Synthesis,Growth and Spectroscopic Studies of Piperazinium Paranitrophenolate Monohydrate Crystals

A new piperazinium 4-nitro phenolate monohydrate single crystal (PNP) was grown by employing the solution growth technique piperazine and 4-nitrophenol, were the source material used for the growth, acetonitrile is used as solvent. The grown crystal was characterized by Single X-ray analysis and it shows that piperazinium 4-nitrophenol monohydrate crystallizes in the monoclinic space group P2 1/c, with cell parameters a=10.902 5(4) Å, b=6.226 1(3) Å, c=14.031 8(5) Å, and z=4. The lattice parameters of the substances were also determined by using powder diffraction methods. The functional groups are identified by using FTIR spectral analysis. The absorbance of title compound were analyzed using UV-Vis spectra. The thermo analytical properties of the crystal were studied using TG, DTA.     

Synthesis,structural characterization,Hirshfeld surface analysis,spectroscopic and ferroelectric properties studies of 4-methylbenzylammonium sulfate

Single crystals of 4-methylbenzylammonium sulfate were grown in an aqueous solution at room temperature. The grown compound is characterized by spectroscopic, thermal, and dielectric studies and its structure was determined by single-crystal X-ray diffraction analysis. Its crystal structure is described as a three-dimensional network where the sulfate anions (HSO₄^?) are interconnected through H-bonds to form anionic layers between which the 4-methylbenzylammonium cations are located. The hydrogen bonding network connecting the different components is given. Hirshfeld surface analysis was performed to visualize, explore and quantify intermolecular interactions in the crystal lattice. This analysis revealed the presence of H…C/H…C, C…O/O…C intermolecular interactions and O…O, H…H short contacts in the crystal. X-ray, structural and electrical results are correlated. The kind of the observed conduction is protonic by translocation. Differential scanning calorimetry (DSC) shows that this material presents a reversible phase transition at 390 K, confirmed by the dielectric permittivity study.     

Investigation on growth of 4-N,N-dimethylamino-N′-methylstilbazolium p-chlorobenzenesulfonate: An efficient organic NLO crystal with potential THz properties

The growth of an efficient organic nonlinear optical material 4-N, N-dimethylamino-N′-methylstilbazolium p-chlorobenzenesulfonate (DASC), a derivative of the stilbazolium tosylate family has been reported by employing the slope nucleation method coupled with slow solvent evaporation. The crystal system and lattice parameters are estimated by single crystal X-ray diffraction. The second harmonic conversion efficiency of DASC was determined using the Kurtz and Perry powder technique. The thermal stability of the compound is determined by thermo gravimetric/differential thermo gravimetric (TG/DTG) and differential scanning calorimetric (DSC) techniques. The hardness profile of the sample is investigated by Vickers microhardness test. The dielectric constant and dielectric loss of the crystal were studied as function of frequency. The surface properties of DASC are reported by undertaking scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies.     

Polymer Dynamics in Polyurethane/clay Nanocomposites Studied by Dielectric and Thermal Techniques

Differential scanning calorimetry (DSC), broadband dielectric relaxation spectroscopy (DRS), and thermally stimulated depolarization current (TSDC) techniques were employed to investigate glass transition and polymer dynamics in nanocomposites of polyurethane (PU) and organically modified montmorillonite (MMT) (weight fraction 0%–15%) prepared by solution casting. The PU matrix was obtained from oligo(oxytetramethylene glycol) of molar mass 1000 g/mol, 4,4′-diphenylmethane diisocyanate and 1,1-dimethylhydrazine as chain extender. Wide-angle X-ray scattering confirmed the formation of partly exfoliated structures at low MMT content. DSC, DRS, and TSDC show, in agreement with each other, that a fraction of polymer makes no contribution to the glass transition and to the corresponding α relaxation, whereas the rest exhibits similar glass transition dynamics as the pure matrix. This fraction of immobilized polymer reaches a maximum at about 5 wt% MMT. Effects of MMT on the microphase-separated structure of PU are negligible, as indicated by the study of glass transition and interfacial dielectric polarization/relaxation. No effects of MMT on the local, secondary γ and β relaxations were observed. Mechanical properties show a maximum improvement at about 5 wt% MMT, in good correlation with morphology and dynamics.     

