Studies on the growth and physical properties of nonlinear optical crystal: 2-Amino-5-nitropyridinium-toluenesulfonate

Single crystals of 2-amino-5-nitropyridinium-toluenesulfonate (2A5NPT) were grown by the slow cooling method. The unit cell dimensions were determined from single crystal X-ray diffraction studies. The thermal parameters - thermal diffusivity (α), thermal effusivity (e), thermal conductivity (K) and heat capacity (C_p) of 2A5NPT were measured by an improved photopyroelectric technique at room temperature. Single and multiple shot experiments performed on the grown crystals for the second harmonic of pulsed Nd:YAG laser (532 nm) show that it exhibits a high laser damage threshold which is a favorable property for nonlinear optical applications. Dielectric constant and dielectric loss of the grown crystal were evaluated for the frequency range 1 kHz-1 MHz in the temperature region 40-130 °C. Hardness values were measured using Vickers hardness measurement.     

Synthesis, structure, growth and physical properties of a novel organic NLO crystal: 1,3-Dimethylurea dimethylammonium picrate

A novel noncentrosymmetric crystal was prepared from 1,3-dimethylurea dimethylammonium picrate, C₁₁H₁₈N₆O₈ (DMUP), which was designed for second harmonic generation. DMUP crystals exist in noncentro symmetric space group Cmc2₁ with unit cell dimensions a = 14.288(4) Å, b = 17.023(5) Å, c = 6.8268(13) Å, α = β = γ = 90° and volume = 1660.5(8) Å³. The crystal structure of DMUP has been determined using single crystal X-ray diffraction studies. The single crystals of DMUP were successfully grown by the slow evaporation method with dimensions 10 mm × 4 mm × 3 mm using dimethylformamide as solvent. The structural perfection of the grown crystals has been analysed by High-resolution X-ray diffraction (HRXRD) rocking curve measurements. Powder test with Neodymium-doped Yttrium aluminum garnet (Nd:YAG) laser radiation shows a high second harmonic generation (SHG). The laser induced surface damage threshold for the grown crystal was measured using Nd:YAG laser.     

Crystal structure and characterization of a novel organic crystal: 4-Dimethylaminobenzophenone

Single crystals of a novel organic material, dimethylaminobenzophenone were grown from aqueous solution employing the technique of controlled evaporation. Dimethylaminobenzophenone belongs to the monoclinic system, with a = 12.5755(7) Å, b = 7.9749(4) Å, c = 13.0946(7) Å, α = 90°, β = 111.6380(10)° and γ = 90°. Fourier transform infrared study has been performed to identify the functional groups. The transmittance of dimethylaminobenzophenone has been used to calculate the refractive index n; the extinction coefficient K and both the real ?_r and imaginary ?_i components of the dielectric constant as functions of photon energy. The optical band gap of dimethylaminobenzophenone is 2.9 eV. The structural prefection of the grown crystals has been analyzed by high-resolution X-ray diffraction rocking curve measurements. Thermo gravimetric analysis and differential thermal analysis have also been carried out, and the thermal behavior of dimethylaminobenzophenone crystal has been studied. The dielectric properties and mechanical properties have been investigated.     

Crystal structure and characterization of a novel organic optical crystal: 2-Aminopyridinium trichloroacetate

2-Aminopyridinium trichloroacetate, a novel organic optical material has been synthesized and crystals were grown from aqueous solution employing the technique of controlled evaporation. 2-Aminopyridinium trichloroacetate crystallizes in monoclinic system with space group P2₁/c and the lattice parameters are a = 8.598(5) Å, b = 11.336(2) Å, c = 11.023(2) Å, β = 102.83(1)° and volume = 1047.5(3) Å³. High-resolution X-ray diffraction measurements were performed to analyze the structural perfection of the grown crystals. Thermal analysis shows a sharp endothermic peak at 124 °C due to melting reaction of 2-aminopyridinium trichloroacetate. UV-vis-NIR studies reveal that 2-aminopyridinium trichloroacetate has UV cutoff wavelength at 354 nm. Dielectric studies show that dielectric constant and dielectric loss decreases with increasing frequency and finally it becomes almost a constant at higher frequencies for all temperatures. The negative nonlinear optical parameters of 2-aminopyridinium trichloroacetate were derived by the Z-scan technique.     

