Growth and vibrational spectroscopic studies of pure and yttrium doped single crystals of trisodium barium pentachloride dihydrate

Single crystals of pure and rare earth doped trisodium barium pentachloride dihydrate have been grown by slow evaporation solution growth. The solubility of both pure and doped forms of Na3BaCl5 x 2H2O has been estimated. Vibrational spectra were recorded to determine the symmetries of molecular vibrations. The observed Raman and infrared bands were assigned and discussed in detail. The optical transparencies of the grown crystals were tested by UV-vis spectrophotometer.     

Growth, optical, mechanical and thermal studies of diglycine cadmium chloride single crystal

Transparent single crystals of diglycine cadmium chloride were grown by slow evaporation solution technique. To confirm the crystal structure, the grown crystals were subjected to single crystal as well as powder X-ray diffraction measurements and the structure was found to be monoclinic. The elemental analysis was carried out by energy dispersive X-ray spectroscopy. The crystalline perfection of the grown crystal was assessed by high-resolution X-ray diffractometry and found that the crystal quality is fairly good. The optical study reveals that the grown crystal is highly transparent in the region 250?C900?nm. Thermal studies reveal that the grown crystal is stable up to 245?°C. The michrohardness analysis revealed that the grown crystal belongs to soft material category. The high dielectric constant (>30) and low loss (<0.01) value also confirms that the grown crystal is a good candidate for device fabrications.     

Spectroscopic and optical studies on pure and doped single crystals of sulphate-mixed L-arginine phosphate monohydrate--a nonlinear optical crystal

Single crystals of pure and transition metal ions (Cu(2+) and VO(2+))-doped L-arginine sulpho phosphate monohydrate (sulphate-mixed L-arginine phosphate monohydrate, abbreviated as LASP) have been grown by solvent evaporation of the saturated aqueous solution at room temperature and characterized by single-crystal XRD, FT-IR, UV-Vis-NIR and EPR (single-crystal rotation) spectral studies. Kurtz powder technique shows an enhanced second harmonic generation (SHG) efficiency for LASP and its doped analogues than pure LAP. The EPR studies on LASP:VO(2+) reveal that the in-plane sigma-bonding is moderately covalent and the out-of-plane pi-bonding is highly covalent, which could be attributed to the cause of enhanced powder efficiency.     

Growth and vibrational spectra of doped KMgF3 single crystal

The different ions doped KMgF(3) single crystals are prepared by the vertical Bridgman method. The near-infrared absorption spectra for different parts of all as-growth crystals indicate that there is the best transparency in middle part. The correlation between the vibronic frequencies of Eu(2+) and the site displacement of Cu(+) co-doped ions is firstly studied, which indicates that Cu(+) ions replace the site of the Mg(2+) ions. The co-doped Eu(2+) counteracts the charge misfit causing by the replacement of Mg(2+) with Cu(+). The overlapping of the emission spectra of the Eu(2+) and the excitation spectra of the Cu(+) results in the energy transfer from Eu(2+) to Cu(+).     

Growth kinetics of barium sulphate suspensions

Growth rates of barium sulphate precipitates were followed by spectrophotometric transmission measurements. Interpretation of the results enabled the rate of precipitation to be characterized in terms of the surface area of precipitate and the concentration of reagents. Consistent rate constants were obtained which show that the rate of precipitation is not dependent upon which ion (barium or suphate) is in excess.     

Growth, thermal, and optical properties of l-asparagine monohydrate NLO single crystal

Single crystal of l-asparagine monohydrate (LAM), organic nonlinear optical material has been grown by slow evaporation solution growth technique. Single crystal X-ray diffraction analysis was employed to identify the cell parameters. FT-IR analysis was used to estimate the qualitative presence of the amino acids in the grown crystal. Anisotropy properties like thermal and dielectric properties were studied on the grown crystal. The sample was thermally stable up to 125 °C. Also various thermodynamic properties were calculated and reported for the first time. Optical properties such as optical absorption, second harmonic generation, photoluminescence and photoconductivity analysis were also studied on the grown crystal. Optical absorption studies showed a lower UV cut-off of 225 nm. The SHG efficiency of the sample was seven times higher than that of KDP. Photoluminescence study confirms the suitability of the material for the generation of blue radiation. Multilayer plate-like pattern of growth was observed by scanning electron microscopy. The photoconductivity study confirms that the LAM crystal has negative photoconducting nature.     

