Unidirectional growth of l-asparagine monohydrate single crystal: First time observation of NLO nature and other studies of crystalline perfection,optical, mechanical and dielectric properties

L-asparagine monohydrate (LAM), a new amino acid single crystal, was grown by slow evaporation solution technique (SEST) as well as by recently invented Sankaranarayanan–Ramasamy (SR) method in aqueous medium. Using SR method, LAM single crystal of diameter ∼18 mm and length ∼52 mm was grown for the first time. The growth conditions were optimized and the maximum growth rate of 1.0 mm per day was observed for the SR crystal. The crystal structure was confirmed by powder XRD. The crystalline perfection was assessed by high resolution XRD and etching studies and found that the quality of the SR crystal is better than the SEST crystal. The UV–vis–NIR spectroscopic study revealed that the SR crystal has good optical transparency than that of SEST crystal. The relative second harmonic generation efficiency was measured and found to be ∼0.35 times to that of KDP. The laser damage threshold (LDT) was measured and found that the SR crystal has higher LDT value (5.76 GW cm⁻²) than SEST crystal (4.75 GW cm⁻²). The Vickers’s microhardness and dielectric studies were also carried out and discussed.     

Synthesis,growth and characterization of organic nonlinear optical bis-glycine maleate (BGM) single crystals

A new organic compound of bis-glycine maleate was synthesized in the alkaline medium of 10% ammonium hydroxide solution. The bulk single crystals of Bis-Glycine Maleate (BGM) have been grown by slow cooling method. The grown crystals were characterized by employing single crystal and powder X-ray diffraction, Fourier transform infrared, optical absorption spectral studies and thermo gravimetric analysis. The microhardness studies confirmed that the BGM has a fairly high Vicker’s hardness number value (41 kg mm⁻²) in comparison to other organic NLO crystals. Second harmonic generation efficiency of the crystal measured by Kurtz–Perry powder method using Nd:YAG laser is found to be comparable to that of potassium dihydrogen phosphate (KDP). Frequency dependent dielectric studies were carried out along the major growth axis.     

Growth and characterization of organic material 4-nitrobenzaldehyde single crystal using modified vertical Bridgman technique

The organic material 4-nitrobenzaldehyde single crystal has been grown using the single wall ampoule with nano-translation by modified vertical Bridgman technique. The grown crystal was confirmed by single and powder X-ray diffraction (XRD). Fourier transform infrared (FTIR) analysis was used to identify the functional groups present in the grown crystal. The optical property of the grown crystal was analyzed by UV–vis–NIR and photoluminescence (PL) spectral measurements. The thermal characteristics of the grown crystal were analyzed by thermogravimetric (TG) and differential thermal analyses (DTA). The dielectric measurements were carried out with four different frequencies and the results indicate an increase in dielectric and conductivity parameters with the increase of temperature at all frequencies. The microhardness measurements were used to analyze the mechanical property of the grown crystal.     

Synthesis, growth of organic nonlinear optical crystal: Semicarbazone of 2-amino-5-chloro-benzophenone (S2A5CB) and its characterisation

A new organic crystal of semicarbazone of 2–amino–5–chloro–benzophenone has been grown as a single crystal by slow evaporation solution growth technique for the first time in the literature. The grown crystal has been characterised by proton nuclear magnetic resonance spectral analysis and single crystal and powder X-ray diffraction studies. Functional groups of the crystallised molecules were confirmed by FT-IR and FT-Raman analyses. Mechanical strength of the crystals was studied by microhardness test. Optical transparency of the grown crystals has been studied by UV-Visible spectra. The second harmonic generation property of the compound was analysed.     

Growth and optical properties of self-frequency-doubling laser crystal Yb:LuAl3(BO3)4

Single crystal of Yb:LuAl₃(BO₃)₄(Yb:LuAB) was grown by the flux method for the first time. The cell parameters of the grown crystal were estimated by X-ray diffraction analysis. The result indicates the symmetry of trigonal space group R32, with lattice parameters a=b=9.26372 Å, c=7.21405 Å, V=536.14 Å³, and Z=4. The absorption and emission spectra of Yb:LuAB crystal at room temperature has also been studied. The fluorescence lifetime for Yb:LuAB crystal is about 1.48 ms. The heat capacity was measured from 25 to 500 °C. Its second harmonic generation efficiency in LuAl₃(BO₃)₄ crystal is 3–4 times that of KDP crystal. These results show that Yb:LuAB crystal would be a potential self-frequency-doubling laser crystal.     

Growth and characterisation of benzaldehyde semicarbazone (BSC) single crystals

Single crystals of potential organic nonlinear optical materials of Benzaldehyde Semicarbazone (BSC) were grown by slow evaporation technique. The grown crystals were identified by X-ray diffraction method. The functional groups were identified from FT-IR spectrum. UV-visible and thermal gravimetric analyses were made.     