Studies on growth and characterization of an NLO crystal: L-alanine hydrogen chloride (LAHC)

A nonlinear optical (NLO) salt viz. L-alanine hydrogen chloride (LAHC) has been synthesized and solubility of the synthesized salt in de-ionized water was determined at different temperatures. Single crystals of L-alanine hydrogen chloride (LAHC) salt were grown by solution method with slow evaporation technique. The grown crystals were characterized by single crystal X-ray diffraction (XRD) and powder XRD analyses to study the crystal structure. The crystallinity of LAHC crystal was confirmed by the powder X-ray diffraction study and diffraction peaks were indexed. FTIR study was used to confirm the presence of various functional groups in the grown crystals. UV–visible transmittance spectrum was recorded to study the optical transparency of LAHC crystal. The nonlinear optical (NLO) property of the grown crystal was confirmed by Kurtz–Perry powder test. The density of LAHC crystal was determined by floatation method. The mechanical strength of the crystal was estimated by Vickers hardness test. The grown crystals were subjected to TG/DTA analyses. The dielectric behavior of the sample was also studied.     

Investigation on growth and characterization of a new inorganic NLO material: Zinc sulphate (ZnSO4:7H2O) doped with Magnesium Sulphate (MgSO4:7H2O)

Single crystal of Zinc sulphate doped with Magnesium sulphate, a nonlinear material, was grown from aqua solution by slow evaporation method at room temperature. Good quality single crystals were grown by slow evaporation technique (four weeks) and the crystals subjected to single crystal X-ray diffraction and FT-IR analyses to confirm the formulation of new crystals. The TGA and DTA reveal that the material has good thermal stability. The UV-Vis spectrum confirms that the material has wide optical transparency and the existence of the second harmonic generation has also been ascertained by Kurtz powder method.     

Growth and characterization of organic material 2-hydroxypyridine single crystal by modified vertical Bridgman technique

Large size (15 mm diameter and 80 mm length) organic material 2-hydroxypyridine single crystal has been grown using the double wall ampoule with nano translation by modified vertical Bridgman technique for the first time. Material of the grown crystal was confirmed by single and powder X-ray diffraction (XRD) measurements. Fourier transform infrared (FTIR) analysis was used to identify the functional groups present in the grown crystal. High resolution X-ray diffraction (HRXRD) has been performed to analyze the crystalline perfection of the grown single 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 at various temperatures ranging from 308 to 373 K and the results indicate an increase in the dielectric parameters with the increase of temperature at all frequencies. The second harmonic generation (SHG) studies were used to analyze the nonlinear optical property of the grown crystal.     

Growth, spectroscopic properties and laser performance of Nd-doped potassium ytterbium tungstate laser crystal

The 5 at.% Nd³⁺-doped potassium ytterbium tungstate (Nd³⁺:KYb(WO₄)₂, hereafter Nd:KYbW) laser crystal with the dimension up to 28 mm × 15 mm × 12 mm was grown by the top seeded solution growth (TSSG) method. The infrared spectrum of crystal sample was measured, and the vibrational peaks were assigned. According to the absorption and emission spectra of crystal sample, the absorption and emission cross-sections are 16.03 × 10⁻²⁰ cm² at 808 nm and 10.72 × 10⁻²⁰ cm² at 1067 nm, respectively. The fluorescence life of ⁴F_3/2 energy level is 196.33 μs, and the fluorescence branching ratio for the ⁴F_3/2-⁴I_11/2 transition at 1067 nm is 55.74%. The energy transfer between Nd³⁺ and Yb³⁺ ions was observed from the fluorescence spectra pumped by 808 and 980 nm LD sources and the Stark levels of Yb³⁺ in Nd:KYbW crystal were determined. Highly efficient laser output up to 305 mW of Nd:KYbW crystal at 1067 nm has been achieved under pumping by a CW 808 nm laser diode at room temperature. The optical-optical conversion efficiency is 33.9% and the slope efficiency is 46.8%.     

