Thermal,phase transition and FTIR spectroscopic studies in tetraethylammonium trichlorocadmiate crystals

Single crystals of tetraethylammonium trichlorocadmiate were grown by slow evaporation of aqueous solutions at room temperature. The bright and transparent crystals obtained were characterized through FTIR spectroscopy, thermo gravimetric (TG and DTA) and low temperature DSC analyses. A fitting decomposition pattern for the title compound was formulated based on the TG thermogram which shows a two‐stage weight loss between 300°C and 800°C. In this temperature range the DTA curve shows endothermic dips supporting the formulated decomposition pattern. The thermal anomalies observed in the low temperature DSC both during the heating and cooling cycles indicate the occurrence of the first and second order structural phase transitions in the compound. The FTIR and far IR spectra show characteristic vibration frequencies due to [N(C₂H₅)₄]⁺ and CdCl₃^‐ ions. Detailed structural analysis of the compound is under progress. (© 2005 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)     

Synthesis,characterization and structural phase transition studies in trismethylammonium pentachloro barium dihydrate single crystals

Single crystals of trismethylammonium pentachlorobarium dihydrate were grown by slow evaporation method at ambient temperature. The crystals were characterized through powder XRD, thermal, infrared and NMR spectral studies. While the powder XRD pattern confirms the crystallinity of the title compound, the TG indicates the removal of occluded and adsorbed water molecules from the crystal when it is heated up to 86 °C. The TG study also confirms the presence of two water molecules of crystallization which are dehydrated on heating the crystal between 107 °C and 150 °C. The anhydrous compound is found to be stable at least up to 900 °C. The DTA curve shows two endothermic dips corresponding to weight losses observed in the TG curve. The low temperature DSC study shows thermal anomalies during the heating and cooling cycles indicating both first and second order phase transitions. The high temperature DSC shows the stepwise dehydration indicating phase transitions at temperatures 103 °C and 145 °C. The characteristic vibrational frequencies due to methylammonium ion, BaCl₅ and other groups are assigned based on FTIR spectra. The NMR spectrum confirms the presence of protons of the methyl group and water of crystallization in the compound. In this paper, an attempt is also made to understand the effect of methyl group on the phase transitions of the compound in comparison with a closely related compound, trisammoniumpentachloro barium dihydrate. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis,spectral and thermal properties of non‐linear optical crystal ZnMg(SCN)4

Single crystals of zinc magnesium tetra thiocyanate [ZnMg(SCN)₄], a bimetallic thiocyanate complex, were grown by slow evaporation solution growth technique at room temperature. The bright, transparent and colourless crystals have well defined faces. The grown crystals were characterized through elemental analysis, powder X‐ray diffraction (XRD), thermogravimetric (TG) and differential thermal analysis (DTA), differential scanning calorimetric analysis (DSC), Fourier Transform Infra red (FTIR) and Optical studies. The elemental analysis confirms the stoichiometry of the synthesized crystals. The compound crystallizes under monoclinic structure with lattice parameters a = 10.055 Å, b = 7.44 Å, c = 6.00 Å and β = 90.113°. The TGA indicates 25 % weight loss at 205°C from which the decomposition pattern is formulated. The DSC study indicates that the crystal undergoes only first order phase transitions. The FTIR spectrum indicates among others the presence of metal‐nitrogen and metal‐sulphur bonds thus confirming the formation of the complex. The second harmonic‐generation (SHG) was confirmed by the emission of green radiation using Nd: YAG laser. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and characterization of (NH4)2CuBr2Cl2·2H2O crystals

Single crystals of a new compound, (NH₄)₂CuBr₂Cl₂.2H₂O, were grown from saturated aqueous solution at room temperature by slow evaporation method. The grown crystals were characterized through elemental, powder XRD, thermal and DSC analyses and FTIR and far IR spectra. The elemental analysis and the decomposition pattern formulated using the TG‐DTG studies confirm the stoichiometry of the compound. The crystallinity of the compound is confirmed from the powder XRD pattern. A preliminary single crystal X‐ray diffraction structural analysis reveals that the title compound belongs to the orthorhombic system with a = 7.7466 Å, b = 7.783 Å and c = 8.1211 Å. The low temperature DSC shows thermal anomalies at –161.1, –156.5, –152.4, –145.2, –134, –18.5, and 1.4°C during the heating run and at –4.3, –54.8, –66.1, –90.6, –109.7 and –147.2 °C during the cooling run. The thermal hysterses indicate first order phase transitions in the title compound at these temperatures. The FTIR spectra were used to assign the characteristic vibrational frequencies due to NH₄⁺, CuX₄^2– ions and other chemical bonds. The effect of substitution of two bromine atoms on the phase transitions of a closely related crystal, diammonium tetrachloro cuprate dihydrate is also discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