Electron paramagnetic resonance and optical studies of Cu2+ doped bis(thiourea)cadmium chloride single crystal

Electron paramagnetic resonance (EPR) and optical studies have been carried out on Cu²⁺ doped bis(thiourea)cadmium chloride single crystal, which belongs to a potential semi-organic non-linear material, at room temperature. The spin Hamiltonian parameters were determined as g_xx = 2.04331, g_yy = 2.04373, g_zz = 2.05750 and A_xx = 91G, A_yy = 115G, A_zz = 136G. These parameters suggest that the spectroscopic splitting parameter g and hyperfine splitting parameter A exhibit rhombic symmetry. The optical study reveals that the non-linear optical property of the host lattice has been enhanced due to Cu²⁺ doping.     

The kinetics of crystallization and dissolution of barium oxalate dihydrate and cadmium oxalate trihydrate

The kinetics of crystallization and dissolution of barium oxalate dihydrate and cadmium oxalate trihydrate have been studied at 25°C by following the changes in conductivity when supersaturated or subsaturated solutions are inoculated with seed crystals. In additive-free solutions, the growth of barium oxalate dihydrate seed crystals follows a rate law second order with respect to supersaturation, and a surface-controlled reaction is proposed. The same kinetic equation may be used to interpret the growth of this salt from supersaturated solutions containing a variety of phosphonate additives. However in these experiments the reaction is preceded by an initial fast surge in the concentration—time profiles. The rate of growth of cadmium oxalate trihydrate crystals varies linearly with supersaturation and this can be explained in terms of a surface diffusion model for growth. The dissolutions of both barium oxalate dihydrate and cadmium oxalate trihydrate follows a rate law in which the rate of reaction is proportional to the undersaturation and evidence is presented for a liquid transport rate-determining step for the dissolution reactions. Although both the crystallization and dissolution of cadmium oxalate trihydrate follow similar first order kinetic equations the appreciable differences in the values of the rate constants suggest that they are not reciprocal processes.     

Growth, structural, optical, thermal and mechanical properties of ammonium pentaborate single crystal

Nonlinear optical single crystals of ammonium pentaborate (APB) were grown by the slow cooling method from aqueous solution. Grown crystal was characterized by powder X-ray diffraction (PXRD) and FT-IR spectral analysis. Perfection of the grown crystal was evaluated by high-resolution X-ray diffractometry (HRXRD). The effect of nylon threading on the perfection of the grown bigger crystal was also studied by HRXRD. The range and percentage of optical transmission was ascertained by recording UV-vis-NIR spectrum. Thermal properties were investigated by TG-DTA and DSC analyses. Its mechanical hardness was estimated by Vickers microhardness tester.     

Effect of precompression on isothermal decomposition kinetics of pure and doped potassium bromate

Pure and doped samples of potassium bromate (KBrO₃) were subjected to precompression and their thermal decomposition kinetics was studied by thermogravimetry at 668 K. The samples decomposed in two stages governed by the same rate law (contracting square equation), but with different rate constants, k ₁ (for a α ≤ 0.45) and k ₂ (for α ≥ 0.45), as in the case of uncompressed samples. The rate constants k ₁ and k ₂ decreased dramatically on precompression, the decrease being higher for doped samples. Cation dopants (Ba²⁺, Al³⁺) caused more desensitization effect than the anion dopants ( \textSO₄ ^2- {\text{SO}}_{4}{}^{ 2- } , PO₄ ³⁻) of the same magnitude of charge and concentration. The results favor ionic diffusion mechanism proposed earlier on the basis of doping studies.     