Synthesis, crystal growth and characterization of organic material: N-Bromosuccinimide (NBS) for NLO applications

The organic nonlinear optical crystal of N-Bromosuccinimide (NBS) was grown by slow cooling solution growth technique using methanol as solvent. Single crystal and powder X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectral analyses were carried out to confirm the NBS crystals. The ultra violet (UV)-Visible and photoluminescence spectral studies were carried out, the green band at 2.02 eV can be attributed to radiative recombination between deep donors and shallow acceptors. The second harmonic generation (SHG) behaviour of NBS was tested by Kurtz-Perry powder technique. The hardness behaviour, laser damage threshold and dielectric characteristics of NBS crystals were studied.     

Growth and characterization of the nonlinear optical single crystal: l-Lysinium trifluoroacetate

A novel organic nonlinear optical (NLO) crystal, l-lysinium trifluoroacetate (with the molecular formula as (H₃N)⁺CH₂CH₂CH₂CH₂CH(H₃N)⁺COO⁻CF₃COO⁻), was grown by the controlled evaporation of its aqueous solution. The X-ray powder diffraction was used to determine its cell parameters. The calculated results based on the diffraction data reveal that l-lysinium trifluoroacetate belongs to the monoclinic crystallographic system, space group P2₁, with cell parameters: a = 5.698(5), b = 23.542(8), c = 8.500(6) Å, β = 91.62(9)°, V = 1139.96 Å³. The grown crystals were characterized by the elemental analyses, Fourier transform infrared and Raman spectra. Experiments of thermogravimetric (TG) and differential thermal analysis (DTA) were carried out to study its thermal properties. The optical behaviours, including transmission spectrum and second harmonic generation (SHG), were investigated to study its linear and nonlinear optical properties. Optical nonlinearities were analyzed and discussed involved with its crystal structure.     

Studies on the growth, structural, optical, mechanical properties of 8-hydroxyquinoline single crystal by vertical Bridgman technique

Single crystal of organic nonlinear optical material, 8-hydroxyquinoline (8-HQ) of dimension 52 mm (length) × 12 mm (dia.) was grown from melt using vertical Bridgman technique. The crystal system of the material was confirmed by powder X-ray diffraction analysis. The crystalline perfection of the grown crystal was examined by high-resolution X-ray diffraction study. Low angular spread around 400″ of the diffraction curve and the low full width half maximum values show that the crystalline perfection is reasonably good. The recorded photoluminescence spectrum shows that the material is suitable for blue light emission. Optical transmittance for the UV and visible region was measured and mechanical strength was estimated from Vicker's microhardness test along the growth face of the grown crystal.     

Structural and morphological characterization of flux grown YTa7O19, Nd:YTa7O19, Nd:LaTa7O19 and NdTa7O19 crystals

YTa₇O₁₉ (YHT), Nd:YTa₇O₁₉ (Nd:YHT), Nd:LaTa₇O₁₉ (Nd:LHT) and NdTa₇O₁₉ (NHT) single crystals have been grown by spontaneous nucleation from high-temperature solutions using K₂Mo₃O₁₀-B₂O₃ as a flux and structurally characterized by X-ray diffraction techniques. The effect of the flux composition on the crystal morphology is discussed. The distribution of the Nd³⁺ ions in doped crystals has been investigated by electron microprobe analysis, evidencing non-uniform segregation coefficients. The Raman spectra of the investigated compounds are presented, and a reinterpretation of the fine structure present in the optical spectra is proposed in the light of the crystallographic information.     