A study of thermal, dielectric and magnetic properties of strontium malonate crystals

Crystals of strontium malonate (SrC₃H₂O₄) were grown in silica gel by the single diffusion technique. The thermo gravimetric (TG), differential thermal analysis (DTA) and differential scanning calorimetric (DSC) studies were carried out to investigate the thermal stability of the crystal. The dielectric behavior of the title compound crystal was investigated by measuring the dielectric parameters - dielectric constant, dielectric loss and AC conductivity as a function of four frequencies −1 kHz, 10 kHz, 100 kHz and 1 MHz at temperatures ranging from 50 to 170 °C. Results indicate that the title compound is thermally stable up to about 409 °C and is a promising low ε_r-value dielectric material. The magnetic behavior of the crystal was also explored using a vibrating sample magnetometer.     

Structural, optical and dielectric studies of glycinium trifluoroacetate single crystal

An organic material glycinium trifluoroacetate (GTFA) has been re-synthesized and large single crystals have been grown by solution technique. Complete structure of GTFA has been redetermined from single crystal XRD data. FTIR confirmed the presence of various functional groups. Melting point (152.44 °C), thermal stability and specific heat were studied from TG/ DTA and DSC. In UV absorption spectra, a lower cutoff value as 220 nm and a wide band gap as 4.86 eV for GTFA were observed. The dielectric studies, dielectric constant and loss were measured at different temperatures (30-90 °C) in the frequency range 100 Hz-2 MHz.     

Growth,structural, thermal,optical, dielectric,mechanical and laser damage threshold studies of nicotinium tartrate single crystals

An organic nonlinear optical nicotinium tartrate (NT) single crystal was grown by slow evaporation solution growth technique. The cell parameters of NT crystal were confirmed by single crystal and powder X-ray diffraction studies. The crystalline perfection of NT crystal was examined from HRXRD studies. The presence of functional groups was identified from FTIR spectral analysis. TGA and DSC studies revealed the thermal stability of NT crystal. UV–vis-NIR spectral studies showed that the NT crystal has wide transmission window in the entire visible region. The dielectric study on NT crystal established the normal dielectric behavior. The mechanical strength of NT crystal was studied by Vickers’ microhardness test. The laser damage threshold value of NT crystal was measured using Nd:YAG laser. The relative SHG efficiency of NT was measured to be 1.1 times that of KDP.     

Synthesis,spectral, thermal,optical and dielectric studies on 4-dimethylaminopyridinium picrate crystals

Single crystal of 4-dimethylaminopyridinium picrate was grown by slow evaporation solution growth method. The optical properties of the crystal were studied by using UV–vis absorption and transmittance studies. The emission spectrum indicates that the crystal shows green and red fluorescence emissions. The band gap energy of the crystal was calculated and it is found to be 2.05 eV. The thermal stability of the crystal was studied using thermogravimetry-differential thermal (TG-DTA) analyses. The thermal anomalies observed in the differential scanning calorimetry (DSC) heating and cooling cycles indicate the occurrence of a first order phase transition. FTIR spectrum was used to confirm the presence of various functional groups in the crystal. The synthesized crystal shows SHG efficiency 32 times greater than that of potassium dihydrogen phosphate (KDP). The dielectric constant and dielectric loss of the crystal decreases with increases in frequency.     

Role of copper ions in dielectric and structural investigations of lead– borate glasses

Glasses in the system 0.1CuO-(x-0.1)PbO-(1-x)B₂O₃ (0.3≤ x ≤ 0.7) were synthesized by using the melt quench technique. A number of studies such as X-ray diffraction (XRD), differential scanning calorimetry (DSC), fourier-transform infrared (FTIR) and Raman spectroscopy, electron paramagnetic resonance (EPR) and dielectric properties (viz., dielectric constant ??, dielectric loss and ac conductivity σ_ac) are employed to characterize the glasses. The amorphous nature of the glasses was confirmed using XRD while the glass transition temperature (T_g) of glass samples have been estimated from DSC investigation and found that the T_g decreases with increasing PbO content. Raman and FTIR spectroscopy reveals that when increasing lead ions, the tetrahedral [BO₄] units are gradually replaced by trigonal [BO₃] units. The EPR study leads to determine the local site of Cu²⁺ ions and its transformation with the Pb content in the studied glasses.     