Heat capacity of pure and doped V2O3 single crystals

Heat capacities have been measured for single crystals of V₂O₃, either pure or doped with 1 and 1.4 mole% Cr₂O₃ and Al₂O₃ over the temperature range 100–700°K. V₂O₃ undergoes a fairly sharp transition at low temperatures (～170°K) but fails to exhibit any thermal anomaly above 300°K. The thermal behavior of (M_xV_1?x)₂O₃, M = Cr, Al, is manifested by two transitions: one at low temperatures, 170–180°K for x = 0.01 and 180–190°K for x = 0.014, and the other at high temperatures. For x = 0.01, the high-temperature (HT) anomaly extended over the range 325–345°K (Cr-doped V₂O₃) and 345–365°K (Al-doped V₂O₃), respectively. The corresponding ranges for x = 0.014 were found to be 260–280°K and 270–290°K, respectively. Further, the HT anomaly was characterized by a large hysteresis (～50°K). The values of lattice heat capacity of pure and doped V₂O₃ were, however, found to be almost the same and could be empirically represented by the Debye (D)?Einstein (E) function $\text{D}\text{(}\text{580}\text{T}\text{) + 4}\text{E}\text{(}\text{θ}\text{T}\text{)}$ with θ values 430°K (T = 100–230°K) and 465°K (T > 230°K), respectively. Further, the enthalpy change ΔH associated with the HT anomaly in doped V₂O₃ (80 ≤ ΔH ≤ 510 J/mole) was 5–10 times smaller than the ΔH corresponding to the lower-temperature transition. The results cited here appear incompatible with the Mott transition model that has been invoked to explain the HT anomaly.     

Growth,vibrational, optical,thermal, magnetic and dielectric behavior of organo-metallic tetramethylammonium cadmium chloride crystal

Journal of Thermal Analysis and Calorimetry - Single crystals of tetramethylammonium cadmium chloride were grown by slow evaporation technique. The single-crystal X-ray diffraction revealed that...     

Growth,optical, thermal,dielectric and mechanical studies of sodium hydrogen succinate single crystal

Sodium hydrogen succinate, an alkali metallo-organic third-order nonlinear optical crystal, had been grown successfully using aqueous solution by slow evaporation technique at room temperature. Transparent single crystals were selected and subjected to single-crystal X-ray diffraction analysis to identify lattice parameters, space group and morphology. The grown crystal was further subjected to powder X-ray diffraction to analyze the crystalline quality, UV–Vis–NIR spectral analysis to reveal optical transparency, FTIR spectroscopy for confirmation of the functional group analysis and TG–DTG/DSC analysis to determine the thermal stability. The dielectric constant and dielectric loss were studied as a function of frequency at different temperatures, and the results were discussed. The mechanical properties were calculated by Vickers microhardness test, and the third-order nonlinear optical parameters such as nonlinear refractive index, nonlinear absorption coefficient and real and imaginary parts of the third-order nonlinear optical susceptibility were determined by Z-scan technique.     

Growth and characterization of glycine picrate single crystal

Glycine picrate (GP), an organic material, was synthesized and successfully grown by solution growth method. Cell parameters of the grown crystals were obtained from the single crystal X-ray diffraction analysis and the presence of functional groups was identified by FTIR study. Its optical properties were examined by UV-vis-NIR analysis, which shows that the crystal is transparent between the wavelengths 400 nm and 1000 nm. Thermal analysis carried out for the glycine picrate reveals that the crystal exhibits a single sharp weight loss at 214 degrees C. The fluorescence spectrum of glycine picrate was recorded. The Vicker's microhardness values were measured for the grown crystal.     

