共查询到20条相似文献，搜索用时 15 毫秒
1.
T. O. dos Santos J. F. Carvalho A. C. Hernandes 《Crystal Research and Technology》2004,39(10):868-872
The synthesis of Bi2O3‐Nb2O5 sillenite phase (BNbO) and the solubility of this phase with Bi12TiO20 was investigated by solid‐state reaction synthesis and niobium doped Bi12TiO20 (BTO:Nb) crystals were grown by the Top Seeded Solution Growth (TSSG) technique. The structures of polycrystalline compounds were checked by X‐ray powder diffraction method at room temperature. The correct composition of the sillenite phase stabilized with niobium was determined as Bi12[Nb0.17Bi0.83]O19.7 (BNbO) with unit cell parameter a = 10.261(2) Å. The system BTO‐BNbO is poorly soluble, but niobium doped BTO crystals were grown from the liquid composition 10Bi2O3 : xTiO2 : (1‐x)/2 Nb2O5, with x = 0.95 and 0.90. A niobium concentration limit in the liquid phase is established in order to grow BTO:Nb with good crystalline quality. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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A protocol for growing sets of nearly uniform size crystals was devised and tested experimentally. The experiments were centered on insulin because of its medical significance however the method is applicable to other substances as well (C.N. Nanev, V.D. Tonchev, F.V. Hodzhaoglu, Protocol for growing insulin crystals of uniform size, J. Cryst. Growth 375 (2013)10–15). Now, both growth and dissolution of equally‐sized crystals are described quantitatively by a common analytical model. In our model the emphasis is put on the dissolution case when crystals number and/or size are sufficiently large to secure reaching solubility, while some non‐dissolved crystalline substance is still remaining. Quantitative results are obtained for the relations between dimensionless values of crystal size, solution concentration and time elapsed, the assumption simplifying our calculations being that the crystals retain their shape during the entire dissolution process. 相似文献
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我们生长了掺镁量分别为3.0mol;、5.0mol;、7.8mol;、9.0mol;的76mm高掺镁铌酸锂晶体,检测了这些晶体的生长条纹情况,并利用双光耦合配置测试了这些晶体在351nm紫外光下的光折变性能.从实验结果看,采用同成分共熔点铌锂配比的高掺镁铌酸锂晶体生长条纹比较多;虽然高掺镁铌酸锂晶体在可见光波段有很好的抗光折变能力,但是在紫外光下具有良好的光折变性能,可以作为优良的紫外光折变材料使用.同时,实验结果表明,掺镁量在5.0mol;的铌酸锂晶体具有最佳的紫外光折变性能. 相似文献
4.
B. Suresh Kumar M. R. Sudarsana Kumar K. Rajendra Babu 《Crystal Research and Technology》2008,43(7):745-750
Single crystals of pure and lithium substituted L‐alanine are successfully grown by slow evaporation method at constant temperature of 32°C. The effect of lithium dopant on crystal properties has been studied. Powder and single crystal XRD analysis confirms the structure and change in lattice parameter values for the doped crystals. The crystals were characterized by solubility studies, density, melting point measurements, FTIR and UV‐Vis‐NIR techniques. Thermal and mechanical stability of crystals were tested by TGA/DTA and micro hardness analysis. NLO activity of the crystals is found to be increased in the presence of lithium ions. The dielectric constant and dielectric loss of the crystals were studied as a function of frequency. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
5.
