Growth, optical, mechanical and dielectric studies on NLO active pure and metal ion doped single crystals of bis-thiourea zinc chloride

Good quality single crystals of pure and metal ion (Ni²⁺) doped bis-thiourea zinc chloride (BTZC) possessing excellent nonlinear optical properties have been grown from aqueous solution by the slow solvent evaporation technique. The lattice parameters of the grown crystals are determined by single crystal X-ray analysis. The well defined sharp peaks in the powder X-ray diffraction pattern reveals the crystalline perfection and the EDAX spectrum confirms the presence of dopant in the lattice of the parent crystal. The DRS UV-visible spectral study reveals improved transparency for the doped crystal, ascertaining the inclusion of metal ion in the lattice. The optical band gap of the pure and doped crystals was calculated to be 4.8 and 5.2 eV respectively from the UV transmission spectrum. The vickers hardness test brings forth higher hardness value for Ni²⁺doped BTZC as compared to pure BTZC crystal. The dielectric measurement exhibits very low dielectric constant and dielectric loss at higher frequencies for both the pure and Ni²⁺doped BTZC. The existence of second harmonic generation signals in the crystal also has been confirmed by performing the Kurtz powder test.     

Synthesis,growth and characterization of l-threonine zinc acetate (LTZA) NLO single crystal

Single crystals of l-threonine zinc acetate (LTZA) were grown from an aqueous solution by slow evaporation technique. Single crystal X-ray diffraction analysis reveals that the crystal belongs to monoclinic system. The optical transmission study reveals the transparency of the crystal in the entire visible region and the cut off wavelength has been found to be 350 nm. The optical band gap is found to be 3.55 eV. The microhardness studies reveal the mechanical strength of the grown crystal. The dielectric constant and dielectric loss were carried out for the grown crystal. Photoconductivity measurements carried out on the grown crystal reveal the negative photoconducting nature.     

Thermal and dielectric studies of nickel malonate dihydrate single crystals

Single crystals of nickel malonate dihydrate were grown by the gel technique, employing the single diffusion method. Thermal dehydration of the crystal was investigated by thermogravimetric and differential thermal analyses. The title compound exhibits a steady thermal behaviour at higher temperature range of 350-800 °C. The dielectric properties of the prepared sample were analyzed as a function of frequency in the range of 1 kHz-1 MHz and at temperatures between 40 and 140 °C.     

Growth aspects,spectral, thermal and hardness studies of rare earth cerium(III)nitrate doped zinc(tris) thiourea sulphate single crystals

Single crystals of pure and cerium(III)nitrate doped zinc(tris) thiourea sulphate (ZTS) were grown from aqueous solution by slow evaporation method. The cell parameters of the grown crystals were determined by single crystal X-ray diffraction analysis. Powder X-ray diffraction patterns were recorded and indexed for the structural confirmation. The presence of functional group in the compound has been confirmed by FTIR analysis. UV–vis absorption spectrum has been recorded to determine the cut-off wavelength of the crystal. TGA/DTA studies show thermal stability of the grown crystals. SEM-EDX analysis revealed the incorporation of the impurity (Ce³⁺) into ZTS crystals. The microhardness study reveals that the hardness number (H_v) increases with load for all the grown crystals of this work. From the values of work hardening coefficients, it was concluded that pure and cerium nitrate doped ZTS crystals belong to the category of soft materials. The second harmonic generation of cerium(III)nitrate doped ZTS crystals was confirmed by Kurtz–Perry powder method using Nd:YAG laser.     

Optical,dielectric and ferroelectric behaviour on doped lithium sulphate crystals

Optically transparent single crystals of urea doped with lithium sulphate (ULS), thiourea doped with lithium sulphate (TLS) and cupric chloride doped with lithium sulphate (CuLS) were grown in aqueous solution by slow evaporation technique at room temperature. Single crystal X-ray diffraction analysis confirmed the changes in the lattice parameters of the ULS, TLS and CuLS. The lattice parameters and the quality of doped crystals were confirmed by powder X-ray diffraction studies. The functional groups present in the ULS, TLS and CuLS crystals were determined qualitatively by using Fourier transform infrared (FTIR) spectroscopy. Optical absorption studies revealed that doped crystals acquire very low absorption in the entire visible region. The energy dispersive X-ray analysis (EDAX) gives the chemical composition of the grown crystal. CHN analysis confirmed the presence of carbon, hydrogen and nitrogen in the added dopants. The dielectric constant and dielectric loss of the doped crystal were studied as a function of frequency and temperature and the ferroelectric property of the crystal was confirmed by dielectric studies.     