Crystal growth and characterization of L-valine cadmium acetate a semiorganic NLO crystals

A new semiorganic nonlinear optical material, L-valine cadmium acetate, was grown successfully from aqueous solution by slow evaporation method. The grown crystals characterized by using Powder X-ray diffraction analysis confirms the structure of the grown title compound. The functional groups have been identified using FTIR spectral data. Transmittance compound was analyzed by using UV-vis spectrum. The thermal behavior of the grown crystal was determined with the aid of thermogravimetric analysis (TGA), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). The dielectric constant was studied as a function of frequency for various temperatures. The grown crystal has positive photoconductivity nature. The fluorescence spectrum of the crystal was recorded and its optical band gap is about 3.4479 eV. Second order nonlinear optical property of the grown crystal has been confirmed by modified Kurtz–Perry powder second harmonic generation (SHG) test.     

Dielectric and calorimetric studies on 1BC1EPOPB feroelectric liquid crystal having a large spontaneous polarization

Experimental investigations on the ferroelectric liquid crystal, R-4′(1-butoxycarbonyl-1-ethoxy) phenyl 4-(4-octyloxy phenyl) benzoate (1BC1EPOPB) of large spontaneous polarization (P _S(+) = 240?nC?cm^?2), using dielectric and calorimetric techniques, are reported. The temperature range of 25.0–125.0°C has been chosen for dielectric measurements. Dielectric dispersion studies are carried out in the temperature range 45.0–75.0°C and in the frequency range 2?Hz to 2?MHz for the smectic A, smectic C* and smectic X phases. A new phase called ‘smectic X’ has been found around 56.3°C. The transition temperatures identified by the dielectric dispersion studies for different phases and those given by DSC techniques are in close agreement.     

Dielectric,thermal and Raman spectroscopy studies of lead-free (Na0.5Bi0.5)1−xSrxTiO3 (x = 0, 0.04 and 0.06) ceramics

ABSTRACT

Lead-free (Na_0.5Bi_0.5)_1?xSr_xTiO₃ (x = 0, 0.04 and 0.06) ceramics with relative densities above 97% were prepared by solid-state synthesis process. Their dielectric, thermal and Raman properties were studied. X-ray diffraction analysis shows perovskite structure with rhombohedral symmetry at room temperature. Sr doping of Na_0.5Bi_0.5TiO₃ (NBT) results in an increase of the dielectric permittivity, diffusing of the permittivity maximum and its shift toward lower temperatures. The temperature of the rhombohedral–tetragonal phase transition indicated by the differential scanning calorimetry (DSC) peak and relaxational dielectric anomaly near the depolarization temperature are also shifted toward lower temperatures. The observed increase and broadening of the permittivity maximum, enhancement of the dielectric relaxation near the depolarization temperature, broadening of the DSC anomaly related to the rhombohedral–tetragonal phase transition and broadening of the Raman bands with increasing Sr content are attributed to the increase of the degree of cationic disorder and evident enhancement of the relaxor-like features in NBT–xST. This enhancement could play a positive role in the improvement of the piezoelectric performance of NBT-based ceramics.     