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)     

Synthesis and characterization of methylammonium tetrachlorocuprate (II) dihydrate crystals

Single crystals of methylammonium tetrachlorocuprate (II) dihydrate were obtained by slow evaporation method at room temperature. The crystals were characterized through powder XRD, thermogravimetric (TG‐DTA), low temperature DSC studies and FTIR and far IR spectra. While the powder XRD confirms the crystallinity of the compound, the TG and DTA studies confirm the formation of the compound in the stoichiometric ratio and the presence of two water molecules of crystallization. The low temperature DSC study indicates a thermal anomaly at ‐3°C. The ordering of CH₃NH₃ group at low temperature causes phase transitions in the compound. The IR spectra characterize the various chemical bonding and water molecules in the compound. Laser Raman spectral studies under progress would help understand the mechanism of phase transitions at low temperatures. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and thermal characterization of methylammonium tetrachloro zincate (II) monohydrate crystals

Single crystals of methylammonium tetrachloro zincate (II) monohydrate were grown by slow evaporation of saturated aqueous solutions at room temperature. The grown crystals were colourless, bright and transparent. The crystals were characterized through elemental analysis, powder X‐ray diffraction, thermogravimetric (TG‐DTA) and low temperature differential scanning calorimetric (DSC) techniques. While the powder XRD pattern shows the crystallinity of the compound, the elemental analysis and the TG‐DTA confirm the stoichiometry of the compound. The low temperature DSC indicates first order structural phase transition at ‐8°C during heating cycle. The FTIR and far IR spectra of the compound show characteristic vibrational frequencies due to CH₃NH₃ and ZnCl₄^2‐ ions and other chemical bonds. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and thermal,phase transition and FTIR spectral characterization of tetraethylammonium tetrachlorocuprate (II) crystals

Single crystals of tetraethylammonium tetrachlorocuprate (II), [N(C₂H₅)₄]₂CuCl₄, were grown by slow evaporation method at room temperature. The crystals were characterized through powder XRD, thermogravimetric (TG‐DTA), low temperature differential scanning calorimetric (DSC) studies and FTIR spectroscopy. While the powder XRD pattern of the compound shows sharp Bragg peaks confirming the crystallinity of the compound, the TG‐DTA studies confirm formation of the compound in the stoichiometric ratio. The thermal anomalies observed in DSC curve at ‐120°C in the heating cycle and around ‐30°C in the cooling cycle indicate a first order phase transition. The phase transition was predicted to be associated with the ordering of CuCl₄^2‐ and successive long range orientation of [N(C₂H₅)₄]⁺ ions which are disordered at high temperatures. The cationic [N(C₂H₅)₄]⁺ plays a role in phase transitions at low temperatures. The sharp exothermic peak observed in high temperature DSC indicates a structural phase transition when [N(C₂H₅)₄]CuCl₃ is formed on heating the compound. The FTIR spectra of the compound characterize the various chemical bonding and water molecules adsorbed in the compound. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Electical,Magnetic, and Thermal Properties of Cadmium Hydrogen Phosphate Hydrate Crystals

The d.c. electrical conductivity of pelletized samples of cadmium hydrogen phosphate hydrate (CHP) crystals have been studied in the temperature range 50 °C to 250 °C. It has been observed that CHP crystals exhibit ionic conductivity at 140 °C and possess semiconducting property. At room temperature CHP has stable crystal structure. From thermal analysis it is concluded that CHP crystals possess water of crystallization and the material to be diamagnetic.     

