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.     

Growth and Characterization of Organic NLO Crystal:β-Naphthol

Single crystals of β-Naphthol(βN),an organic nonlinear optical(NLO) material was successfully grown by temperature lowering method using chloroform as solvent.The initial compound was purified by repeated recrystallization process.As-grown crystals were characterized by single crystal X-ray diffraction(XRD) studies to ascertain that βN crystal crystallized in the monoclinic system with a noncemtrosymmetric space group.Vibrational frequencies of various functional groups in the crystals were derived from Fourier transform infrared(FTIR) spectroscopy and proton nuclear magnetic resonance(NMR) spectrum.Optical characterization was done using UV-Visible near-infrared(NIR) spectroscopy.The thermal behaviour of the material was studied by thermo gravimetric and differential thermal plots.Scanning electron microscopy(SEM) study was carried out on the surface of the grown crystals to investigate the nature of defects in the crystal surface and the NLO property of the crystal was tested by Nd:YAG laser as a source.     

Effect of Sodium Metasilicate on Structural,Optical,Dielectric and Mechanical Properties of ADP Crystal

For the first time,sodium metasilicate(SMS) doped ammonium dihydrogen phosphate(ADP) crystal was grown by slow evaporation solution technique. The unit cell parameters of grown crystal were determined by means of single crystal X-ray diffraction technique. The qualitative analysis of SMS doped ADP crystal was carried out using energy dispersive X-ray and Fourier transform infrared analysis. The increase in optical transparency of doped ADP crystal was ascertained in the range of 200–900 nm using the UV-visible spectral analysis. The vital optical constants were evaluated using the transmittance data to explore various optical device applications of crystal. The assertive influence of SMS on mechanical and dielectric behavior of ADP crystal was investigated by means of Vickers microhardness analysis and dielectric studies,respectively. The enhancement in second harmonic generation(SHG) efficiency of SMS doped ADP crystal with reference to potassium dihydrogen phosphate(KDP) and ADP was confirmed from Kurtz–Perry SHG test. The Kerr lensing nonlinearity in SMS doped ADP crystal was identified by means of Z-scan analysis and the third order nonlinear optical susceptibility(χ~3) was found to be6.19×10~(-5)esu,which vitalizes its application for laser stabilization systems.     

Growth, Structural and Microhardness Studies on New Semiorganic Single Crystals of Calcium Para Nitrophenolate Dihydrate

Good quality crystals of calcium p-nitrophenolate （NPCa） were grown from saturated solution by slow evaporation method. The crystal structure analysis and the molecular arrangement of these crystals were determined using X-ray diffraction （XRD）. From Single crystal XRD studies, NPCa is found to be crystallized in the mon- oclinic system with a space group P21/n. The functional groups of the material were confirmed qualitatively by F-FIR （Fourier transform infrared spectroscopy） spectral analysis. Optical absorption studies reveal the absorption region and microhardness studies were carried out to confirm the mechanical behaviour of the crystals.     

Analysis of Dielectric and Electro-optic Responses of Nanomaterials Doped Ferroelectric Liquid Crystal Mixture

Dielectric and rotational viscosity measurements of a multi-component ferroelectric liquid crystal mixture were performed by adding a small concentration (0.01 wt%) of silica and multi walled carbon nanotubes (MWCNTs). Liquid crystals turn out to be outstanding hosts for nanomaterials. A remarkable increase in the rotational viscosity was noticed in CNT doped system as compared to silica doped same liquid crystal system. Comparison of dielectric studies shows higher value of permittivity and dielectric losses for silica-doped sample than those of CNT doped sample. The results have been interpreted both experimentally and theoretically.     

A Comparison between TGT and Cz Grown Nd：YAG

Large sized neodymium-doped Y3Al5O12 （Nd：YAG） laser crystals have been grown by temperature gradient technique （TGT） method and compared with Czochralski （Cz） method. The comparison of these two crystal growth methods has been listed. The results showed that the TGT method has many advantages over the Cz method. The concentration distribution of Nd ions in the crystals was determined and the absorption spectra of these crystals have been investigated and compared. The TGT grown highly doped Nd：YAG crystal has a larger absorption FWHM than that of Cz grown Nd：YAG crysral. Highly doped Nd：YAG （～2.8 at. pct） crystals could be obtained by TGT.     

