Crystal Growth Characteristics Research Articles

Solubility Metastable Zone Width Measurement and Crystal Growth of the 1:1 Benzoic Acid/Isonicotinamide Cocrystal in Solutions of Variable Stoichiometry

The solubility and crystal growth of the 1:1 cocrystal between benzoic acid and isonicotinamide from 95% ethanol was studied through the creation of a ternary phase diagram at differing temperatures and turbidity measurements. From the solubility measurements thermodynamic properties of the system were evaluated, which indicate little solution binding of the two components supported by in situ FT-IR spectra. Cooling crystallisation from solutions of differing composition suggests differing crystal growth characteristics. An excess of benzoic acid appears to increase the metastable zone width and reduce the crystal size through interactions along the fastest growth axis, while an excess of isonicotinamide decreases the metastable zone width with increased crystal size.

The Growth and Characterization of the Cerium Contained Inorganic Halide Scintillators

A report on the crystal growth, luminescence and scintillation characteristics of two developed scintillators, CsCe2Cl7 and Cs2NaCeCl6 are presented. CsCe2Cl7 is a new scintillation material. These crystals were grown by the Czochralski pulling technique. The X-ray diffraction technique was used to verify the structure of crystals. Under the X-ray excitation emission, the CsCe2Cl7 showed a broad emission band in the wavelength range from 370 to 470 nm while the Cs2NaCeCl6 crystal showed a spectrum in the wavelength range from 370 to 440 nm. The energy resolutions (FWHM of peak position) for the 662 keV full energy peak of 5.5% and 8.3% were observed at room temperature for the CsCe2Cl7 and Cs2NaCeCl6 crystals, respectively. The scintillation decay time measurement curves showed that, CsCe2Cl7 crystal has a single exponential decay function with a decay time of 50 ns. The Cs2NaCeCl6 crystal exhibited three main decay time components, a short component with a decay time constant of 91 ns and 36% intensity, an intermediate component with a decay time constant of 601 ns and intensity 33%, followed by a long component with a 3.2 µs decay time constant and an intensity of 31% of the total light yield. On the basis of the scintillation results of these materials grown, it is believe that these scintillation crystals can find a place in medical imaging and radiation detection system.

Crystal growth and scintillation characteristics of the Nd 3+ doped LaF 3 single crystal

Two-inch diameter Nd 3+ doped LaF 3 single crystals were successfully grown by the Czochralski technique. No remarkable absorption due to unfavorable impurities or color centers was observed from optical absorption measurements in the vacuum ultra-violet spectral region. The high crystallinity and homogeneous Nd 3+ distribution were found from X-ray rocking curve and chemical composition analysis, respectively. X-ray excited luminescence spectrum was measured and the significant 4f 25d–4f 3 luminescence at 173 nm was observed in the grown crystal. The pulse height spectrum and scintillation decay curves were taken upon γ-ray irradiation. As a result, the grown crystals demonstrated sufficient response to the γ-ray, the light yield of 140 ± 30 photons/MeV, and fast scintillation decay of 7.6 ns.

Efficient nonlinear optical material BiB3O6 (BIBO)

This review is devoted to a new nonlinear optical material BiB3O6 (BIBO). It systemizes data on the phase equilibrium, structure, polymorphism, and growth characteristics of single crystals of this compound and considers its main properties and fields of application. The bibliography includes 122 references.

Al-induced low-temperature crystallization of Si 1 − xGe x (0 < x < 1) by controlling layer exchange process

Low-temperature (< 450 °C) Al-induced crystallization (AIC) of a-Si 1 − x Ge x (0 < x < 1) films on an insulator has been investigated using a-Si 1 − x Ge x /Al/quartz stacked structures. It was found that the crystal growth features drastically depends on the Ge fraction. Change of the stacked structures to Al/poly-SiGe/quartz uniformly occurred by annealing for low Ge fractions (< 50%). However, the layer exchange and crystallization occurred locally and heterogeneously for high Ge fractions (> 50%). To realize uniform crystallization for high Ge fractions, effects of interfacial Al oxide layer thickness on layer exchange were investigated. By optimizing the oxide layer thickness, the layer exchange process could be controlled, and thus, homogeneous crystallization with large grain sizes (> 20 μm) was achieved for samples with the whole Ge fractions. These findings will be a powerful tool for realizing large poly-SiGe on insulating films for high-efficiency thin-film solar cells and system-in-displays.