EPR and optical studies of Cu doped ammonium dihydrogen phosphate single crystals

Electron paramagnetic resonance (EPR) spectra of Cu²⁺ ion in ammonium dihydrogen phosphate are studied at liquid nitrogen temperature (77 K). Four magnetically inequivalent Cu²⁺ sites in the lattice are identified. The angular variation spectra of the crystal in the three orthogonal planes indicate that the paramagnetic impurity, Cu²⁺ enters the lattice substitutionally in place of NH₄⁺ ions. The spin Hamiltonian parameters are determined with the fitting of spectra to rhombic symmetry crystalline field. The ground state wave function of Cu²⁺ ion is constructed and found to be predominantly |x²-y²〉. The cubic field parameter (Dq) and tetragonal parameters (Ds and Dt) are determined from optical spectra at room temperature. By correlating EPR and optical absorption spectra, the bonding coefficients are calculated and nature of bonding of metal ion with different ligands in the crystal is discussed.     

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.     

Spectral,NLO, thermal,hardness and SEM studies of phosphate doped bis-urea oxalic acid crystals for laser applications

Phosphate doped bis-urea oxalic acid (PBUO) crystals were grown using the aqueous solution by slow evaporation technique. Single crystal XRD study indicates that the sample crystallizes in monoclinic structure. The mechanical parameters like hardness, yield strength and stiffness constant of the crystal were determined by using the Vickers hardness tester. UV-visible spectral studies were done to determine the various linear optical parameters. Second harmonic generation (SHG) efficiency was measured for the grown crystal of PBUO to understand the nonlinear optical activity. TG/DTA analysis shows that the PBUO crystal is thermally stable upto 170 °C. Energy dispersive X-ray analysis (EDAX) was carried out by recording the EDAX spectrum of the grown crystal to identify elements in the sample. The grown PBUO crystals were also characterized by FTIR, SEM, PL, LDT and impedance studies.     

Studies on growth,structural, optical and mechanical properties of xylenol orange dye admixtured l-arginine phosphate single crystal

Bulk single crystals of pure and xylenol orange (XO) admixtured l-arginine phosphate (LAP) were grown by slow cooling technique. The cell parameters and crystallinity of pure and dye admixtured LAP crystals were confirmed by single crystal and powder X-ray diffraction analyses. HRXRD analysis reveals the presence of xylenol orange dye in interstitial site of LAP crystal lattice and it confirms the crystalline perfection of grown crystals. The functional groups of grown crystals were confirmed by FTIR spectral analysis. UV–vis transmission studies show the characteristic absorption of xylenol orange admixtured LAP crystal. Vickers’ microhardness and laser damage threshold studies were carried out on these crystals. Kurtz and Perry powder test was conducted to measure the second harmonic generation efficiency of pure and dye admixtured LAP crystals.     

Photoconductivity, dielectric and thermal investigations of pure, benzophenone- and iodine-doped benzoyl glycine NLO single crystals

Physical properties such as photoconductivity, dielectric and thermal stability have been investigated for pure benzoyl glycine (BG) crystals. In addition to this, the influence of dopants (benzophenone and iodine) of these properties on BG crystals has been studied. Photoconductivity studies on pure BG, benzophenone-and iodine-doped BG revealed the positive photoconducting nature. The dielectric responses of the samples have been studied in the frequency range 100 Hz-500 KHz at room temperature and the results are discussed in detail. The thermogravimetric studies of pure and doped BG crystals indicate that the presence of dopants has slightly increased the decomposition temperature of pure BG samples, thereby enhancing thermal stability to the doped ones.     

