Growth and characterization of a new non-linear optical l-histidinium dihydrogen phosphate single crystal

New non-linear optical single crystal of l-histidinium dihydrogen phosphate was grown by slow evaporation and temperature lowering technique from aqueous solution. Solubility studies have been carried out for three different solvents (water, acetone and ethanol). The grown crystals have been subjected to single crystal X-ray diffraction analysis to identify the cell parameters and morphology. Optical transmission spectra reveal the optical properties of the grown crystals. The NLO property of the crystal has been confirmed by Kurtz SHG test. Comparing the output power it has been confirmed that l-HDP crystals possess higher SHG efficiency than KDP. Thermal studies were carried out to check the thermal stability of the crystals.     

Electrical conductivity measurements on gel grown KDP crystals added with urea and thiourea

Pure and impurity added (with urea and thiourea) KDP single crystals were grown by the gel method using silica gels. Electrical conductivity measurements were carried out along both the unique axis and perpendicular directions at various temperatures ranging from 30 to 140‡ C by the conventional two-probe method. The present study shows that the conductivity in KDP crystals, for both the impurities considered, increases with the increase in impurity concentration and temperature. Activation energies were also determined and reported.     

Nucleation studies and surface SHG analysis of l-arginine phosphate monohydrate (LAP) family crystals

The metastable zone width and the nucleation parameters, such as interfacial tension, radius of the critical nucleus and critical free energy change have been estimated for pure l-arginine phosphate (LAP), potassium thiocynate (KSCN) mixed LAP (LAP:KSCN) and sodium sulfite (Na₂SO₃) mixed LAP LAP:Na₂SO₃ single crystals. Pure and additive mixed LAP single crystals are grown by slow cooling technique. The surface second harmonic generation (SHG) analysis is done on (100) face of the grown crystals. The SHG intensity on (100) face of the crystals are measured.     

Growth and characterization of glycinium oxalate (GOX) single crystals

Glycinium oxalate (GOX) single crystals were grown by slow cooling solution growth method. The X-ray diffraction and Fourier transform infra red studies confirm the grown crystal. The hardness values of GOX are found to be higher than glycine. The increase in hardness may be due to the C-H---O bonding. The UV-Visible studies show that GOX crystals can be used for nonlinear applications. The dielectric measurement indicates that the GOX crystals have domains of varying sizes and varying relaxation time. The SHG output of GOX was 210 mV at given pulse energy of 5 mJ/s and KDP was 240 mV.     

Growth and characterization of hexamethylenetetramine crystals grown from solution

Organic nonlinear optical single crystals of hexamethylenetetramine (HMT; 10 × 10 × 5 mm³) were prepared by crystallization from methanol solution. The grown crystals were subjected to various characterization techniques such as single crystal XRD, powder XRD, UV-Vis and electrical studies. Single crystal XRD analysis confirmed the crystalline structure of the grown crystals. Their crystalline nature was also confirmed by powder XRD technique. The optical transmittance property was identified from UV-Vis spectrum. Dielectric measurements were performed as a function of frequency at different temperatures. DC conductivity and photoconductivity studies were also carried out for the crystal. The powder second harmonic generation efficiency (SHG) of the crystal was measured using Nd:YAG laser and the efficiency was found to be two times greater than that of potassium dihydrogen phosphate (KDP).     

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.     

Surface structural investigations on (100) and (110) faces of flux-grown lanthanum borate crystals

Results of topographical studies carried out on (100) and (110) faces of lanthanum borate crystals grown from the PbO-B₂O₃ flux system are illustrated and discussed. The habit faces display the formation of cavities, microcrystals, elliptical etch pits, elliptical hillocks, circular hillocks and irregular structures. Also described are a various number of elevated structures identified as impurity phases. Energy dispersive X-ray (EDAX) studies have confirmed that these impurity phases in the growth of lanthanum borate (LaBO₃) crystals are enriched by lead (Pb). The habit faces also exhibit some elevated regions which are reported to be more imperfect in comparison with others. It is inferred that independent growth on the habit faces has taken place during the last stage of crystal growth by a two-dimensional nucleation mechanism.     

Optical, structural and electrical properties of pure and urea doped KDP crystals

Single crystals of good optical quality, made of potassium dihydrogen phosphate (KDP) doped with urea were grown by slow evaporation solution growth technique at a constant temperature of 35 °C. Optical absorption and dielectric properties were studied for pure and urea doped KDP crystals. Using powder XRD studies, crystalline nature of pure and urea doped KDP crystals was confirmed. AC conductivity was measured for the grown crystals. DC electrical conductivity and photoconductivity studies were carried out for pure and urea doped KDP crystals and the differences caused by the dopant were also discussed.     

Melt growth of novel organic nonlinear optical material and its characterization

Ethyl P-amino benzoate (EPAB) is also known as benzocaine was recently identified as new organic non linear optical (NLO) material which is having nearly six times higher SHG efficiency than that of KDP. Hence, growth of unidirectional EPAB crystal gains importance for phase matching studies and this is the first melt growth report of EPAB single crystal. Seeding with the microtube in the present technique eliminates the need for pre-grown seed and has more probability to grow bulk single crystal. Growth direction of the μT-Cz grown EPAB single crystals was identified as <100> using X-ray powder diffraction studies. Thermal properties and optical transparency of the grown material were analyzed by TG and DTA and UV-VIS spectroscopic studies respectively. Laser damage threshold study shows nearly five times high damage threshold than KDP.     