Sensitivity to Combustible Gas for ZnO Thin Films

A fine polycrystalline ZnO thin film with 0.3～0.6 μm grain size was obtained by sol-gel process and a consequential heat treatment at 500℃. The process of preparing ZnO thin film was analysed. The sensitivity and conductivity of ZnO thin films as combustible gas (CO, CH4,H2) sensor as well as the influence of catalyst and pH value of the precursor on its sensitivity were studied in detail. The structure characteristics of ZnO thin film by different process were irlvestigated by X-ray diffraction, thermal analysis and photoelectron spectrometer. The atomic ratio of Zn to O on the surface of ZnO thin film was found to be 1.14:1 measured from XPS result. The conductivity of the thin film increases greatly when doped with Al3+ ion but decreases while doped with Na+ ion     

Preparation and Gas-sensing Characteristics of Na~+-doped ZnO Single Crystals

ZnO single crystals were grown by vapor phase reaction of Zno powder with active carbon powdei at an elevated temperature The typical crystals were colorless and transparent with maximum size o4 0.1 mm in diameter and 25 mm in length, The gas-sensing characteristics of Na+-doped anc undoped single crystals were investigated in 1 %H2. Co and CH, in air between 1 50 and 600℃. It was found that the undoped ZnO single crystals showed little gas sensitivity in air. and Na+-doping can greatly enhance the senstivity by increasing the resistivities. The maximum sensitivity of the samples is 22 (Ra/ Rg) for H2. 1 2 for CO and 4 for CH4     

Optical Spectra and Gain Properties of Ho3＋/Pr3＋ Co-doped LiYF4 Crystal

The LiYF4 single crystals singly doped Ho3＋ and co-doped Ho3＋, Pr3＋ ions were grown by a modified Bridgman method. The Judd-Ofelt strength parameters （Ω2, Ω4, Ω6） of No3＋ were calculated according to the absorption spectra and the Judd-Ofelt theory, by which the radiative transition probabilities （A）, fluorescence branching ratios （β） and radiative lifetime （τ rad） were obtained. The radiative lifetimes of 5/6 and 5/7 levels in Ho3＋ （1 mol%）：LiYF4 are 10.89 and 20.19 ms, respectively, while 9.77 and 18.50 ms in Ho3＋/pr3＋ doped crystals. Hence, the τ rad of 5/7 level decreases significantly by introduction of Pr3＋ into Ho3＋：LiYF4 crystal which is beneficial to the emission of 2.9 μm. The maximum emission cross section of Ho3＋：LiYF4 crystal located at 2.05 μm calculated by McCumber theory is 0.51 ×10-20 cm2 which is compared with other crystals. The maximum emission cross section at 2948 nm in Ho3＋/pr3＋ co-doped LiYF4 crystal obtained by Fuchtbauer- Ladenburg theory is 0.68 × 10-20 cm2, and is larger than the value of 0.53 × 10-20 cm2 in Ho3＋ singly doped LiYF4 crystal. Based on the absorption and emission cross section spectra, the gain cross section spectra were calculated. In the Ho3- ions singly doped LiYF4 crystal, the gain cross sections for 2.05 μm infrared emission becomes positive once the population inversion level reaches 30%. It means that the pump threshold for obtaining 2.05 μm laser is probably lower which is an advantage for Ho3＋-doped LiYF4 2.05 μm infrared lasers. The calculated gain cross section for 2.9 μm mid-infrared emission does not become positive until the population inversion level reaches 40% in Ho3＋/pr3＋：LiYF4 crystal, but 50% in Ho3＋ singly doped LiYF4 crystal, indicating that a low pumping threshold is achieved for the H03＋：5/6 → 5/7 laser operation with the introduction of Pr3＋ ions. It was also demonstrated that Pr3＋ ion can deplete rapidly the lower laser Ho3＋：5/7 level and has influence on t     

Growth and Solvent Effects of a Promising Nonlinear Optical Sodium Paranitrophenolate Dihydrate (NO_2-C_H_4-ONa·2H_2O) Single Crystal

Sodium paranitrophenolate dihydrate (NPNa·2H2O) is an excellent semiorganic nonlinear optical (NLO) material, crystallizes both in water and methanol with high degree of transparency. Good optical quality single crystals of dimension upto 18 mm×6 mm×3 mm are obtained by isothermal solvent evaporation technique. The solubility of the crystal in different solvents was measured gravimetrically. The single crystals of NPNa·2H2O show variation in physical properties and growth rate in different solvents. Methanol or ethanol solution yields crystals of bipyramidal shape with clear morphology. However, methanol grown crystal is exhibiting improved hardness parameters and possesses excellent thermal stability as compared to water grown crystals. The effects of solvent on hardness parameter along with thermal and optical properties of NPNa·2H2O was revealed in this paper.     

