共查询到20条相似文献,搜索用时 328 毫秒
1.
《Journal of Crystal Growth》2007,298(1):48-52
Single crystals of l-Tartaric acid (C4H6O6), an organic nonlinear optical (NLO) material, have been grown by hanging seed solution and submerged seed solution techniques at room temperature. The crystal system has been confirmed from the single crystal X-ray diffraction analysis. The crystalline perfection was evaluated using high-resolution X-ray diffractometry (HRXRD). From this analysis, it was found that the quality of the crystal is quite good. The functional groups were identified using FTIR spectroscopy. UV–vis–NIR spectrum showed the absence of absorption in the wavelength region of 220–900 nm. The second harmonic generation efficiency is 89% compared to that of standard potassium dihydrogen phosphate (KDP). The laser damage threshold value is much higher than that of KDP and closer to that of β-barium borate. 相似文献
2.
Single crystals of aluminum substituted barium hexaferrite were grown by the floating zone method with optical heating. Single crystals were produced from a melt of stoichiometric composition. The process was carried out under a pressure of 50 atm of oxygen. In the system BaO–(x)Al2O3–(6?x)Fe2O3 the region of single phase crystal growth from the melt is limited by the value x=3. For higher substitutions single-phase crystallization is not observed. The grown single crystals are cylindrical boules with a diameter of 4–5 mm and with lengths up to 50 mm. To avert cracking the crystals have been annealed during the process of growth at 1100 °C. The content of FeO in the composition of single crystals of barium hexaferrite, grown by zone melting under an oxygen pressure of 50 atm, is approximately 0.3 wt%. In the system of hexaferrite–aluminates the macroscopic magnetic moment of the material disappears at x=3. 相似文献
3.
《Journal of Crystal Growth》2006,286(2):440-444
Single crystals of bis-glycine hydrogen chloride (BGHC), a semiorganic nonlinear optical (NLO) material, have been grown by slow solvent evaporation technique. Good optical quality single crystals with dimensions up to 33×5×5 mm3 are obtained. The crystals are characterized by optical transmission spectrum, FTIR and X-ray diffraction studies. The thermal stability of the crystal is studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The second harmonic generation (SHG) efficiency of BGHC was found to be 5.6 times that of KDP. The laser damage threshold values studied in single shot mode indicates that BGHC crystal possesses a fairly high value of 9.8 GW/cm2 and thus the NLO studies confirmed the superiority of BGHC over KDP and urea crystals. The dielectric constant of the crystal was studied as a function of frequency and the results are discussed. 相似文献
4.
A new vial-in-vial vapour diffusion method for growing single crystals of fully deuterated triglycine sulphate (TGS) has been developed. Single crystals of hydrogenous TGS were also grown for comparison purposes. The crystals have been characterised using x-ray diffraction and differential scanning calorimetry. The phase transition temperature was 334.0±0.5 K for fully deuterated TGS compared to 322.3±0.3 K for hydrogenous TGS. These values compare well with the expected TC. 相似文献
5.
Lijuan Liu Haitao Zhou Xiaoling He Xin Zhang Xiaoyang Wang Fuhua Lu Changlong Zhang Weining Zhou Chuangtian Chen 《Journal of Crystal Growth》2012,348(1):60-64
Crystals of RbBe2BO3F2 up to a size of 22×18×5 mm3 have been grown by the hydrothermal method. The growth conditions were optimized mainly by adjusting the mineralizers and growth temperature. The crystals linear and nonlinear optical properties, including its transmittance spectrum and second harmonic generation from 532 to 266 nm, were measured and compared with those of flux grown crystals. A maximum conversion efficiency of 20% was obtained with a 25 ps, 10 Hz laser system. The results indicate that RbBe2BO3F2 crystals grown by the hydrothermal method show similar capability for frequency conversion compared with flux grown crystals and are promising for future deep-UV harmonic generation. 相似文献
6.
Single crystals of L‐Prolinium tartrate (C5H10NO2)+ (C4H5O6)‐, a new organic non‐linear optical material of size: 15 × 10 × 10 mm3 were grown using submerged seed solution growth method. Characterization of the crystals was made using single crystal X‐ray diffraction and density determination. Spectroscopic, thermal, optical and mechanical studies were carried out. These studies show that the crystals are thermally stable upto 161°C, transparent for the fundamental and second harmonic generation of Nd: YAG (λ = 1064 nm) laser and possess good mechanical strength. Second harmonic generation (SHG) conversion efficiency was investigated to explore the NLO characteristics of this material using Kurtz and Perry method and it was found that the SHG conversion efficiency is about 90% of that of the standard KDP crystals. Laser damage threshold study was also carried out. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
7.