Growth and characterization of cadmium magnesium tetra thiocyanate crystals

Cadmium Magnesium Tetra Thiocyanate, CdMg(SCN)₄, [CMTC] belongs to bimetallic thiocyanate complexes. CMTC crystals has been grown by solution growth technique at room temperature. The morphologies of the grown crystals are identified by single crystal analysis. Also the Powder X‐ray Diffractogram of the crystal has been recorded and the various planes of reflection are identified. The title compound crystallizes under triclinic structure with lattice parameters a = 10.0976 Å, b = 7.5015 Å, c = 5.7720 Å and β = 90.2135°. The presence of magnesium and cadmium in the grown crystals were confirmed through Atomic Absorption Spectroscopy. The grown crystals are analysed qualitatively by Fourier Transform Infrared (FTIR) and Fourier Transform Raman spectral measurements. The transmittance spectrum of the crystal in the UV‐Visible region has been recorded and analysed. The dielectric measurements for the crystals were carried out in the microwave region. The thermal stabilities of the crystals were studied by using different thermal analyses like Thermo Gravimetric Analysis (TGA), Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC). (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Flux growth and characterizations of NdPO4 single crystals

Neodymium phosphate single crystals, NdPO₄, have been grown by a flux growth method using Li₂CO₃-2MoO₃ as a flux. The as-grown crystals were characterized by X-ray powder diffraction(XRPD), differential thermal analysis (DTA) and thermogravimetric analysis (TG) techniques. The results show that the as-grown crystals were well crystallized. The crystal was stable over the temperature range from 26 to 1200 °C in N₂. The specific heat of NdPO₄ crystal at room temperature was 0.41 J/g °C. The absorption and the fluorescence spectra of NdPO₄ crystal were also measured at room temperature.     

Synthesis,growth, morphology of the semiorganic nonlinear optical crystal L‐glutamic acid hydrochloride and its structural,thermal and SHG characterizations

One of the halide derivatives of L ‐glutamic acid which was identified as a semiorganic nonlinear optical material, L ‐glutamic acid hydrochloride [HOOC(CH₂)₂CH(NH₂)COOH.HCl], was grown as bulk single crystal and its significant properties were characterized. The stoichiometric title compound was synthesized and the solubility of its recrystallized form in DD water was determined in the temperature range 30–80 °C by gravimetric method. Structural confirmation was carried out by powder X ‐ray diffraction study through lattice parameter verification. Optical quality smaller dimension single crystals were grown from aqueous solution by self nucleation through slow evaporation of solvent method and a large dimension single crystal was grown by slow cooling method with reversible seed rotation technique. Morphological importances of different growth facets of the as grown crystals were studied through optical goniometry. Unit cell structure of the grown crystal was refined by single crystal X ‐ray diffraction analysis, functional groups present in the crystal responsible for various modes of vibrations were confirmed by FTIR spectroscopy analysis, thermal stability of the grown crytal was analysed by TG/DTA and DSC and second harmonic generation (SHG) of a fundamental Nd:YAG laser beam by Kurtz technique. Results indicate that the grown crystal is in stoichiometric composition and has significant improvement in its thermal and SHG properties when compared to pure L ‐glutamic acid polymorphs.     

Crystal growth of ZrW2O8 and its optical and mechanical characterization

ZrW₂O₈ is known for its isotropic negative thermal expansion over a wide of range of temperature from ?272 to 777 °C. However, ZrW₂O₈ melts incongruently at 1257 °C and is stable only over a short temperature interval between 1105 and 1257 °C. This makes the growth of single crystals a formidable challenge. In order to study the intrinsic properties of this compound, a repeatable, viable single crystal growth strategy is required. Here we report a simple, self-seeding, self-fluxing single crystal growth process which resulted in single crystals of ZrW₂O₈ up to about 4 mm in size. Grown crystals were characterized by X-ray diffraction (XRD), Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy. Mechanical properties of the crystals were studied using nanoindentation.     

Synthesis,thermal and IR spectral characterization of ammonium tetrabromocuprate (II) dihydrate crystals

Single crystals of a new compound, ammonium tetrabromocuprate (II) dihydrate were obtained by slow evaporation method. The crystals were characterized through thermogravimetric (TG), differential thermal analysis (DTA), low temperature differential scanning calorimetric (DSC) methods and infrared (IR) spectroscopic technique. While the TG study confirms the stoichiometry of the compound, the thermal hystereses in DSC indicate the occurrence of first order phase transitions in the compound at low temperatures. The FTIR spectrum of the compound characterizes the various chemical bond vibration frequencies. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis,Crystal Structure,and Characterization of 2-Phenyl-N-(pyrazin-2-yl)Acetamide