Crystal Growth in the Foliated Aragonite of Monoplacophorans (Mollusca)

Crystal-growth features of the foliated aragonite from two species of the rare monoplacophoran molluscs have been analyzed. The crystals have unique morphologies. They are very thin along the c axis and elongated along the a axis, and their arrangement varies depending on the species. Surface energy minimization in the crystal arrangement observed in Micropilina leads to a discrete number of constant angular relationships, which is explained by twin laws and epitaxy. Textural analysis shows that crystals form oriented aggregates with their c axes perpendicular to the shell surface. Close to the shell margin, crystals compete so as to orient their a axes nearly perpendicular to the growth front of the lamellae, although the scattering of the a axis soon increases toward the shell interior. In contrast to inorganic crystals, growth along the c axis is inhibited by organic molecules. Their incorporation may be related to the existence of weak intermolecular interactions between CO3 groups along this axis. Co...

Insight into growth details and characteristics of windmill-like polyethylene crystals

The crystallization detail of polyethylene (PE) has been scarcely studied via in-situ approach since it is an extremely fast process. In this work, optical microscopy is used to investigate crystallization details and characteristics of windmill-like polyethylene crystals. It has been shown that the straight edges of the petals appear firstly and grow in pairs from their central junctions, which subsequently induce the surrounding domains in between each pairs of petals to nucleate and crystallize into twisted lamellar overgrowths. The remaining terrace-stacked lamellae which form curved edges of the petals start to develop only after the straight edges of the petals together with the twisted lamellar overgrowths have completed their growth. It is confirmed that the preferential growth direction of these petals are along crystallographic [113] axis, which has an angle of 65, with the typical direction along b-axis adopted also by the twisted lamellar overgrowths.

Growth, thermal and spectroscopic characteristics of LiNd(WO 4) 2 crystal

Crystal growth, thermal and optical characteristics of LiNd(WO 4) 2 crystal have been investigated. The LiNd(WO 4) 2 crystal up to Ø15 × 32 mm 3 has been grown by Czochralski technique. The hardness is about 5.0 Mohs’ scale. The specific heat at 50 °C is 0.42 J g −1 K −1. The thermal expansion coefficient for c- and a- axes is 1.107 × 10 −5 and 2.104 × 10 −5 K −1, respectively. The absorption and fluorescence spectra and the fluorescence decay curve of LiNd(WO 4) 2 crystal were measured at room temperature. Some spectroscopic parameters such as the intensity parameters, the spontaneous transition probabilities, the fluorescence branching ratios, the radiative lifetimes and emission cross sections were estimated.

Crystal-Growth Behavior in Ca−Mg Carbonate Bacterial Spherulites

Spherulites composed of aragonite, magnesian calcite, and calcian-magnesian (-manganoan) kutnahorite-type carbonates were precipitated by two halophilic bacterial strains in porous solid as well as liquid media at high salinity. Although Mg and Ca are geochemically similar elements, Ca is preferentially incorporated into aragonite structures in liquid media whereas Mg remains in the solution and/or precipitates to form struvite crystals. In solid media, crystal growth features clearly correlate with reticular parameters and the Mg content of the Ca−Mg and Ca−Mg(Mn) carbonates. The increased salinity in these media leads to the incorporation of Mg (and Mn) into the carbonate structure under growth conditions farther and farther from equilibrium. Although calcite is the stable phase in the Earth surface environments, carbonates denser than pure calcite, like aragonite and Mg-rich calcite, are kinetically favored in the studied bacterial precipitates.

Light‐Emitting Rubrene Nanowire Arrays: A Comparison with Rubrene Single Crystals

AbstractThis is a report on a new method of growth of a light‐emitting rubrene nanowires array with diameters of 200 ± 10 nm by using organic vapor transport through Al2O3 nanoporous templates. Nanometer‐scale laser confocal microscope (LCM) photoluminescence (PL) spectra and crystalline structures of the rubrene nanowires are compared with those of rubrene single crystals prepared with the same experimental conditions without the template. In the LCM PL spectra it is observed that the PL spectra and intensity varies with the detecting positions because of the crystal growth characteristics of the rubrene molecules. A single rubrene nanowire has a wider LCM PL band width than that of the rubrene single crystal. This may originate from the light emissions of the mixed polarized bands due to additional new crystallinity in the formation of the nanowires. From the current–voltage characteristic curves, the semiconducting nature of both the rubrene nanowires and single crystals is observed.