Growth and characterization of pure and doped organic nonlinear optical single crystal: l-Alanine alaninium nitrate (LAAN)

The pure l-alanine alaninium nitrate (LAAN) single crystals and LAAN crystals doped with lanthanum oxide (La₂O₃), sodium chloride (NaCl), urea (CH₄N₂O), glycine (C₂H₅NO₂) and thiourea (CH₄N₂S) were grown by slow evaporation method. The X-ray diffraction analysis, scanning electron microscopy (SEM), energy dispersive X-ray (EDAX) analysis, UV–vis spectral analysis, dielectric studies and powder SHG measurement are studied systematically. The slight changes in the lattice parameters were observed for the doped crystals compared to pure LAAN crystal. The incorporation of doping into the crystal lattice was confirmed by energy dispersive X-ray analysis. There is no change in the transmission window due to doping and the percentage of transmission in doped samples was found to increase as compared to that of pure LAAN crystal. The dielectric constant of pure crystal was found to be less than that of doped crystals. The AC conductivity was found to increase after doping and with the increase in temperature. A green radiation of 532 nm was observed from the pure and doped LAAN crystals confirming the second harmonic generation (SHG) of the crystals.     

Magnetic and dielectric studies of nanocrystalline zinc substituted Cu-Mn ferrites

Ferrites with the general formula Cu_1−xZn_xFeMnO₄ (where 0≤x≤1) were prepared through a citrate gel auto-combustion route. Structural characterizations carried out by X-ray diffraction reveal that the lattice constant increases with increase in zinc content. Transmission electron microscopic measurements confirm the nanoscale nature of the particles. Room temperature saturation magnetization was measured as a function of zinc concentration. The saturation magnetization increases up to x=0.25 and then decreases as zinc concentration increases. Dielectric permittivity, dielectric loss tangent, ac conductivity and complex dielectric impedance were studied in the frequency range 20 Hz-1 MHz. The results indicated a usual dielectric dispersion due to the Maxwell-Wagner type of interfacial polarization. Dielectric loss showed similar behavior as dielectric permittivity. The ac conductivity increased linearly with frequency. Complex impedance spectroscopic studies confirmed that conduction in the samples is via grain boundaries. In general, substitution of zinc plays an important role in changing the structural, electrical and magnetic properties of these ferrites.     

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,crystal growth and characterization of organic NLO material: 4-Bromo-4′-hydroxybenzylidene aniline

One of the novel benzylidene aniline derivatives, 4-bromo-4′-hydroxybenzylidene aniline (BHBA) was synthesized and single crystal of BHBA was grown from solution following slow evaporation method at room temperature. Unit cell parameters of the grown crystal were determined from single crystal X-ray diffraction studies. Functional groups of BHBA were identified from Fourier transform infrared spectral study. UV–vis-NIR analysis of BHBA showed that the crystal is transparent between wavelengths 400 and 1100 nm. Thermal stability of the title compound was examined by thermogravimetric and differential scanning calorimetric studies. Fluorescence spectrum of the grown crystal recorded using spectrofluorometer shows emission peak at 450 nm. The second harmonic generation efficiency of BHBA estimated by Nd:YAG pulsed laser employing the Kurtz powder technique is ∼1.3 times that of potassium dihydrogen orthophosphate. Microhardness studies reveal that BHBA possesses high Vickers hardness value. The dielectric measurements were carried out at different temperatures and frequencies and the results are discussed.     

Influence of l-alanine doping on crystalline perfection, SHG efficiency, optical and mechanical properties of KDP single crystals

Pure and l-alanine (LA) doped single crystals of potassium dihydrogen orthophosphate (KDP) were grown by slow evaporation solution technique (SEST) in aqueous solution at ambient temperature. Powder X-ray diffraction study was done to confirm the crystal system and lattice parameters of KDP. No additional phases were observed at all doping concentrations (1-7.5 mol%), which was further confirmed by FT-Raman spectroscopy analysis. The influence of LA doping on the crystalline perfection was assessed by high-resolution X-ray diffractometry (HRXRD) analysis. HRXRD studies revealed that the grown crystals could accommodate LA at the interstitial positions in the crystalline matrix of KDP up to some critical concentration without any deterioration in the crystalline perfection. Above this concentration, very low angle structural grain boundaries were developed and it seems that the excess LA above the critical concentration was segregated along the grain boundaries. The SHG efficiency was measured using the Kurtz powder technique. The relative SHG efficiency of the crystals was found to be increased with doping concentration up to 5 mol% and above this it decreases. Optical transmission study also revealed the same behavior with enhancement up to 5 mol% concentration and later decreased. The hardness values were found to be increased by increasing the doping concentration.     