Thermal,Mechanical, and Dielectric Properties of a Dielectric Elastomer for Actuator Applications

Dielectric elastomers (DE) are a new type of electro-active material, which is able to produce a large degree of deformation under electrical stimulation. The thermal, mechanical, and dielectric properties of the most widely used dielectric acrylic elastomer (VHB 4910), commercially available from the company 3M, were studied by differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), dynamic mechanical analysis (DMA), and broadband dielectric spectroscopy (BDS) analyzer, respectively. DSC experiments on the VHB 4910 showed a glass transition at about ?40°C. VHB 4910 started to lose weight at about 250°C from the TGA study. The results of DMA indicated the storage modulus of VHB 4910 increased with frequency and had a strong temperature dependence of elasticity. The dielectric constant of VHB 4910 increased as a function of temperature up to 0°C, followed by a drop till 100°C. The mechanical and electrical efficiency of dielectric elastomer actuators (DEA) of VHB 4910 were analyzed. It was demonstrated that the actuation performance is dominated by the mechanical properties of the elastomer and is less influenced by the frequency and the temperature dependence of the dielectric properties; this may be used to guide the design of actuator configurations, as well as the choice of actuator materials.     

Growth of 4-(dimethylamino) benzaldehyde doped triglycine sulphate single crystals and its characterization

Single crystals of triglycine sulphate (TGS) doped with 1 mol% of 4-(dimethylamino) benzaldehyde (DB) have been grown from aqueous solution at ambient temperature by slow evaporation technique. The effect of dopant on the crystal growth and dielectric, pyroelectric and mechanical properties of TGS crystal have been investigated. X-ray powder diffraction pattern for pure and doped TGS was collected to determine the lattice parameters. FTIR spectra were employed to confirm the presence of 4-(dimethylamino) benzaldehyde in TGS crystal, qualitatively. The dielectric permittivity has been studied as a function of temperature by cooling the sample at a rate of 1 °C/min. An increase in the Curie temperature T_c=51 °C (for pure TGS, T_c=48.5 °C) and decrease in maximum permittivity has been observed for doped TGS when compared to pure TGS crystal. Pyroelectric studies on doped TGS were carried out to determine pyroelectric coefficient. The Vickers's hardness of the doped TGS crystals along (0 1 0) face is higher than that of pure TGS crystal for the same face. Domain patterns on b-cut plates were observed using scanning electron microscope. The low dielectric constant, higher pyroelectric coefficient and higher value of hardness suggest that doped TGS crystals could be a potential material for IR detectors.     

Synthesis, crystal structure, thermal and dielectric properties of bis(p-phenylenediammonium) chloride hexachlorobismuthate(III) monohydrate [C6H4(NH3)2]2ClBiCl6.H2O

Synthesis, crystal structure, and dielectric properties of [C₆H₄(NH₃)₂]₂ClBiCl₆.H₂O are reported. The compound crystallizes in the monoclinic system with space group P2₁/n. The unit cell dimensions are a = 9.836(5), b = 19.582(5), c = 13.082(5) ?, β = 104.731(5)° with Z = 4. The atomic arrangement can be described by an alternation of organic and inorganic layers. The anionic layer is built up of octahedral of [BiCl₆]^3- arranged in sandwich between the organic layers. The crystal packing is governed by means of the ionic N–H···Cl hydrogen bonds, forming a three-dimensional network. The dielectric properties have been investigated at temperature range from 297 to 410 K at various frequencies (10 Hz–100 kHz). Dielectric studies were performed to confirm results obtained with thermal analysis. The evolution of dielectric constant as a function of temperature and frequency of single crystal has been investigated in order to determine some related parameters.     

Oxygen-vacancy-related high-temperature dielectric relaxation and electrical conduction in 0.95K0.5Na0.5NbO3-0.05BaZrO3 ceramic

The crystal structure and dielectric properties of 0.95K_0.5Na_0.5NbO₃-0.05BaZrO₃ (KNN-BZ) ceramic have been investigated by X-ray diffraction and dielectric measurement. A rhombohedral distortion was caused and the dielectric permittivity near Curie temperature was significantly enhanced by introducing BZ into KNN. The dielectric and conductivity properties of the sample were studied by using AC impedance spectroscopy and universal dielectric relaxation law in detail. The typical high-temperature dielectric relaxation process was confirmed to be related to the oxygen vacancies inside the ceramic. The effect of lattice distortion on the activation energy for oxygen vacancy migration in KNN-BZ was discussed by comparing with KNN and KNN-BaTiO₃.     