Growth of Hydroxyapatite Crystal in the Presence of Origanic Film

The growth of hydroxyapatite (HAp) crystal in the presence of hexadecylamine was investigated. Due to its high polarity and high charge density, the organic film could increase the ion supersaturation on its surface. Therefore the growth of pure HAp crystals was accelerated. Moreover, the positive headgroups of the organic film could act as recognized nucleation sites and orient the growth of HAp crystals along the <0001> direction.     

Synthesis of Single-Crystal TiO2 Nanowire Using Titanium Monoxide Powder by Thermal Evaporation

TiO 2 nanowires were synthesized successfully in a large quantity by thermal evaporation using titanium monoxide powder as precursor. X-ray diffraction results showed that all the products were pure rutile phase of TiO 2 . According to microstructural observations, the nanowires have two typical morphologies, a long straight type and a short tortuous type. The straight nanowires were obtained at a wide temperature range of 900-1050 ℃, while the tortuous ones were formed below 900 ℃. Transmission electron microscopy characterization revealed that both the straight and the tortuous nanowires are single-crystal rutile TiO 2 . The preferential growth direction of the nanowires was determined as [110] orientation according to electron diffraction and high-resolution image analyses. The morphological change of TiO 2 nanowires was discussed by considering the different atomic diffusion rates of Ti atoms caused by the phase transformation in Ti substrate at around 900 ℃.     

Synthesis of High Purity SiC Powder for High-resistivity SiC Single Crystals Growth

High purity silicon carbide （SIC） powder was synthesized in-situ by chemical reaction between silicon and carbon powder. In order to ensure that the impurity concentration of the resulting SiC powder is suitable for high-resistivity SiC single crystal growth, the preparation technology of SiC powder is different from that of SiC ceramic. The influence of the shape and size of carbon particles on the morphology and phase composition of the obtained SiC powder were discussed. The phase composition and morphology of the products were investigated by X-ray diffraction, Raman microspectroscopy and scanning electron microscopy. The results show that the composition of resulting SiC by in-situ synthesis from Si/C mixture strongly depends on the nature of the carbon source, which corresponds to the particle size and shape, as well as the preparation temperature. In the experimental conditions, flake graphite is more suitable for the synthesis of SiC powder than activated carbon because of its relatively smaller particle size and flake shape, which make the conversion more complete. The major phase composition of the full conversion products is β-SiC, with traces of α-SiC. Glow discharge mass spectroscopy measurements indicated that SiC powder synthesized with this chemical reaction method can meet the purity demand for the growth of high-resistivity SiC single crystals.     

High pressure floating-zone growth and property characterization of Cr-doped hexagonal YMnO_3 crystals

Large crystal growth of Cr-doped h-YMnO_3 has been investigated by using a high pressure optical floatingzone method. The size of the grown crystals is typically 60–70 mm in length and 4–5 mm in diameter. The structure of the grown crystals is analyzed by powder X-ray diffraction and scanning electron microscopy.The defects in the as-grown crystals, including low-angle grain boundary and inclusions are studied. An off-stoichiometric phenomenon is found with a slight Cr deficiency in different parts. The relationship between defects and growth conditions during crystal growth is also discussed. The magnetic properties show spin-glass phase features with weak ferromagnetic behavior below 30 K.     

Growth of LaBr_3:Ce～(3+) Single Crystal by Vertical Bridgman Process in Nonvacuum Atmosphere

The growth of LaBr3:Ce3+ crystal by the vertical Bridgman process in a nonvacuum atmosphere was reported. According to the dehydration procedure of LaBr3·7H2O and CeBr3·7H2O investigated by differential thermal analysis/thermogravimetry (DTA/TG), anhydrous LaBr3 and CeBr3 were prepared by heating LaBr3·7H2O and CeBr3·7H2O at 240–260°C for 5–6 h in dried HBr atmosphere. Using the feed materials prepared from the anhydrous lanthanon bromides, a 0.5 mole fraction Ce3+ doped LaBr3 crystal with size of φ25 mm×50...     