《Journal of Applied Crystallography》2018,51(4):1257-1258
A design for an air‐cooled tube (`crystallization incubator') installed in a laboratory tube furnace is presented. The setup allows regulation and simultaneous crystallization of several substances at different temperature gradients and rate intervals, with the purpose of obtaining crystals. 相似文献
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A design for an air‐cooled test tube with a series of sockets and plugs (`crystallization socket‐outlet adaptor') installed in a laboratory furnace is presented. The setup allows easy regulation and simultaneous crystallization tests of a series of different crystallization parameters and substances, enabling fast studies of single‐crystal growth. 相似文献
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The conductivity, mobility, photoconductivity and photo response measurements in GaS0.75Se0.25 mixed crystals were carried out in the temperature range of 150‐450 K. The room temperature conductivity, mobility and electron concentration values were 10‐9 (Ω‐cm)‐1, 48 cm2V‐1s‐1 and ∼109 cm‐3, respectively. Two donor levels were obtained from temperature‐dependent conductivity and carrier concentration, located at energies of about 755 and 465 meV below the conduction band. Single donor‐single acceptor analysis yields the same donor level at 465 meV with donor and acceptor concentrations of 8.7 × 1014 and 5.3 × 1013 cm‐3, respectively. The mobility‐temperature dependence shows that ionized impurity scattering dominates the conduction up to the temperature 310 K with different temperature exponent, while above this critical temperature; the phonon scattering is dominant conduction mechanism. From the photo‐response spectra, the maximum photocurrent was observed for all the samples at 2.42 eV, and varied slightly with temperature. Moreover, the photocurrent‐light intensity dependence in these crystals obeys the power law, Iph ∝ ϕγ with γ between 1.7 and 2.0 for various applied fields and temperatures. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
10.
Nikolay V. Abrosimov Vladimir N. Kurlov Robert Schewski Jan Winkler 《Crystal Research and Technology》2020,55(2):1900097
This contribution presents the growth of Si1−xGex crystals with constant gradient of composition for X-ray or γ-ray diffraction optics using automated control of the crystal shape during the growth process. The key idea is to achieve a constant concentration gradient by continuously decreasing the crystal diameter during the main crystal growth phase. For this purpose a concept has been developed for a proper planning of the radius trajectory matching all technological requirements. Si1−xGex single crystals with constant gradients between 0.10 and 0.16 at% cm−1 have been grown using an automated control system. 相似文献
11.
Forsterite monocrystals doped with Ti and Ni were grown by the flux growth technique. A suitable mixture of flux (MoO3, V2O5, Li2CO3) and nutrient was slowly cooled down to 750 °C from 1250 °C or 1350 °C. The crystals were then characterized by powder and single‐crystal X‐ray diffraction, scanning electron microscopy and differential scanning calorimetry (DSC). Variations observed in crystal size were attributed by both the varying experimental conditions in which they had been obtained, and to the amount of Ni substituted for Mg in the structure. High abundances of doped forsterite required a cooling rate of 1.8 K h‐1. These synthetic, well‐characterized Ti and Ni doped forsterite crystals may have potential for exploitation in industrial fields. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Single crystals of L‐tartaric acid (LTA), an organic nonlinear optical material, have been grown using a home‐built crystal growth setup (the Moovendaran–Kalyanasundar–Natarajan setup). Crystals of LTA were also grown by the slow evaporation solution technique. These single crystals were characterized using single‐crystal X‐ray diffraction, high‐resolution X‐ray diffraction, and IR and UV–Vis–NIR spectroscopy. In addition, measurements of Vickers microhardness, laser damage threshold value and second harmonic generation efficiency are reported. Thermal, dielectric and photoluminescence studies were also carried out. 相似文献
14.
O. M. Bunoiu I. Nicoara J. L. Santailler F. Theodore T. Duffar 《Crystal Research and Technology》2005,40(9):852-859
Ribbon and rod sapphire pulling has been performed in three different crystal growth equipments in order to study the effect of the installation, of the atmosphere, of the die shape, of the feed material and of the pulling rate on the distribution, number and diameter of the characteristic voids (micro‐bubbles) in the crystals. The location of the bubbles in the crystals depends on the die geometry; however, in most cases they are essentially located close to the crystal periphery and then can be efficiently removed by lapping. After statistical analysis of the results, it is demonstrated that the number of gas moles incorporated in the crystals, inside the voids, is totally independent of any growth parameter. It is also shown that the bubble diameter depends only on the pulling rate. Consequently, for a given pulling rate, the number of bubbles auto‐adjusts in order to satisfy the constant molar gas incorporation. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
15.
