A comparative analysis on growth aspects and characterization of novel benzophenone derivatives

The growth aspects of two benzophenone derivatives such as 4-4′ dimethylbenzophenone (4-4′ DMBP) and 4-amino benzophenone (4-ABP) were investigated based on solute–solvent interactions in the growth medium. The structural, mechanical and optical properties of the two derivatives were comparatively investigated. It was found that the 4-ABP crystal was relatively harder compared to 4-4′ DMBP. The optical transmission study showed that the 4-4′ DMBP sample has high transparency especially in the UV region as it had the cut-off wavelength of 331 nm. On the other hand, the 4-ABP crystal has relatively low transparency in the visible region with the cut-off wavelength of 400 nm. The 4-4′ DMBP sample exhibited the SHG efficiency of 1.5 times that of KDP whereas the 4-ABP sample exhibited the SHG efficiency of 161 times that of KDP. The optical properties of the derivatives were discussed in relation with the molecular structure of the materials.     

Growth by SR method and characterization of bis(thiourea)zinc(II) chloride single crystals

Large size single crystals of bis(thiourea)zinc(II) chloride (BTZC), a potential nonlinear optical material, have been grown successfully by the Sankaranarayanan-Ramasamy (SR) method. Powder X-ray diffraction and Fourier transform infrared analyses confirmed the material of the grown crystal. Thermal stability was assessed by the thermogravimetric/differential thermal analysis. The high-resolution X-ray diffraction and dielectric measurements indicate that the crystal grown by the SR method has good crystalline perfection and low density of defects.     

Third harmonic generation in LiKB4O7 single crystal

The third order nonlinear optical properties of the lithium potassium borate (LiKB₄O₇) single crystal have been investigated by means of the rotational Maker fringe technique using Nd:YAG laser at 1064 nm working in picosecond regime. The value of the third order nonlinear optical susceptibility was calculated using the theoretical model of Kajzar et al. and was found to be about 1.4 × 10⁻²¹ m² V⁻² that is one order higher than that of fused silica.     

Effect of Ni on the structural, optical, thermal and dielectric properties of ADP single crystals

The effects of the addition of Ni²⁺ on the growth and various properties of ammonium dihydrogen phosphate single crystals grown from aqueous solution by the slow evaporation method have been studied. The grown crystals were subjected to HRXRD, UV-Vis, TG/DTA and dielectric studies. The structural perfection of the grown crystal has been analyzed by high resolution X-ray diffraction rocking curve measurements. UV-Vis studies show that the grown crystal has good transparency in the entire visible region which is an essential requirement for a nonlinear crystal. Higher decomposition temperature was observed from TG/DTA. Dielectric constant and dielectric loss were measured for the grown crystal for different frequencies and temperatures.     

Growth and optical properties of (Yb3−xYx)Al5O12:Ce single crystals

To improve the infrared emission of Yb³⁺ ions doped in the garnet host Y₃Al₅O₁₂ (YAG) single crystal through the energy transfer from Ce³⁺ to Yb³⁺ ions, the 〈1 1 1〉-oriented YAG:Ce³⁺, YAG:Yb³⁺, YAG:(Ce³⁺, Yb³⁺) and Yb₃Al₅O₁₂:Ce³⁺ (YbAG:Ce³⁺) single crystals were grown using the Czochralski Method, respectively. The excitation and emission spectra of these garnet single crystals were characterized. In YAG:Ce³⁺ crystal, the yellow emission of Ce³⁺ ions present, but it was completely extinguished in YAG:(Ce³⁺, Yb³⁺) crystal and YbAG:Ce³⁺ crystal. However, the characteristic absorption bands of Ce³⁺ still existed in the excitation spectrum of Yb³⁺ ions, which showed that the energy absorbed by Ce³⁺ ions can be transferred to Yb³⁺ ions for its infrared emission.     

Crystal growth and characterization of Deuterated Glycine Phosphite single crystals

Deuterated Glycine Phosphite single crystals were grown by low temperature solution growth method using high purity deuterated water as solvent. Deuteration content of the as grown crystals was improved by repeated recrystallisation process. Structural perfection, transparency and the functional groups present in the grown crystals were identified using different characterization analyses. Dielectric behaviors of the as grown specimens were examined through thermal and impedance analysis. Partial deuteration of the grown crystal was confirmed from the DSC and dielectric results.     

Anisotropy of the spectroscopy properties of the wurtz-stannite Cu2ZnGeS4 single crystals

In this study, the near band edge anisotropic optical properties of wurtz-stannite (WS) Cu₂ZnGeS₄ single crystals were characterized using polarization-dependent transmittance and electrolyte electroreflectance (EER) techniques. Single crystals of Cu₂ZnGeS₄ were grown by chemical vapor transport method using iodine as a transport agent. Analysis of absorption spectra revealed indirect allowed transitions for Cu₂ZnGeS₄ with the band gaps of 2.02 (2.07) and 2.08 (2.14) eV for E‖b and Е‖a polarization configurations at 300 (10) K. The room-temperature EER spectra in the vicinity of the direct band edge showed anisotropic transitions at around 2.38, 2.44 and 2.45 eV for E‖b, Е‖a and Е‖c polarizations, respectively. Based on the experimental observations and recent band-structure calculations a plausible band diagram near band edge of WS-Cu₂ZnGeS₄ was constructed.     