Effective Increase of Crystal Area during Sublimation Growth of 6H-SiC by Using the Cone-shaped Baffle

A novel design of crucible is proposed in this paper for the growth of SiC crystals. The relation between grown crystal shape and temperature distribution in a growth chamber was discussed. It is pointed out that the crystal shape had a close relationship with temperature distribution. The calculations suggested that the radial temperature field of the growing crystal became homogenous by setting up the cone-shaped baffle in the growth chamber. By modifying the crucible design and temperature distribution in the growth chamber, it is possible to enhance the enlargement of crystal, and also possible to keep grown surface flat.     

Electrical, Thermal, Photocatalytic and Antibacterial Studies of Metallic Oxide Nanocomposite Doped Polyaniline

ZnOe-ZrO2 nanocomposite was prepared by sole gel method and in-situ polymerization was used to synthesize ZnOe-ZrO2 nanocomposite doped polyaniline(PANI).The materials were characterized by X-ray diffraction(XRD),Fourier transform infrared(FTIR) spectroscopy,transmission electron microscopy(TEM),scanning electron microscopy(SEM) and energy dispersive X-ray spectroscopy(EDX) to ensure the crystallite size,functional groups,morphology and chemical composition of the polymer nanocomposite complex.The average particle size of the ZnOe-ZrO2 nanoparticles was found to be 20.5 nm.Thermal gravimetric analysis(TGA) was used to study the thermal stability of the complex,shows improved thermal stability of polymer nanocomposite as compared to the pure organic polymer.The material also possesses good electrical conductivity.Additionally,the photocatalytic activity of the materials was investigated by monitoring the decolorization of Acid Blue 29 dye in a UV photocatalytic reactor and PANI-ZnOe-ZrO2 was found to possess higher photocatalytic activity than pure PANI.Finally,the antibacterial activity of the materials was examined and it was observed that PANI-ZnOe-ZrO2 could be used as an excellent antibacterial agent.Hence,desired properties could be integrated by mixing appropriate phases of the materials for specific applications such as heterogeneous catalyst,antibacterial agents,antibiotics delivery and high temperature conducting polymers.     

Solvothermal Synthesis of Boehmite and γ-Alumina Nanorods

Boehmite nanorods were synthesized by a solvothermal method using AICl3·6H2O in mixed solvents of water and aniline. The solvothermal time, heating temperature and the concentration of aniline have effects on the morphology of boehmite. γ-alumina nanorods were prepared by a simple thermal transformation of boehmite nanorods. A rational mechanism based on the oriented attachment is proposed for the formation of boehmite nanorods. The products were characterized by X-ray powder diffraction （XRD） and transmission electron microscopy （TEM）. Photoluminescence （PL） spectrum of the boehmite nanorods was also investigated.     

Evaluation of Morphology—Stable Critical Size of KNbO3 Crystals

Skeletal form of KnbO3 crystals growing in Li2B4O7 solvent was in-situ observed at 900℃ and it was found that shallow depression started to develop on the surface of KnbO3 crystals when the crystal size exceeded several micron,typically 7 micron.Based on the quantitative criterion derived by Chernov,the estimated critical size of KNbO3 crystals was 1 micron,which was consistent with the experimental measurement.The kinetic coefficients,Kcorner and Kcr,in the criterion were experimentally obtained in the diffusive-convective and diffusive-advective flow states respectively.     

Structural Morphological and Optical Properties of SnSb2S4 Thin Films Grown by Vacuum Evaporation Method

SnSb2S4 thin films were prepared from powder by thermal evaporation under vacuum of 1.33 × 10^-4 Pa （ 10^-6 Torr） on unheated glass substrates. The effect of thickness on the structural, morphological and optical properties of SnSb2S4 thin films was investigated. Films thickness measured by interference fringes method varied from 50 to 700 nm. X-ray diffraction analysis revealed that all the SnSb2S4 films were polycrystalline in spite without heating the substrates and the crystallinity was improved with increasing film thickness. The microstructure parameters： crystallite size, strain and dislocation density were calculated. It was observed that the crystallite size increased and the crystal defects decreased with increasing film thickness. In addition, by increasing the film thickness, an enhancement in the surface roughness root-mean-square （RMS） increased from 2.0 to 6.6 nm. The fundamental optical parameters like band gap, absorption and extinction coefficient were calculated in the strong absorption region of transmittance and reflectance spectrum. The optical absorption measurements indicated that the band （Eg） gap of the thin films decreased from 2.10 to 1.65 eV with increasing film thickness. The refractive indexes were evaluated in transparent region in terms of envelope method, which was suggested by Swanepoul. It was observed that the refractive index increased with increasing film thickness.