Effect of urea and thiourea on nonlinear optical hippuric acid crystals

Pure, urea and thiourea doped hippuric acid (HA) single crystals have been grown in acetone using slow evaporation technique at a constant temperature, with the vision to improve the properties of the crystals. The crystal systems and the unit cell parameters of the grown crystals were identified from single crystal X-ray diffraction. The crystalline nature of the grown crystals was confirmed by powder X-ray diffraction and the diffraction peaks were indexed. The variations in composition due to the addition of dopants were identified by CHNS analysis. FT-IR studies reveal the presence of different vibrational bands. The optical characteristics were assessed by UV–vis analysis and it indicates the transmission in the visible region. TGA and DSC studies indicate the thermal behavior of pure and doped crystals. The Second Harmonic Generation (SHG) has been tested using Kurtz Powder Technique for the pure and doped crystals. It is found that the thiourea doped hippuric acid crystals have SHG efficiency of 2.08 times higher than that of potassium dihydrogen phosphate (KDP) single crystal. The dielectric studies were carried out, and the variations of dielectric constant and dielectric loss with temperature have been studied.     

2-Phenylethylammonium p-hydroxybenzoate: Growth,structural, spectral,thermal, optical and mechanical characterization

An efficient nonlinear optical single crystal of 2-phenylethylammonium p-hydroxybenzoate (2PPHB) was grown from aqueous solution by slow evaporation solution growth method. Single crystal X-ray diffraction studies confirmed that 2PPHB crystallizes in orthorhombic crystal system with non-centrosymmetric space group of Pna2₁. The presence of functional groups in the synthesized compound was identified by FTIR spectral analysis. The grown crystals were thermally stable up to 155 °C. UV–vis absorption, photoluminescence and birefringence optical properties of grown crystal were explored. The laser induced surface damage threshold and relative second harmonic generation properties of the grown crystal were studied using Q-switched Nd:YAG laser. The variation of dielectric properties of the grown crystal with frequency was investigated for different temperatures. The mechanical response of the crystal was studied by Vicker's microhardness technique.     

Structural phase transition,ionic conductivity,and dielectric investigations in K3H(SO4)2 single crystals

Optical observation, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) measurements have been carried out on K₃H(SO₄)₂ crystal in the temperature range between 25 and 300 °C. Domain structures of K₃H(SO₄)₂ were observed at room temperature which are the same as those observed in other member of A₃H(XO₄)₂ which show ferroelasticity. Two endothermic peaks of DSC were found at around 206 and 269 °C. In this temperature range, the result of TGA indicate the loss of weight. It supports that partial dehydration is most probable. The first peak can be accounted for the dehydration reaction on the surface of crystals, and the second peak corresponds to the melting of the sample crystal. The impedance measurements were performed as a function of both temperature and frequency. The electrical conductivity increases with increasing temperature and the sample crystal becomes a fast ionic conductor at the temperatures above 206 °C. The high conductivity of the crystal is caused by the increases of the defects due to the dehydration. The dielectric properties of the sample crystal were studied by the impedance spectroscopy.     

Design and optimization of 2D photonic crystal waveguides based on silicon

The existence and properties of photonic band gaps was investigated for a square lattice of dielectric cylinders in air. Band structure calculations were performed using the transfer matrix method as function of the dielectric constant of the cylinders and the cylinder radius-to-pitch ratio r/a. It was found that band gaps exist only for transverse magnetic polarization for a dielectric contrast larger then 3.8 (index contrast >1.95). The optimum r/a ratio is 0.25 for the smallest index contrast. For silicon cylinders (n = 3.45) the widest gap is observed for r/a = 0.18. Band structure calculations as function of r/a show that up to four gaps open for the silicon structure. The effective index was obtained from the band structure calculations and compared with Maxwell–Garnett effective medium theory. Using the band structure calculations we obtained design parameters for silicon based photonic crystal waveguides. The possibility and limitations of amorphous silicon, silicon germanium and silicon-on-insulator structures to achieve index guiding in the third dimension is discussed.