Effects of polarized excitation on the PJ manifolds emission in KYF4:Pr single crystal

A room temperature spectroscopic investigation on KYF₄:1.25 at%Pr³⁺ is presented. The effects on the optical properties of the multisite-disordered nature of the sample are studied and discussed. In particular we report on the broadening of the ³P_J absorption lines, at 10 and 300 K, and the 450–770 nm emissions as a function of observation and pump polarization. The evidence of a peculiar difference between emission under polarized excitation, parallel or orthogonal to the c axis, is shown. The ³P₀ lifetime was 45 μs in agreement with that measured in other fluoride hosts.     

Laser patterning and morphology of two-dimensional planar ferroelastic rare-earth molybdate crystals on the glass surface

The laser-induced crystallization method is applied to pattern two-dimensional planar crystals consisting of ferroelastic β′-(Sm,Gd)₂(MoO₄)₃ crystals (designated here as SGMO crystals) on the surface of Sm₂O₃–Gd₂O₃–MoO₃–B₂O₃ glass. By scanning Yb:YVO₄ fiber lasers (wavelength: 1080 nm) continuously with a small pitch (0.7 μm) between laser irradiated parts, planar SGMO crystals with periodic domain structures showing different refractive indices are patterned successfully, and a high orientation of SGMO crystals is confirmed from micro-Raman scattering spectrum and second harmonic intensity measurements. It is found that the crystal growth direction is perpendicular to the laser scanning direction. This relation, i.e., the perpendicular relation, is a different from the behavior in discrete crystal line patterning, where the crystal growth direction is consistent with the laser scanning direction. The present study proposes the possibility of the control of crystal growth direction in laser-induced crystallization in glasses.     

Generation of annularly symmetric periodic ferroelectric domains in Nd doped near stoichiometric LiTaO3 crystals by the vapor transport equilibration processing

Annually symmetric periodic ferroelectric domain and near stoichiometry have been generated simultaneously from Nd-doped congruent LiTaO₃ crystals by using the vapor transport equilibration (VTE) processing for the first time. The periodic width in the domain structure of 0.5 mol% Nd doped stoichiometric LiTaO₃ crystal was found to be about 70 μm, and the wavelength decreased with the increasing Nd concentration. It can be noticed by transmission spectra that VTE treated LT crystals shows blue shift as compared to congruent LT crystals. Also, various absorption bands were observed in Nd-doped LiTaO₃ crystals corresponding to the transitions from ⁴I_9/2 ground state of Nd³⁺ ions, indicating its potential in the self-lasing quasi-phase matching (QPM) applications.     

Investigation of SR method grown 0 0 1 directed KDP single crystal and its characterization by high-resolution X-ray diffractometry (HRXRD), laser damage threshold, dielectric, thermal analysis, optical and hardness studies

0 0 1 directed potassium dihydrogen orthophosphate (KDP) single crystal was grown by Sankaranarayanan–Ramasamy (SR) method. The 0 0 1 oriented seed crystals were mounted at the bottom of the platform and the size of the crystals were 10 mm diameter, 110 mm height. Two different growths were tried, in one the crystal diameter was the ampoule's inner diameter and in the other the crystal thickness was less than the ampoule diameter. In the first case only the top four pyramidal faces were existing whereas in the second case the top four pyramidal faces and four prismatic faces were existing through out the growth. The crystals were grown using same stoichiometric solution. The results of the two growths are discussed in this paper. The grown crystals were characterized by high-resolution X-ray diffractometry (HRXRD), laser damage threshold, dielectric, thermal analysis, UV–vis spectroscopy and microhardness studies. The HRXRD analysis indicates that the crystalline perfection is excellent without having any very low angle internal structural grain boundaries. Laser damage threshold value has been determined using Nd:glass laser operating at 1054 nm. The damage threshold for the KDP crystal is greater than 4.55 GW cm⁻². The dielectric constant was higher and the dielectric loss was less in SR method grown crystal as against conventional method grown crystal. In thermal analysis, the starting of decomposition nature is similar in SR method grown KDP crystal and conventional method grown crystal. The SR method grown KDP has higher transmittance and higher hardness value compared to conventional method grown crystals.     

Growth by SR method and characterization of hippuric acid single crystals

The potential organic nonlinear optical material of hippuric acid (HA) has been grown by novel unidirectional solution growth method using dimethyl formamide (DMF) as the solvent. The crystal system has been identified and lattice dimensions have been measured from the single crystal X-ray diffraction analysis. The crystalline perfection has been evaluated by high resolution X-ray diffraction (HRXRD) technique and found that the crystal quality is reasonably good. However, it contains a low angle structural grain boundary. The relative second harmonic generation (SHG) has been tested using Kurtz powder technique and found to be 1.54 times higher than that of potassium dihydrogen phosphate (KDP) single crystal. Its optical character has been assessed by UV-Vis. analysis and found that there is no absorption in the entire visible region.     

