propagating in investigated crystals was studied for different polarisations of incident and scattered beam. The components of the tensors of elasto‐optical and elastic properties of the crystals studied were determined. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal data and some physical properties of Tl2InGaTe4 crystals

The room temperature crystal data, Debye temperature, dark and photoelectrical properties of the Bridgman method grown Tl₂InGaTe₄ crystals are reported for the first time. The X‐ray diffraction technique has revealed that Tl₂InGaTe₄ is a single phase crystal of tetragonal body‐centered structure belonging to the space group. A Debye temperature of 124 K is calculated from the results of the X‐ray data. The current‐voltage measurements have shown the existence of the switching property of the crystals at a critical voltage of 80 V. The dark electrical resistivity and Hall effect measurements indicated the n ‐type conduction with an electrical resistivity, electron density and Hall mobility of 2.49×10³ Ω cm, 4.76×10¹² cm^–3 and 527 cm²V^–1s^–1, respectively. The photosensitivity measurements on the crystal revealed that, the variation of photocurrent with illumination intensity is linear, indicating the domination of monomolecular recombination at room temperature. Moreover, the spectral distribution of the photocurrent allowed the determination of the energy band gap of the crystal studied as 0.88 eV. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Preparation,single crystal growth and characterization of bis(tetrabutylammonium)bis(4,5‐dithiolato‐1,3‐dithiole‐2‐thione)copper

The preparation and single crystal growth of bis(tetrabutylammonium)bis(4,5‐dithiolato‐1,3‐dithiole‐2‐thione)copper, (I), are described. The energy gap Eg of (I) is about 2.38 eV. The nonlinear optical susceptibility χ⁽³⁾ is about 1.3×10^‐3 esu at 1064 nm. The characterization of (I) has been performed by electronic absorption, infrared and X‐ray powder diffraction spectroscopy. The thermal behavior of (I) has been investigated by means of thermogravimetric analysis (TGA) and differential thermal analysis (DTA) measurements in air. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal Structure of Diethyl 2‐[2,2,2‐ trifluoro‐1‐(indole‐3‐yl)‐ethyl]‐2‐acetamidomalonate

The title compound (C₁₉H₂₁F₃N₂O₅) has been determined from three dimensional X‐ray diffraction data. The crystals are monoclinic, a = 7.626(4)Å, b = 17.515(4)Å, c = 15.066(3)Å, β = 101.02(3)°, V = 1975(1)ų, Z = 4, D_calc = 1.393g cm^‐3, space group P2₁/c. The structure was solved by direct methods and refined by full‐matrix least‐squares method (R = 0.039).