Growth and characterization of mercury cinnamate single crystal

Single crystals of mercury cinnamate were grown by slow evaporation of methanol solution at room temperature. The effect of mercury on the electronic structure of cinnamic acid was studied. The grown mercury cinnamate single crystals were characterized by UV, FTIR and TG-DTA. TG curve of mercury cinnamate exhibits higher thermal stability compared with cinnamic acid which was also confirmed by DTA curve. The spectroscopic studies give evidences of the distribution of the electronic charge in molecule, the delocalisation of π electrons and the reactivity of metal complexes. The Second harmonic generation efficiency is more pronounced in the presence of mercury dopant in the growth medium.     

Growth of ninhydrin single crystal and its characterization

A novel organic nonlinear optical crystal ninhydrin having good optical quality was grown by solution technique using aqua solution. The quality of the crystal was also examined by high-resolution X-ray diffraction study. Solubility studies were made at different temperatures. Functional groups present in the grown material were identified from the vibrational frequencies of recorded FTIR spectrum. Transmittance of the crystal was recorded using the UV-vis-NIR spectrophotometer. From the thermal analysis it was observed that the material exhibits single sharp melting point. The fluorescence spectrum of ninhydrin was recorded. The Vicker's microhardness values were measured for the grown crystal. Second harmonic generation conversion efficiency estimated using Kurtz and Perry method is about five times that of KDP.     

Spectral and thermal characterization of grown organic single crystal

The growth of semicarbazone of p-hydroxy benzaldehyde (SPHB) single crystal by slow evaporation solution growth technique is reported in this article. The grown crystal was subjected to powder XRD study to identify the crystalline nature. Single crystal XRD study was done to measure unit cell parameters and to confirm the crystal structure. In the presence of various functional groups of SPHB was identified by FTIR spectrum. Its optical behavior was examined by UV?CVis?CNIR spectrum and the crystal was found to have transparency in the region between 245 and 1100?nm. Thermal properties of the crystal were investigated using thermogravimetric and differential thermal analysis (TG-DTA), which indicated that the melting of the material occurred before decomposition. The nonlinear optical (NLO) property was tested by Kurtz?CPerry powder technique for second harmonic generations.     

Negative thermal expansion of a polydiacetylene single crystal

Macroscopic thermal expansion in the chain direction has been measured for the first time on organic polymeric single crystals. Negative linear thermal expansion coefficients αM are reported and related to chain torsional motion and equilibrium point-defect formation for a solid-state polymerized phase of 2,4-hexadiyne-1,6-diol bisphenylurethane (HDU) which contains crystallographically located interstitial dioxane and for a dioxanefree phase obtained by thermal annealing. Data for as-polymerized single crystals (which are probably of extended chain morphology) between ?50 and 100°C give αM = ?(1.686 ± 0.039) × 10^?5 ? (1.35 ± 0.18) × 10^?7 t with t in °C. During volatilization of 11.7 ± 1.0 wt-% interstitial dioxane and a resulting crystal structure change, the as-polymerized fibers fibrillate and shrink irreversibly by 0.16 ± 0.04%. Although dichroism and diffraction measurements indicate both a high degree of crystallinity and chain alignment for the dioxane-free phase, the average thermal expansion coefficient, (?3.0 ± 1.0) × 10^?6 °C^?1 between ?50 and 150°C, is about an order of magnitude less than for the as-polymerized single crystals.     

Radiolysis of quench-cooled pure and barium doped KNO3 in presence of oxides: Effect of particle size

Radiation decomposition studies of quenched pure KNO₃ and KNO₃ doped with Ba²⁺ ions in the presence of PbO or Al₂O₃ as a heterophase impurity showed that the yield of nitrite varied with the particle size of the nitrate. The G/NO ₂ ^– / values were also found to vary with the mol percent of PbO or Al₂O₃ in the mixture. Higher yields of nitrite were obtained in the presence of PbO, while in mixtures containing Al₂O₃, the yields of nitrite were lower in comparison with the G-values observed in the absence of oxide. These results are explained on the basis that a larger surface area results in an increased energy transfer at the interface between two neighbouring particles. The results can also be accounted for in terms of electron donor-acceptor properties of the added oxides.