Preparation,crystal structure,spectrographic characterization,thermal and third order nonlinear optical properties of benzyltriethylamine bis(2-thioxo-1,3-dithiole-4,5-dithiolato)nickel(III)

The preparation and crystal structure of a novel nonlinear optical organometallic crystal, benzyltriethylamine bis(2-thioxo-1,3-dithiole-4,5-dithiolato)nickel(III) (BTEANDT), are described. The crystal was characterized by elemental analyses, infrared and X-ray powder diffraction spectroscopy, thermal analysis and optical absorption. The third order nonlinear optical properties of crystal were investigated by using the Z-scan technique at 1064 nm with 20 ps. A self-focusing effect and a saturable absorption were observed. The nonlinear refraction coefficient (n₂) and the nonlinear absorption coefficient (β) have been found to be 7.311×10⁻¹⁸ m²/W and −6.064×10⁻¹¹ m/W when the on-axis irradiance at focus (I₀) is 3.025 GW/cm². The relationship between β and I₀ was studied, which has revealed that the former is proportional to the latter. The result has been explained with the theory of absorption cross-section.     

Gel growth of α and γ glycine and their characterization

The microbial free single crystals of α and γ glycine were grown from gel at room temperature in a new chemical route. These crystals showed a superior quality than the solution grown crystals. The metastable α-form and the stable γ-form of glycine were crystallized in silica gel by solubility reduction method. The form of crystallization is confirmed by single crystal and powder X-ray diffraction analyses. The crystals of α and γ glycine were found to crystallize in monoclinic and hexagonal crystal systems, respectively. For analyzing the functional group and thermal stability of α and γ glycine crystals, spectroscopic and thermal analyses have been carried out. The dielectric studies were performed to find the dielectric constant of the grown crystals and the results are discussed. Second harmonic generation efficiency of the crystal was measured by Kurtz’s powder method using Nd:YAG laser and it was found to be 2.68 times that of potassium dihydrogen phosphate crystals.     

Growth and Raman spectroscopic characterization of As4S4 (II) single crystals

As described by Kutoglu (1976 [16]), single crystals of As₄S₄ (II) phase have been grown using a new two-step synthesis that drastically increases the reproducibility that is attainable in synthetic experiments. First, through photo-induced phase transformation, pararealgar powder is prepared as a precursor instead of AsS melt. Then it is dissolved and recrystallized from CS₂ solvent. Results show that single crystals of the As₄S₄ (II) phase were obtained reproducibly through the dissolution–recrystallization process. Single crystals of As₄S₄ (II) obtained using this method were translucent and showed a uniform yellow-orange color. The crystal exhibits a platelet-like shape as a thin film with well-developed faces (0 1 0) and (0 1¯ 0). The grown crystals are as large as 0.50×0.50×0.01 mm. They were characterized using powder and single crystal X-ray diffraction techniques to confirm the phase identification and the lattice parameters. The As₄S₄ (II) phase crystallizes in monoclinic system with cell parameters a=11.202(4) Å, b=9.954(4) Å, c=7.142(4) Å, β=92.81(4)°, V=795.4(6) Å³, which shows good agreement with the former value. Raman spectroscopic studies elucidated the behavior of the substance and the relation among phases of tetra-arsenic tetrasulfide.     

Unidirectional seeded single crystal growth from solution of benzophenone

A novel crystal growth method has been established for the growth of single crystal with selective orientation at room temperature. Using volatile solvent, the saturated solution containing the material to be crystallized was taken in an ampoule and allowed to crystallize by slow solvent evaporation assisted with a ring heater. The orientation of the growing crystal was imposed by means of a seed fixed at the bottom of the ampoule. By selecting a suitable ring heater voltage and by controlling the ring heater voltage, nucleation and the growth rate of the crystal were controlled more effectively. By employing this novel method, benzophenone single crystal ingots of diameters 10 and 20 mm and length more than 50 mm were successfully grown using xylene as solvent. The ease in scaling up of diameter from 10 to 20 mm shows the vital advantage of this technique. It was possible to achieve solute–crystal conversion efficiency of 100 percent. The grown benzophenone crystal was characterized by FTIR, TG and DTA, powder X-ray diffraction, X-ray rocking curve, optical transmission study and powder SHG measurement. The results show that the crystal quality is at least as good as the quality of the crystal grown by other known methods. Also, microbial growth was naturally avoided in this method, as the fresh solution is constantly made available for the growing crystal.     

Large-size β-Ga2O3 single crystals and wafers

Large-size single crystals of β-Ga₂O₃ with 1 inc in diameter have been grown by the floating zone technique. The stable growth conditions have been determined by the examination of the crystal structure. Wafers have been cut and fine polished in the (1 0 0), (0 1 0) and (0 0 1) planes. These were highly transparent in the visible and near UV, as well as electrically conductive, indicating the potential use of β-Ga₂O₃ as a substrate for optoelectic devices operating in the visible/near UV and with vertical current flow.     