The title compound, 2-Phenyl-N-(pyrazin-2-yl)acetamide, C₁₂H₁₁N₃O, was prepared by the coupling reaction and the product was crystallized by using toluene and methanol mixture(1:1) The structure of the compound was confirmed by elemental analysis, FTIR, ¹H NMR, thermogravimetric analysis, differential thermal analysis, UV-Visible spectroscopy, and single-crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P 2₁/c with the following unit-cell parameters: a = 8.1614(10), b = 14.9430(13), c = 9.3877(9) Å, β = 103.653(12)°, and Z = 4. The crystal structure was solved by direct methods using single-crystal X-ray diffraction data collected at room temperature and refined by full-matrix least-squares procedures to a final R-value of 0.0465 for 1486 observed reflections. An intramolecular C&sbnd;H···O hydrogen bond generates an S(6) graph-set motif. In the crystal, molecules are linked by N&sbnd;H···O and C&sbnd;H···O hydrogen bonds, forming a two-dimensional network.     

The influence of metallic substitution on the physical properties of manganese mercury thiyocyanate crystals

Good optical grade single crystals of pure, Cd²⁺ and Mg²⁺ doped Manganese Mercury Thiyocyanate (MMTC) crystals are grown by slow solvent evaporation technique at room temperature. Single crystal XRD studies reveal that the incorporation of metallic dopants has not changed the structure of the parent crystal. The SHG efficiencies of the pure and doped samples of MMTC are measured by Kurtz Perry powder method and the results are compared with urea. It is evident from microhardness study that the presence of dopants has increased the mechanical strength of MMTC crystal. The TG/DTG studies confirm that the thermal decomposition temperatures of pure (353°C), Mg²⁺ doped (363°C) and Cd²⁺ doped (365°C) MMTC are relatively high when compared to other NLO crystals of the same family. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth,Morphology, Structure and Properties of Na3BaCl5 2H2O Crystals

Single crystals of Na₃BaCl₅ 2H₂O were obtained from saturated aqueous solutions at two different temperatures (27° C and 32° C). The crystal size increases with increasing temperature. The crystals obtained were subjected to a systematic morphological, X-ray and thermal analyses. The study of as-grown crystal morphology and surface morphology of Na₃BaCl₅ 2H₂O crystals clearly indicate the requirement of a slow rate of evaporation at temperatures 27 to 28° C, moderate supersaturation in order to obtain high quality single crystals of Na₃BaCl₅ 2H₂O. The X-ray diffraction studies give the following cell parameters for the title compound: monoclinic, P21/n, a = 8.5773(9), b = 9.5502(4), c = 5.2873(3) A, β =92.069°, V = 432.8 A³, Z = 2. The study of TGA curves indicate the occurrence of dehydration process at around 200° C and not the decomposition of the compound. Similarly, the low temperature DSC study indicates a thermal anomaly at 267 K, and the high temperature DSC study (323 K to 873 K) indicates the transition from dihydrate to monohydrate and in turn anhydrous state at 454.6 K for Na₃BaCl₅ 2H₂O crystals. Thus both the TGA and DSC curves conclude that the Na₃BaCl₅ 2H₂O crystals contain two molecules of water of crystallization and its molecular formula is Na₃BaCl₅ 2H₂O.     

Thermal and infrared studies of calcium malate crystals grown in diffusion limited medium

Single crystals of the title compound Ca (C₄H₅O₅)₂.10H₂O are grown in silica gel using controlled chemical reaction method. Multifaceted single crystals of size up to 8 × 4 × 2 mm³ are obtained. Powder X‐ray Diffraction (XRD) pattern of the grown crystal and the Fourier Transform Infra‐Red (FTIR) spectrum in the range 400–4000 cm^–1 are recorded. The vibrational bands corresponding to different functional groups are assigned. Thermal decomposition stages observed in the Thermo‐gravimetric (TG) and Differential Thermal Analysis (DTA) studies are discussed. A six‐stage thermal decomposition scheme is proposed for the compound. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and characterization of nonlinear optical zinc hydrogen phosphate single crystal grown in silica gel

Good optical quality single crystals of zinc hydrogen phosphate (ZnHPO₄) having dimensions up to 8×2×2 mm³ have been grown with the aid of sodium meta silicate gel. Single crystal XRD studies confirm that the crystal belongs to the orthorhombic system with space group P2₁2₁2₁. The functional groups present in the crystals were confirmed using FTIR technique. Optical absorbance shows very low absorption in the entire visible region. Differential thermal and thermo gravimetric analysis confirmed that the crystal is stable up to 193°C. Photoconductivity study reveals positive photoconductivity in the presence of photo active centers formed by trap energy levels. The NLO activity of the crystal was confirmed by Kurtz powder technique. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)