Guohui Li 《Journal of Crystal Growth》2008,310(1):36-39
Regeneration process of a 330×330×20 mm3 Z-plate seed is carried out in a 1.5 metric tonnage volume crystallizer that placed in a water bath of temperature fluctuation less than ±0.02 °C within 10 days. The surface of the whole crystal was restored by the formation of a box-like structure filled with growth solution, and then the transparent layer of perfect tetragonal KDP crystal without inclusions, crack and milky regions just like those produced by traditional slow cooling technique can be grown from solution. After the regeneration, the height of KDP crystal is merely 0.5 times the side of plate seed. We found it that the optical transmission and laser damage threshold of the KDP crystals we grown are not significantly different from those of KDP crystals grown by traditional method. 相似文献
8.
Large single crystals of β-Mn2V2O7 are successfully grown at a slow cooling rate using flux method in a closed crucible. The grown crystals exhibit a characteristic morphology with natural (1 1 0) and (3 5 0) facets. X-ray diffraction and chemical analyses show that the grown crystals have high quality. 相似文献
9.
《Journal of Crystal Growth》2006,286(2):288-293
Single crystals of rare-earth orthovanadate, RVO4 where R=Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, with the cross-sectional size of about 7×7 mm2 and 20–50 mm length have been successfully grown by the floating-zone method. Fluorescence properties at room temperature and dielectric and elastic properties along the c-axis of some grown crystals have been reported. 相似文献
10.
Potassium sodium ammonium dihydrogenphosphate K0.23Na0.23(NH4)0.54H2PO4 (KSADP), a new mixed crystal has been grown in aqueous medium by the slow evaporation of equimolar mixture of ammonium dihydrogenphosphate (ADP), potassium dihydrogenphosphate (KDP) and sodium dihydrogenphosphate (SDP). Crystal composition as determined by single crystal X-ray diffraction analysis reveals that it belongs to the tetragonal system with noncentrosymmetric space group I-42d and it is structurally similar to ADP with cell parameter values, a=7.4794(4) Å; b=7.4794(4) Å; c=7.2974(11) Å; υ=408.23(7) Å3; z=4. The presence of sodium and potassium in ADP matrix was confirmed by inductively coupled plasma emission spectrometry and energy dispersive X-ray spectroscopy. The partial cationic substitution results in defect centers influencing the physical properties. Slight shifts in vibrational patterns could be attributed to strains in the lattice. Refinement of structure by single crystal XRD analysis reveals that potassium, sodium and ammonium coexist in the mixed crystal. The surface morphology of the as-grown specimen, which is changed as a result of cationic incorporation, was studied by scanning electron microscopy. The relative second harmonic generation (SHG) efficiency measurements revealed that the mixed crystal has a superior NLO activity than ADP. 相似文献
11.
Gisele Maxwell Alan Petersen Dylan Dalton Bennett Ponting 《Journal of Crystal Growth》2012,352(1):59-62
Potassium lithium niobate (KLN) is a nonlinear optical material with a high nonlinearity. It has the potential to improve the performance and reduce the cost of blue and UV lasers. KLN crystals are not commercially viable because growth by traditional techniques is not possible. In an effort to develop commercially viable KLN, single crystals of the material were grown by the laser heated pedestal growth method (LHPG) with compositions of x=0.02, 0.06 and 0.2 following K3Li2?xNb5+xO15+2x. Noncritical phase matching at 20 °C for previously unreported compositions of x=0.02 and 0.06 was measured at 795 nm and 805 nm, respectively. Overall, the results suggest that single crystal KLN can be used for SHG into the UV region of the spectrum and can be developed into a commercially viable nonlinear optical material. 相似文献
12.