Flux growth of KGaP2O7 single crystals

Transparent potassium gallium pyrophosphate single crystals, KGaP₂O₇, have been grown by a spontaneous nucleation method using K₄P₂O₇-4KPO₃ as flux. The as-grown crystals were characterized by X-ray powder diffraction (XRPD), differential thermal analysis (DTA) and thermo-gravimetric analysis (TGA) techniques. The results show that the as-grown crystals were well crystallized and indexed in a monoclinic crystal system with space group P2₁/c. The crystal is stable in the measurement temperature range of 25-939.9 °C, and it melts congruently at 947 °C. The frequencies of the vibrational modes of the crystal were also obtained from measurements of the infrared spectrum.     

Growth and properties of benzil doped benzimidazole (BMZ) single crystals

In the present work, we have made an attempt to study the effect of benzil doping on the properties of benzimidazole single crystals. For this purpose we have grown pure and benzil doped benzimidazole single crystals by vertical Bridgman technique. The grown crystals were characterized by various characterization techniques. The presence of dopants confirmed by powder X-ray diffraction (XRD). Crystalline perfection of the grown crystals has been analysed by high-resolution X-ray diffraction (HRXRD). The transmittance, electrical property and mechanical strength have been analysed using UV-vis-NIR spectroscopic, dielectric and Vicker's hardness studies. The relative second harmonic generation efficiency of pure and doped benzimidazole crystals measured using Kurtz powder test.     

Yb-doped NaBi(WO4)2 fibre single crystals grown by the micro-pulling down technique and emission spectroscopic characterization

NaBi_1−xYb_x(WO₄)₂ fibres single crystals were successfully grown by micro-pulling down technology (MPD). The Yb³⁺-doped NaBi(WO₄)₂ fibres single crystals have been pulled using MPD technique with controlled diameter and stationary stable growth conditions corresponding to flat crystallization interface with meniscus length equal to the fibre radii and pulling rate range [6-48 mm h⁻¹]. We have determined the monophased field of NaBi_1−xYb_x(WO₄)₂ for x ≤ 0.3. The lattices parameters decrease as a function of Yb³⁺ substitution in Bi³⁺ sites. The melt behaviour has been study by DTA/TG analysis. We have found that the stoichiometric compounds NaBi(WO₄)₂ melt congruently at 935 °C. The fibre diameters varied from 0.5 to 1 mm depending on the capillary die diameter, pulling rate and the molten zone temperature. Complementary Yb³⁺ spectroscopic characterization in the NaBi(WO₄)₂ lattice has been done by IR emission measurements under laser pumping at room temperature.     

Growth and time dependent alignment of KCl crystals in Hemoglobin LB monolayer

Nature and organism often use the biomineralization technique to build up various highly regular structures such as bone, teeth, kidney stone etc., and recently this becomes the strategy to design and synthesis of novel biocomposite materials. We report here the controlled crystallization of KCl in Langmuir and Langmuir Blodgett (LB) monolayer of Hemoglobin (Hb) at ambient condition. The nucleation and growth of KCl crystals in Hb monolayer has temporal and KCl concentration dependency. The growth of KCl crystals in LB film of Hb has distinct behavior in the alignment of crystals from linear to fractal like structures depending on growth time. The crystallographic identity of the biomineralized KCl crystal is confirmed from HR-TEM, XRD, and from powder diffraction simulation. Our results substantiated that the template of Langmuir monolayer of proteins plays a crucial role in biomineralization as well as in designing and synthesizing of novel biocomposite materials.     

Electron spin resonance and AC susceptibility studies on La0.9Pb0.1MnO3 single crystals

Phase separation has been recognized as important properties of manganite to create colossal magnetoresistance (CMR). Frequency dependence of AC susceptibility and electron spin resonance (ESR) studies confirm the phase separated glassy magnetism in the La_0.9Pb_0.1MnO₃ crystals. ESR spectra exhibit a gradual narrowing of the asymmetric FMR signals upon increasing the temperature and approaching the Curie temperature (T_c). The temperature dependence of line width (ΔH_pp), g-factor, double integrated (I) intensity of the resonance signals and frequency dependence peak temperatures are discussed in this paper to explain inhomogeneity in the La_0.9Pb_0.1MnO₃ single crystals.     

Optical,mechanical and transport properties of unidirectional grown l-tartaric acid bulk single crystal for non-linear optical application

Good optical quality bulk single crystal of l-tartaric acid has been grown by directional solidification crystal growth method from aqueous solution. Crystal of dimension 77 mm length and 12 mm diameter has been grown at a growth rate of 2.5 mm day⁻¹ which is the maximum size and growth rate achieved so far. The grown crystal was confirmed by powder XRD analysis and the presence of the functional groups in the crystal lattice was confirmed by Fourier transform infrared spectral analysis. Transmission spectral analysis shows that the crystal has more than 90% of transmittance in visible and near infrared region which exhibits the good optical quality of the crystal. The optical band gap was estimated to be 4.8 eV and it shows indirect optical transition. Thermal analysis shows the crystal to be thermally stable up to 172 °C and the load variation of the hardness has been explained on the basis of normal indentation size effect from microhardness study.