Crystal structure,crystal growth and characterization of novel organic NLO material: 2,4,4′-Trimethoxybenzophenone

Single crystals of 2,4,4′-Trimethoxybenzophenone (TMB) were grown by slow evaporation solution growth technique using acetone as a solvent. TMB crystallizes in monoclinic system with noncentrosymmetric space group, P2₁, and the cell parameters are a = 8.485(5) Å, b = 8.173(5) Å, c = 10.254(5) Å, β = 102.085(5)° and V = 695.3(7) Å³. Gaussian 98W has been used to calculate the first-order hyperpolarizability of TMB. Fourier transform infrared (FTIR) spectroscopic studies were performed for the identification of different modes present in the compound. TMB crystals are transparent in the entire visible region and have a lower optical cutoff at 400 nm. The powder second harmonic generation efficiency of TMB was determined to be 6 times that of urea. The observed SHG response for TMB is due to effective charge transfer arising from the donor–π–acceptor–π–donor (D–π–A–π–D) structure of the molecule. From the thermogravimetric/differential thermal analysis, the TMB was found to be thermally stable up to 79 °C. The dielectric and mechanical properties of the TMB were also studied.     

Growth and characterization of metal ions and dyes doped KDP single crystals for laser applications

The organic dyes (Amaranth, Rhodamine B and Methyl Orange) are doped in Potassium Dihydrogen Phosphate crystals. Influences of supersaturation and dye concentration in the solution, on the color and crystal habit of Potassium Dihydrogen Phosphate, were observed. Amaranth in the solution at low super saturation and high dye concentration colored the pyramidal section (1 0 1) of the crystals. The highly super saturated solutions produce entirely colored crystals. Dyes doped Potassium Dihydrogen Phosphate crystals were also grown by solution growth technique. The concentration of dopants in the mother solution was varied from 0.1 to 10 mol%. The studies on pure and doped Potassium Dihydrogen Phosphate crystals clearly indicate the effect of dopants on the crystal structure, in the absorption of IR frequencies and the non-linear optical property. The frequencies with their relative intensities are obtained in Fourier Transform-Infrared spectra of pure and doped Potassium Dihydrogen Phosphate. The very weak bands for dopants indicate its presence in low concentration. The absence of even such a weak band in the case of Potassium Dihydrogen Phosphate doped with Amaranth indicates the strong interaction with O-H groups. The calculated IR frequency 3333 cm⁻¹ for O-H stretching was in close agreement with the experimentally obtained one for pure Potassium Dihydrogen Phosphate at 3340 cm⁻¹.The doped crystals show good second harmonic generation efficiency. The dopants increase the hardness value of the material, which also depends on the concentration of the dopants. Dye doping improves the Nonlinear Optical properties of the grown crystals. Results of the growth kinetics of Potassium Dihydrogen Phosphate crystals in the presence of impurities are also discussed.     

Crystal growth, thermal and optical studies of semiorganic nonlinear optical material: l-lysine hydrochloride dihydrate

Single crystals of l-lysine hydrochloride dihydrate (LLHCD), a nonlinear optical material, have been grown by slow cooling technique from its aqueous solution. LLHCD was found to be highly soluble in water. The grown crystals have been subjected to single crystal X-ray diffraction to confirm the structure and to estimate the lattice parameters. The vibrational structure of the molecule is elucidated from FTIR spectra. Thermal analysis revealed the thermal stability of the grown crystals. The optical transmittance spectrum shows that the material possesses good optical transparency in the entire visible region with a UV cut-off wavelength at 228 nm. The mechanical properties of the grown crystal have been studied using Vicker's microhardness test. The laser damage threshold of 52.25 MW/cm² has been measured by irradiating Q-switched Nd:YAG laser (1064 nm).     