Electrical and nonlinear optical studies of flux grown Mo and Fe doped KTP crystals

The molybdenum (Mo) and ferric (Fe) doped potassium titanyl phosphate (KTP) crystals were grown by high temperature solution growth (HTSG) technique. The concentration of Mo and Fe in grown crystals was measured by EDX analysis. The SHG efficiencies of the Mo and Fe doped KTP crystals were measured and it was found to be 1.77 and 1.38 times respectively higher than that of pure KTP crystal. The frequency dependence of dielectric constant, loss and ac conductivity was studied at room temperature. The phase matching measurements were made using a Q-switched Nd:YAG laser operating at 1064 nm and the measured phase matching angles are 44.2° and 87.88° for Mo and Fe doped KTP crystals respectively.     

Growth and comparison of physicochemical properties of pure,Ca and Sr doped NH4Sb3F10 single crystals for electro optic applications

Single crystals of pure, Ca²⁺ and Sr²⁺ doped NH₄Sb₃F₁₀ are grown by slow evaporation technique. The effect of dopants on the growth and physicochemical properties also have been investigated and reported for the first time. The grown crystals are characterized with the aid of single crystal X-ray diffractometry to confirm the crystal structure. EDAX studies are done to confirm the presence of dopants in the crystal lattice. The vibrational frequencies of various group ligands in the crystals have been derived from the Fourier transform infrared (FT-IR) spectrum. From the optical absorption spectrum the band gap energy was calculated and it was found to be 5.76, 6.29 and 6.35 eV for pure, Ca²⁺ and Sr²⁺ doped NH₄Sb₃F₁₀ crystals respectively. Thermal stability of the sample has been analysed using TG-DTA analysis. The activation energy of pure, Ca²⁺ and Sr²⁺ doped NH₄Sb₃F₁₀ crystals were calculated from the dc conductivity measurements and it is found to be 0.2728, 0.2816 and 0.3622 eV Experimental results shows improved physicochemical properties when the dopant is added to the pure material.     

Synthesis, magnetic and dielectric properties of Er-Ni doped Sr-hexaferrite nanomaterials for applications in High density recording media and microwave devices

A sol-gel combustion method has been successfully employed for the synthesis of Sr-hexaferrite nanomaterials doped with Er³⁺ and Ni²⁺ at strontium and iron sites, respectively. The X-ray diffraction analysis confirmed the single magnetoplumbite phase and the crystallite size was found to be in the range of 14-16 nm, suitable for obtaining signal-to-noise ratio in the high density recording media. The magnetic properties such as saturation magnetization (M_s), remanence (M_r) and coercivity (H_c) were calculated from hysteresis loops. M_s, M_r and H_c are observed to increase with the Er-Ni content. The dielectric constant (ε´) and dielectric loss (tan δ) is found to decrease with the increase in frequency and is explained on the basis of Maxwell-Wagner and Koops theory. The decrease in dielectric constant and dielectric loss but increase in saturation magnetization and remanence with Er-Ni content suggests that the materials are suitable for applications in microwave devices and high density recording media .     

Growth,optical and dielectric studies of tyrosine-doped glycine

Single crystals of tyrosine-doped glycine (TRG) were successfully grown by slow evaporation technique at room temperature. Crystals of TRG were obtained in a period of 30 days. X-ray diffraction (XRD) analysis reveals that the crystal belongs to monoclinic system with non-centrosymmetric space group of p21. The presence of functional groups was estimated by Fourier transform infra-red (FTIR) analysis. The optical cut-off wavelength for this crystal was observed by UV–vis absorbance spectra. Electrical measurements (dielectric, AC conductivity) were carried out at temperatures 40, 80, and 120 °C. The results indicate that the values of dielectric constant and dielectric loss are less at higher frequencies.