Solution growth of single crystals of 4-hydroxycyanobenzene (4HCB) suitable for electronic applications

Squared, platelet-like single crystals of 4-hydroxycyanobenzene (4HCB) have been grown from solutions based on ethylic ether and petroleum ether. Properly modifying the growth conditions, in terms of both solvent used for the growth and concentration of 4HCB in the starting solution, allowed one to tune the planar dimensions of the platelets in the range 2–6 mm, and their thickness in the range 150–600 μm. In this way samples well suited for desired practical manipulation and electronic measurements may be obtained. Moreover, lowering the growth temperature resulted in larger but still thin 4HCB crystals. The ability to tailor crystal thickness has allowed one to study their Space-Charge Limited Current (SCLC) behaviour along that dimension, showing that the so-contacted samples exhibit intrinsic-like bulk conduction behaviour, and are hence well suitable for electronic studies and applications.     

Synthesis, growth, thermal, optical, dielectric and mechanical properties of semi-organic NLO crystal: Potassium hydrogen malate monohydrate

Potassium hydrogen malate monohydrate (PHMM), a semi-organic nonlinear optical material, has been synthesized and single crystals were grown from aqueous solution. Single crystals of PHMM have been grown by slow evaporation of solvent at room temperature up to dimensions of 22 mm×16 mm×14 mm. Single-crystal X-ray diffraction study on grown crystals shows that they belong to monoclinic system and non-centrosymmetry spacegroup Cc. The structural perfection of the grown crystals has been analyzed by high-resolution X-ray diffraction (HRXRD) rocking curve measurements. Fourier transform infrared (FTIR) spectroscopic study was performed for the identification of different modes of functional groups present in the compound. The UV–Vis transmission spectrum has been recorded in the range 200–1100 nm. The thermal stability of the compound has been determined by TG-DTA curves. The dielectric studies were performed. From the microhardness measurements, Vicker's hardness number (H_v), Stiffness constant (C₁₁), fracture toughness (k_c), Brittle index (B_i) and yield strength (σ_y) have been calculated. The Young's modulus was calculated using the Knoop hardness measurement. The SHG relative efficiency of PHMM crystal was found to be 1.2 times higher than that of KDP.     

Growth and characterization of CdSe single crystals by modified vertical vapor phase method

Good quality, large single crystals of CdSe were grown by the modified growth method (i.e., vertical unseeded vapor phase growth with multi-step purification of the starting material in the same quartz ampoule without any manual transfer between the steps). Lower temperature gradients (8–9°C/cm) at the growth interface were used for the crystal growth. As-grown CdSe crystals was characterized by X-ray diffraction, scanning electron microscopy, energy dispersive analyzer of X-rays, high-resistance instrument measurement, and etch-pit observation. It is found that there are two cleavage faces of (1 0 0) and (1 1 0) orientations on the crystal, the resistivity is about 10⁸ Ω cm, and the density of etch pits is about 10^3–4/cm². The crystal was cut into wafers and was fabricated into detectors. The detectors were tested using an ²⁴¹Am radiation source. γ-ray spectra at 59.5 keV were obtained. The results demonstrated that the quality of the as-grown crystals was good. The crystals were useful for fabrication of room-temperature-operating nuclear radiation detectors. Therefore, the modified growth technique is a promising, convenient, new method for the growth of high-quality CdSe single crystals.     

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.     

Preparation and characterizations of bulk GaN crystals

The growth conditions and mechanism of hexagonal GaN platelet crystals by Li flux were studied. The experimental results confirmed that these crystals crystallized from Li–Ga–N liquid phase. Photoluminescence (PL) spectra and Raman scattering spectrum of the crystals were obtained, which show that GaN crystals obtained by this method possess good crystalline quality.     

Studies on growth,thermal, optical,vibrational properties and hyperpolarizability of a complex orthonitroaniline with picric acid

The present article reports the growth of single crystals of a complex Orthonitroaniline with picric acid (2[C₆H₆N₂O₂]·C₆H₂(NO₂)₃OH) (ONAP) by solution growth (slow evaporation) method at room temperature. Single crystal XRD, UV–vis spectral analysis and TGA/DTA studies were carried out. FT-IR and Raman spectra were recorded to explore information of the functional groups. The high-resolution X-ray diffraction curve reveals the internal structural low angle boundaries. The PL spectrum of the title compound shows green emission. Dielectric behaviour was investigated at 33 and 70 °C. The dipole moment and first-order hyperpolarizability (β) values were evaluated by using Gaussian 98 W software package with the help of B3LYP the density functional theory (DFT) method. The possible modes of vibrations are theoretically predicted by factor group analysis. The mechanical stability of the grown crystal was tested with Vicker’s microhardness tester and the work hardening coefficient of the grown material was estimated.