Single crystals of hexakis(thiourea)nickel(II) nitrate [Ni(SC(NH2)2)6](NO3)2 are grown by slow evaporation of methanolic solution at room temperature. Structural analysis by single crystal X-ray diffraction analysis reveals that the crystal belongs to monoclinic system with space group C2/c and the cell parameters are a=22.046(2) Å, b=9.3325(4) Å, c=16.221(2) Å, Z=8. The metal is coordinated by six thiourea groups with Ni–S–C bond angles ranging from 114.81° to 116.85° and Ni–S bond lengths lying in the range 2.35 to 2.61 Å in a distorted octahedral geometry. The interesting feature observed in this study is that although it crystallizes in centrosymmetric structure, contrary to expectations, it exhibits a positive second harmonic generation (SHG) result, quite likely due to the change in stereochemical arrangement. An Nd:YAG laser with a modulated radiation of 1064 nm directed on the powdered sample leads to local noncentrosymmetry and this could be due to the loss of thiourea ligands resulting in tetrakis(thiourea)nickel(II) complex causing green light emission. The powder X-ray diffraction study reveals the crystallinity of the grown material. The vibrational patterns in FT-IR clearly evidence the complex formation. Thermogravimetric analysis (TG) reveals the purity of the sample and no decomposition is observed up to the melting point. The crystal is further characterized by diffused reflectance spectroscopy, dielectric studies and microhardness analysis. 相似文献
13.
We studied the effect of Dy3+ content on the magnetic properties of cobalt ferrite single crystal. The single crystals of CoFe1.9Dy0.1O4 were grown by the flux method using Na2B4O7.10 H2O (Borax) as a solvent (flux). The black and shiny single crystals were obtained as a product. The X-ray diffraction analysis at room temperature confirmed the spinel cubic structure with lattice constant a=8.42 Å of the single crystals. The compositional analysis endorses the presence of constituents Co, Fe and Dy elements after sintering at 1300 °C within the final structure. The magnetic hysteresis measurements at various temperatures viz. 10 K, 100 K, 200 K and 300 K reveal the soft ferrimagnetic nature of the single crystal than that of for pure CoFe2O4. The observed saturation magnetization (Ms) and coercivity (Hc) are found to be lower than that of pure CoFe2O4 single crystal. The magnetostriction (λ) measurement was carried out along the [001] direction. The magnetic measurements lead to conclude that the present single crystals can be used for magneto-optic recording media. 相似文献
14.
《Journal of Crystal Growth》1999,196(1):122-125
Single crystals of CaGdAlO4 that have not been used previously as a substrate material for HTSC films were grown by Czochralski method and applied for the deposition of the Bi2Sr2CaCu2O8−x and LuBa2Cu3O7−z thin films. The main advantages of the CaGdAlO4 crystals are sufficiently low dielectric constant, appropriate crystal lattice match with most HTSC, fairly high crystal perfection and reproducibility of the growth process. Bi2Sr2CaCu2O8−x films were prepared by “off-axis” DC magnetron sputtering and LuBa2Cu3O7−z films were obtained by flash evaporation MOCVD technique on the (0 0 1) oriented CaGdAlO4 substrates. 相似文献
15.
《Journal of Crystal Growth》2003,247(1-2):131-136
Single crystals in the xBiScO3–yBiGaO3–(1−x−y)PbTiO3 (BS–BG–PT) system were grown by the high temperature solution method using Pb3O4 and Bi2O3 as the flux. The dielectric permittivity (εr) at room temperature for unpoled tetragonal crystals was determined to be 500–600 with dielectric loss tangents less than 0.3%. The Curie temperature was found to be around ∼420–450°C, with a dielectric maximum, exhibiting relaxor behavior. The longitudinal piezoelectric coefficient (d33) was found to be ∼300 pC/N for 〈0 0 1〉 oriented tetragonal crystals with electromechanical coupling factor (k33) of 75%, with a shear mode, d15∼290 pC/N and k15∼45%, lateral mode, d31∼−55 pC/N and k31∼−37%. The remnant polarization (Pr) was 46 μC/cm2 with a coercive field (Ec) of 43 kV/cm at 1 Hz and DC field of 60 kV/cm. The linear electro-optic (E-O) coefficients of poled crystals determined using an automated scanning Mach–Zehnder interferometer method at room temperature and wavelength of 632.8 nm were r33=36 and r13=4 pm/V, respectively. 相似文献
16.
《Journal of Crystal Growth》2007,298(1):30-36
Single crystals of bis-glycine sodium nitrate (BGSN), a semi-organic nonlinear optical (NLO) material, have been grown by slow cooling method. Good optical quality single crystals with dimensions up to 1.6×1.6×1.0 cm3 are obtained. Using a single-crystal diffractometer, the morphology of BGSN crystal was identified. Powder X-ray diffraction confirms the crystalline nature of BGSN. The grown crystals were characterized by optical transmission spectrum (UV) and FTIR studies. The NLO property of the crystal was confirmed by Kurtz second harmonic generation (SHG) test, and the output power generated by the crystal was compared with that of KDP. The thermal stability of the crystal was studied by thermo-gravimetric analysis (TGA), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). Micro hardness study was carried out for different planes, and the anisotropy behavior of the crystal was observed. 相似文献
17.