O. Karabulut M. Parlak R. Turan U. Serincan B. G. Ak&#x;nolu 《Crystal Research and Technology》2006,41(3):243-249
The structure and temperature dependent spectral photoconductivity of as‐grown and N‐and Si‐implanted GaSe single crystals have been studied. It was observed that post‐annealing results in a complete recovery of the crystalline nature that was moderately reduced upon implantation. The band edge is shifted in the implanted sample which is attributed to the structural modifications and continuous shallow levels introduced upon implantation and annealing. Our calculations showed that the trap density is increased upon implantation and annealing which confirms a possibility of explanation the phenomenon within a framework of continuous trap levels. Photocurrent measurements as a function of photo‐excitation intensity also support continuous distribution of localized states in the band gap. © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim 相似文献
16.
Crystal morphology control is a common concern for the crystal engineering and relevant applications. For example, urate crystallization is important for the study of the hyperuricemia induced gout. Herein, biomimetic hydrogel material with uniform surface and vertical structure is fabricated, which possesses hybrid pH-temperature responsibility for high-efficiency interfacial nucleation and concentration regulation functions. The developed hydrogel layers are prepared to slice type as a functional microplatform and then added into the uric acid dihydrate (UAD) crystal solution to induce monosodium urate monohydrate (MSUM) crystallization. With different dosage of the hydrogel slices (HGS) in the solution, diverse crystal morphologies can be obtained in an efficient manner, such as “flower,” “sphere,” “sticky spheres,” which entirely distinguishes from the one prepared via no-HGS. This work explores a new path for revealing the relevant crystallization mechanism and developing crystal morphology control technology with hydrogel interfacial materials. 相似文献
17.
Takahiro Yamada Hisanori Yamane Takaaki Ohta Takenari Goto Takafumi Yao 《Crystal Research and Technology》2007,42(1):13-17
GaN crystals were prepared by heating a Ga melt with 1 at% Li3N against Ga at 750 °C in Na vapor under N2 pressures of 0.4–1.0 MPa. The GaN crystals grown at 1.0 MPa of N2 were colorless and transparent prismatic, having a size of approximately 0.7 mm in length. A secondary ion mass spectrometry (SIMS) showed the contaminant of lithium in the obtained crystals. A large broad yellow band emission peak of 2.28 eV was observed at room temperature in the photoluminescence spectrum in addition to the near band emission peak of GaN at 3.39 eV and a small broad satellite emission at 3.24 eV. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
18.
钒酸盐系列激光晶体制备和性能研究 总被引：2，自引：0，他引：2
用提拉法生长了Nd∶YVO4, Nd∶GdVO4,Nd∶GdxLa1-xVO4(x=0.8, 0.6, 0.45)系列晶体,对影响晶体质量的因素进行了分析,测量了几种晶体的结构和晶胞常数;测量了Nd∶YVO4, Nd∶GdVO4, Nd∶Gd0.8La0.2VO4和Nd∶Gd0.6La0.4VO4晶体的室温吸收谱和荧光谱,用LD泵浦Nd∶YVO4, Nd∶GdVO4, Nd∶Gd0.8La0.2VO4晶体,实现了1.06μm和1.34μm的激光输出. 相似文献
19.
A. Majchrowski M. T. Borowiec J. Zmija H. Szymczak E. Michalski M. Bara&#x;ski 《Crystal Research and Technology》2002,37(8):797-802
Top Seeded Solution Growth (TSSG) technique has been used to produce Bi12TiO20 (BTO) and some mixed Bi12Ti0.8M0.2O20 single crystals in which Ti was substituted with M=V, Pb or Ga. Pure Bi40Ga2O63 (BGaO) single crystals have been grown, too. Thermal conditions enabling growth of uniform [110] sillenite single crystals with totally flat (110) interface have been found. Influence of composition on spectral characteristics of the BTO mixed crystals has been investigated. 相似文献