Influence of Metallic Substitutions on the Optical and Mechanical Properties of NLO Benzoyl Glycine Crystals

Benzoyl glycine （BG） is a promising organic nonlinear optical （NLO） crystal, whose second harmonic generation （SHG） efficiency is much higher than that of KDP （potassium dihydrogen phosphate）. Single crystals of pure, Cu2＋ and Cd2＋ doped BG were grown by slow evaporation technique. Optically transparent and defect free single crystals of size up to 10 mm×15 mm×10 mm were harvested in a period of 40-60 days. The growth conditions of pure and doped crystals of BG were optimized and the grown crystals were confirmed by single crystal XRD （X-ray diffraction）. The grown crystals were characterized by FTIR （Fourier transform infrared spectroscopy）, optical absorption and microhardness studies. The microhardness studies confirm that BG has a moderate VHN （Vickers hardness number） value in comparison to the.other organic NLO crystals. The efficiency of frequency doubling was measured for the using Nd：YAG laser and the results were discussed.     

UV absorption in solutions and crystals of potassium dihydrogen phosphate

The effects of impurities and growth conditions on the optical quality of potassium dihydrogen phosphate (KDP) crystals were examined. The transmittance of crystals grown under various conditions was measured in the range 200–400 nm for a larger number of impurities than previously. The highest transmittance is afforded by crystals grown from solutions with the stoichiometric composition at 55‡C and a growth rate of 1 mm per day.     

Growth of unidirectional potassium dihydrogen orthophosphate single crystal by SR method and its characterization

Unidirectional <100> potassium dihydrogen orthophosphate (KDP) single crystals were grown for the first time by Sankaranarayanan-Ramasamy (SR) method. The <100> oriented seed crystals were mounted at the bottom of the glass ampoules and the crystal of 15 mm diameter, 65 mm height were grown by SR method. The grown crystals were characterized by high-resolution X-ray diffraction (HRXRD), etching studies. The HRXRD analysis indicates that the crystalline perfection is excellent without having any very low angle internal structural grain boundaries. Dislocation density is less in SR grown KDP compared to conventional method grown KDP.     

D.C. electrical conductivity measurements on ADP single crystals added with simple organic compounds

Pure and impurity added (with urea and thiourea) ADP single crystals were grown by the free evaporation method. D.C. electrical conductivity measurements were carried out along both the unique axis and perpendicular directions at various temperatures ranging from 40–150°C by the conventional two-probe method. Activation energies were also determined. The present study indicates that the conductivity increases with the increase in impurity concentration and temperature.     

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.     

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.     

Studies on the synthesis, structure, growth and physical properties of an organic NLO crystal: 2-Amino-5-nitropyridinium Phenolsulfonate

A noncentrosymmetric crystal was prepared from 2-amino-5-nitropyridine (2A5NP) and p-Phenolsulfonic acid, which was designed for second harmonic generation. Good quality single crystals of 2-amino-5-nitropyridinium Phenolsulfonate (2A5NPP) were successfully grown by the slow evaporation method with dimensions 10 × 4 × 3 mm³. The unit cell dimensions were determined from single crystal X-ray diffraction studies. The structural perfection of the grown crystals has been analyzed by high-resolution X-ray diffraction (HRXRD) rocking curve measurements. Fourier transform infrared (FTIR) spectral studies have been performed to identify the functional groups. The optical transmittance window and the lower cutoff wavelength of the 2A5NPP have been identified by UV-vis-NIR studies. Thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) were used to study its thermal properties. Powder test with Nd:YAG laser radiation shows a high second harmonic generation. The laser induced surface damage threshold for the grown crystal was measured using Nd:YAG laser.     

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.     

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.     

Imperfections and impurity phases in flux grown RCrO3 (R = La,Yb) single crystals

Results of scanning electron microscopy (SEM) and energy dispersive X-ray analytical (EDAX) investigations, conducted on some elevated structures displayed by flux grown rare earth orthochromite, RCrO₃ (R = La, Yb) crystals, are presented. The peculiar structures exhibited by crystal surfaces indicate imperfections and impurity phases. EDAX of elevated structures reveals the various phases to be composed of lead associated materials which may probably be either Pb₂CrO₅ or Pb₂OF₂ (flux). Other secondary crystallization of impurity phases, ROF (R = La, Yb) is illustrated in the case of RCrO₃ (R = La, Yb) crystals. The elevated structures illustrate their non-stoichiometric behaviour. Precipitation of impurity phases and formation of imperfections during the growth of RCrO₃ (R = La, Yb) crystals and their effect on the crystalline quality is discussed.     

Growth and study of some gel grown group II single crystals of iodate

Single crystals of calcium iodate and barium iodate were grown by simple gel technique by single diffusion method. The optimum conditions were established by varying various parameters such as pH of gel solution, gel concentration, gel setting time, concentration of the reactants etc. Crystals having different morphologies and habits were obtained. Prismatic, dendritic crystals of barium iodate and prismatic, needle shaped, hopper crystals of calcium iodate were obtained. Some of them were transparent, some transluscent, and few others were opaque. Both the crystals were studied using XRD, FT-IR, and thermal analysis. The crystals were doped by iron impurity. The effect of doping was studied using IR spectroscopy and thermal analysis.