Investigation on the nucleation kinetics of antiferroelectric ADP admixtured ferroelectric TGS crystals

Induction period and interfacial energy have been determined for the aqueous solution growth of ammonium dihydrogen orthophosphate admixtured triglycine sulphate. It is observed that the induction period decreases exponentially with supersaturation and hence the nucleation rate increases with the increase of supersaturation. The solubility of synthesized ADPTGS has been estimated at different temperatures. ADPTGS has a positive temperature coefficient of solubility. Nucleation parameters such as radius of the critical nucleus, number of molecules in the critical nucleus and critical free energy change have also been investigated.     

Mechanical,thermal and laser damage threshold analyses of II group metal complexes of thiourea

Single crystals of thiourea metal complexes with selected Group II metal ions, Zinc and Cadmium, have been grown by solvent evaporation technique. The crystals grown are bisthiourea zinc chloride (BTZC) and bisthiourea cadmium chloride (BTCC). Following an improved photopyroelectric technique, the thermal transport properties have been determined. It is found that BTCC has a higher heat capacity (304.09 J kg⁻¹ K⁻¹) than BTZC (255.24 J kg⁻¹ K⁻¹), and hence BTCC has better thermal stability. Vicker's microhardness measurements reveal that these materials have reverse indentation size effect and belong to the category of soft materials. Elastic stiffness is found to be higher for BTCC (1.57 GPa) than BTZC (0.76 GPa). The roles of the Group II metal ions in improving the mechanical and thermal stability of the metal complexes are discussed. Multi-shot laser damage studies on these materials reveal that BTCC has a higher laser damage threshold (15 GW cm⁻²) than BTZC (6 GW cm⁻²).     

Synthesis of the nanocrystalline CoFe2O4 ferrite thin films by a novel sol-gel method using glucose as an additional agent

Polycrystalline and nanometer-sized CoFe₂O₄ ferrite thin films are successfully synthesized using glucose as an addition agent. The thermal gravimetric/differential thermal analyzer, X-ray diffractometer, electron diffraction, scanning electron microscope, atomic force microscope and vibrating sample magnetometer are used to characterize the effects of the calcination temperature on the crystalline structure, morphology and magnetic properties of the Co-ferrite thin films. CoFe₂O₄ ferrite thin films have a single phase inverse spinel structure and are crystallized at and above 300 °C which is much lower than the required temperature in the traditional ceramic method (about 500-600 °C). Co-ferrite thin films annealed at relative low temperature of 400 °C show very small particle size with average of 32 nm and excellent magnetic properties for information storage applications.     

Optical properties of Ho:SrMoO4 single crystal

Ho³⁺:SrMoO₄ single crystal was grown by the Czochralski method in N₂ atmosphere. The polarized absorption spectra, emission spectra and the lifetime decay curves were measured at room temperature. The Judd-Ofelt theory has been applied to analyze the absorption spectra. The spectroscopic parameters, including three intensity parameters, radiative transition rates, radiative lifetimes, fluorescent branching ratios and emission cross sections were obtained. The luminescence lifetime of the ⁵S₂ level was determined to be 4.40 μs.     

The first bulk synthesis of ReO3-type tungsten trioxide, WO3, from nanometric precursors

A perovskite form of WO₃ has been synthesized in bulk for the first time at 0.66 GPa and 973 K with a=3.7823(4) Å [a₀=3.7719(4) Å, at ambient conditions] from nanometric powder of WO₃ with an average crystallite size of 35 nm. Data collected during tests to determine both the likelihood of retaining the structure at room temperature and the effect of high pressure on distortion have afforded analysis of thermal expansivity and compressibility of this phase. These result in V_T=53.407(5)exp(−3.9(12)×10⁻⁶(T−298)+1.91(9)×10⁻⁸(T²−298²)) Å³ and equation of state parameters of V₀=53.67(4) Å³, K₀=41.8(19) GPa with ∂K/∂P=K′=5.6(12).