Organic Phenolic Configurationally Locked Polyene Single Crystals for Electro‐optic and Terahertz Wave Applications

AbstractWe investigate a configurationally locked polyene (CLP) crystal 2‐(3‐(4‐hydroxystyryl)‐5,5‐dimethylcyclohex‐2‐enylidene)malononitrile (OH1) containing a phenolic electron donor, which also acts as a hydrogen bond donor. The OH1 crystals with orthorhombic space group Pna21 (point group mm2) exhibit large second‐order nonlinear optical figures of merit, high thermal stability and very favorable crystal growth characteristics. Higher solubility in methanol and a larger temperature difference between the melting temperature and the decomposition temperature of OH1 compared to analogous CLP crystals, are of advantage for solution and melt crystal growth, respectively. Acentric bulk OH1 crystals of large sizes with side lengths of up to 1 cm with excellent optical quality have been successfully grown from methanol solution. The microscopic and macroscopic nonlinearities of the OH1 crystals are investigated theoretically and experimentally. The OH1 crystals exhibit a large macroscopic nonlinearity with four times larger powder second harmonic generation efficiency than that of analogous CLP crystals containing dimethylamino electron donor. A very high potential of OH1 crystals for broadband THz wave emitters in the full frequency range of 0.1–3 THz by optical rectification of 160 fs pulses has been demonstrated.

Growth and optical characteristics of Er 3+:LiLa(MoO 4) 2 crystal

Crystal growth and optical characteristics of Er 3+:LiLa(MoO 4) 2 crystals were investigated. The Er 3+:LiLa(MoO 4) 2 crystal up to Ø 21 × 33 mm 3 was grown by Czochralski method. The hardness of Er 3+:LiLa(MoO 4) 2 crystal is 371.2 VDH. The specific heat at 50 °C is 0.41 J g −1 K −1. The absorption spectra, fluorescence spectra and the fluorescence decay curve of Er 3+:LiLa(MoO 4) 2 crystal were measured at room temperature. Some spectroscopic parameters such as the intensity parameters, the spontaneous transition probabilities, the fluorescence branching ratios, the radiative lifetimes and the emission cross-sections were estimated.

The Formation and Growth Behavior of Aluminium Boride Crystals in an Al–B Alloy

The formation of borides in an Al–3 wt.% B alloy produced from reaction between aluminium and boron oxide (B2O3) has been investigated. Melting and cooling experiments were carried out to explore the growth characteristics of aluminium boride crystals. During heating up to1300 oC boron dissolved into molten aluminium and subsequently cooled to form solid aluminium borides in the aluminium matrix. At room temperature boride particles was identified as AlB2. Although, AlB12 phase is the first phase to form directly from the Al-B liquid above 1000 oC which transforms to stable AlB2 crystals by a peritectic reaction during cooling. Scanning electron microscope (SEM) and X-ray diffraction (XRD) techniques were employed. Results showed that the shape and distribution of the borides are dependent on the cooling conditions of the liquid Al-B alloy.

Gasdynamic effects during the growth of crystalline gallium nitride via chloride-hydride epitaxy in a vertical reactor

The growth of crystalline gallium nitride during chloride-hydride vapor epitaxy in a vertical reactor is numerically simulated. The effects of a break in the stability of the gas flow and the related changes in the crystal growth characteristics are analyzed; these changes are caused by changes in the flow rates of the gas components and in the crystal position with respect to the source of gallium. Free concentrational convection is found to substantially affect the crystal growth rate distribution over the crystal surface.

Preferred Orientation of Inconel 690 after Vibration Arc Oscillation Welding

To evaluate the crystal growth characteristics of vibration welding, Inconel 690 alloy was welded when subjected to synchronous mechanical vibrations. This study employs arc oscillation welding along with vibrations to obtain structures with the preferred orientation. The results show that the surface normal orientation of grains in vibrationless weld was {420} preferentially, but they were {200}, {311} and {420} preferentially in vibration welding. The microstructure between the first and the second pass weldings illustrates that vibrations disconnect the dendrite growth from the first pass weld to the second. The most recent grains were formed without relating to the neighbouring grain. In the vibrationless weld, the grain orientation was either parallel or perpendicular to the orientation of the nearby grains. Hence, the grains subjected to vibration welding have three orientations, but only one when subjected to vibrationless welding. On the other hand, secondary dendrite arms were rarely observed during vibration welding, but dendrites with orientations parallel to the vibration could grow easily and strongly. This result illustrates that vertical vibration encourages vertical dendrite growth and restricts their horizontal growth. [doi:10.2320/matertrans.MEP2007305]