G. Ramasamy G. Bhagavannarayana G. Madhurambal Subbiah Meenakshisundaram 《Journal of Crystal Growth》2012,352(1):137-142
Mixed crystals ZnxMg(1?x)(NH4)2(SO4)2·6H2O of the two well-known Tutton's salts Zn(NH4)2(SO4)2·6H2O and Mg(NH4)2(SO4)2·6H2O were grown with varying molar proportions (x=0.10–0.90) by slow evaporation solution growth technique. The mixed crystal Zn0.54Mg0.46(NH4)2(SO4)2·6H2O is crystallizing in monoclinic system with space group P21/c and cell parameters a=6.2217(4) Å, b=12.5343(7) Å, c=9.2557(6) Å, β=106.912(3)°. The coexistence of zinc and magnesium ions in the mixed crystal was confirmed by inductively coupled plasma (ICP), atomic absorption spectroscopy (AAS) and energy dispersive X-ray spectroscopy (EDS). Compositional dependence of lattice parameters follows Vegard's relations. Slight variations are observed in FT-IR and XRD of pure and mixed crystals. Comparison of crystalline perfection as evaluated by high-resolution X-ray diffraction (HRXRD) for mixed crystals of various proportions reveals a reasonably good crystalline perfection for the mixed crystal with nearly equimolar ratio of Zn and Mg. The surface morphology of the mixed crystals changing with composition was studied by scanning electron microscopy (SEM). UV–vis studies reveal that the transparency of the mixed crystals was not much affected. 相似文献
18.
Microcrystalline silicon–germanium alloys for solar cell application: Growth and material properties
《Journal of Non》2006,352(9-20):1255-1258
Microcrystalline silicon–germanium (μc-Si1−xGex:H) alloy films have been grown by 100-MHz glow-discharge of a SiH4/GeH4/H2 gas mixture. Alloys over a full range of compositions were prepared to gain a comprehensive understanding of their growth and material properties. With increasing GeH4 concentration in the gas-phase, we observed a preferential Ge incorporation behavior in the solid. Growth rate studies revealed that the Ge incorporation efficiency from source gas to solid is about five times greater than for Si at growth temperature of 200 °C, which accounts for the variation of alloy composition. With increasing Ge incorporation in the solid, on the other hand, we find a monotonic decrease in photoconductivity, followed by an electrical transition from weak n-type to strong p-type conduction at x > 0.7. At x ≈ 0.4, however, we obtained relatively high photoconductivity gains by a factor of 20 and strong infrared response in the solar cell structure. The Ge incorporation behavior and its effect on charge carrier transport are discussed. 相似文献
19.
Lingyun Li Guojian Wang Yisheng Huang Lizhen Zhang Zhoubin Lin Guofu Wang 《Journal of Crystal Growth》2011,314(1):331-335
An Nd3+:Ca9Gd(VO4)7 crystal with dimensions of ?25×30 mm3 was grown by the Czochralski method. The hardness, thermal expansion coefficient and thermal conductivity coefficient of the crystal were measured. The spectroscopic characteristics of Nd3+:Ca9Gd(VO4)7 crystals were investigated. The absorption band at 810 nm has an FWHM of 10 nm, and absorption cross-sections are 5.81×10?20 cm2 for π-polarization and 7.47×10?20 cm2 for σ-polarization at 810 nm. The emission cross-sections at 1067 nm are 4.2×10?20 and 6.5×10?20 cm2 for π- and σ-polarizations, respectively. The quantum efficiency ηc is equal to 94.3%. To sum up the above results, Nd3+:Ca9Gd(VO4)7 crystal can be regarded as a highly efficient solid state laser material. 相似文献
20.
Single crystals of La2NaTaO6 were grown out of a reactive high-temperature hydroxide melt. The structure was determined by single crystal X-ray diffraction. La2NaTaO6 adopts the monoclinically distorted double perovskite structure type with general formula A2BB′O6, where tantalum atoms are located on the B′ site. La2NaTaO6 crystallizes in the monoclinic space group P21/n with a=5.6904(2) Å, b=5.9824(2) Å, c=8.1423(2) Å and β=90.8650(10)°? An optical bandgap of 4.5 eV was estimated from the UV–vis diffuse reflectance spectrum. 相似文献