Effects of residence time and mixing regimes on the precipitation characteristics of CaF 2 and MgF 2 from high ionic strength sulphate solutions

The presence of calcium (Ca) and magnesium (Mg) in the hydrometallurgical processing of base metals is responsible for the contamination of the final product, high energy consumption and large bleed streams during electrowinning. This paper elaborates on the use of ammonium fluoride to precipitate Ca and Mg as their respective fluoride minerals, namely, fluorite and sellaite. The effects of residence time and mixing regimes on crystal growth characteristics and the derived particle size distributions were investigated. The mixing levels in a typical mixed-suspension–mixed-product-removal (MSMPR) were represented by 3 possible mixing regimes; micro-, meso- and macromixing. A three-zone experimental setup was used to study the effects of the micro-, meso-, and macromixing on the crystal size distribution and filterability of fluorite and sellaite. The ionic strength of the sulphate solutions used was similar to those found in base metal leach circuits. As a result, SEM-images of the formed crystals depicted stable agglomerates of around 20 μm consisting of smaller particles in the range of 1–3 μm. The filter cake resistance was found to be around 4.0 × 10 9 m 3/kg m 2, and did not vary significantly for the experimental conditions chosen for the 3-zone experiment. The residence time did have a small but significant effect on increasing the mean and median of the particles size distributions. Increase in both macromixing and micromixing resulted in a decrease of the mean particle size, while no significant difference was noticed for mesomixing of the reactant streams.

Engineered periodic-poled lithium niobate structures doped with rare earths for multi-self-frequency conversion

LiNbO3-engineered structures, where different multi-self-frequency conversion processes are possible, are of key importance for its potential use in integrated and computational optics. Rare earth laser ions Nd3+ and Yb3+ with different concentrations have been used, and codoped with Mg oxide to eliminate the undesired photorefractive effect. The crystal growth characteristics, structural and compositional properties of the different engineered domain structures will be discussed. The nonlinear optical properties and applications of prepared structures are also shown.

Crystal growth and spectral analysis of Dy3+ and Er3+ doped KPb2Cl5 as a mid‐infrared laser crystal

AbstractThis paper reports crystal growth and optical characteristics of dysprosium (Dy3+) and erbium (Er3+) doped mid‐infrared laser crystal ternary‐potassium‐lead‐chloride (KPb2Cl5). Two transparent crystals with good optical quality have been grown successfully by using the Bridgman technique,the largest crystal size reaches up to ∅︁10×60mm2. Measurements of X‐ray diffraction(XRD) and absorption spectra were carried out. Based on Judd‐Ofelt theory, the intensity parameters Ωt(t=2,4,6), the experimental and theoretical oscillator strengths have been obtained.The intensity parameters Ωt(t=2,4,6) of Er3+:KPb2Cl5 were calculated to be Ω2=5.10×10‐20 cm2, Ω4=1.25×10‐20 cm2, Ω6=0.83×10‐20 cm2, and the values for Dy3+:KPb2Cl5 were calculated to be Ω2=6.26×10‐20 cm2, Ω4=2.45×10‐20 cm2, Ω6=0.04×10‐20 cm2 respectively. (© 2007 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Microstructures and Dielectric Characteristics of Ultrafine-Grained Barium Titanate-Based Ceramics for Base-Metal-Electrode Multilayer Ceramic Capacitors Applications

Ultrafine-grained ceramics based on barium titanate for base-metal-electrode multilayer ceramic capacitors (BME-MLCCs) applications have been prepared. X-ray diffraction analysis was used to identify the phase compositions of the ceramics. The microstructures were characterized by scanning electron microscopy and transmission electron microscopy. The effects of different dopant contents on the crystal structures, grain growth, microstructures, and dielectric characteristics of the ceramics were investigated. Desired core–shell structures have been observed and the relationships of composition, crystal structure, grain growth, and microstructure have been discussed. The present ceramics show an average grain size of 180 nm and homogeneous microstructures, as well as a high dielectric constant, a low degree of dielectric loss and good X7R temperature characteristics, which would be promising candidates for next-generation BME-MLCC applications.

Some features of single crystal growth from a crucible with skull

Some features of single crystal growth from a crucible with skull