Crystals

10 pages, 3114 KiB

Open AccessArticle

Adenine as a Halogen Bond Acceptor: A Combined Experimental and DFT Study

by Yannick Roselló, Mónica Benito, Elies Molins, Miquel Barceló-Oliver and Antonio Frontera

Crystals 2019, 9(4), 224; https://doi.org/10.3390/cryst9040224 - 25 Apr 2019

Cited by 18 | Viewed by 4072

In this work, we report the cocrystallization of N⁹-ethyladenine with 1,2,4,5-tetrafluoro-3,6-diiodobenzene (TFDIB), a classical XB donor. As far as our knowledge extends, this is the first cocrystal reported to date where an adenine derivative acts as a halogen bond acceptor. In [...] Read more.

In this work, we report the cocrystallization of N⁹-ethyladenine with 1,2,4,5-tetrafluoro-3,6-diiodobenzene (TFDIB), a classical XB donor. As far as our knowledge extends, this is the first cocrystal reported to date where an adenine derivative acts as a halogen bond acceptor. In the solid state, each adenine ring forms two centrosymmetric H-bonded dimers: one using N1···HA6–N6 and the other N7···HB6–N6. Therefore, only N3 is available as a halogen bond acceptor that, indeed, establishes an N···I halogen bonding interaction with TFDIB. The H-bonded dimers and halogen bonds have been investigated via DFT (Density Functional Theory) calculations and the Bader’s Quantum Theory of Atoms In Molecules (QTAIM) method at the B3LYP/6-311+G* level of theory. The influence of H-bonding interactions on the lone pair donor ability of N3 has also been analyzed using the molecular electrostatic potential (MEP) surface calculations. Full article

(This article belongs to the Special Issue Halogen-Bonded Cocrystals)

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16 pages, 2056 KiB

Open AccessReview

Synthesis Methods and Favorable Conditions for Spherical Vaterite Precipitation: A Review

by Donata Konopacka-Łyskawa

Crystals 2019, 9(4), 223; https://doi.org/10.3390/cryst9040223 - 25 Apr 2019

Cited by 107 | Viewed by 9152

Abstract

Vaterite is the least thermodynamically stable anhydrous calcium carbonate polymorph. Its existence is very rare in nature, e.g., in some rock formations or as a component of biominerals produced by some fishes, crustaceans, or birds. Synthetic vaterite particles are proposed as carriers of [...] Read more.

Vaterite is the least thermodynamically stable anhydrous calcium carbonate polymorph. Its existence is very rare in nature, e.g., in some rock formations or as a component of biominerals produced by some fishes, crustaceans, or birds. Synthetic vaterite particles are proposed as carriers of active substances in medicines, additives in cosmetic preparations as well as adsorbents. Also, their utilization as a pump for microfluidic flow is also tested. In particular, vaterite particles produced as polycrystalline spheres have large potential for application. Various methods are proposed to precipitate vaterite particles, including the conventional solution-solution synthesis, gas-liquid method as well as special routes. Precipitation conditions should be carefully selected to obtain a high concentration of vaterite in all these methods. In this review, classical and new methods used for vaterite precipitation are presented. Furthermore, the key parameters affecting the formation of spherical vaterite are discussed. Full article

(This article belongs to the Special Issue Mineralogical Crystallography)

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12 pages, 3865 KiB

Open AccessArticle

Synthesis, Crystal Structure, Thermal Analysis, and DFT Calculations of Molecular Copper(II) Chloride Complexes with Bitopic Ligand 1,1,2,2-tetrakis(pyrazol-1-yl)ethane

by Elizaveta Lider, Taisiya Sukhikh, Anton Smolentsev, Evgeny Semitut, Evgeny Filatov and Andrei Potapov

Crystals 2019, 9(4), 222; https://doi.org/10.3390/cryst9040222 - 24 Apr 2019

Cited by 1 | Viewed by 4532

Abstract

Two binuclear coordination compounds of Cu(II) chloride with the bitopic ligand 1,1,2,2-tetrakis(pyrazol-1-yl)ethane (Pz⁴) of the composition [Cu₂(µ₂-Pz⁴)(DMSO)₂Cl₄]·4H₂O and [Cu₂(µ₂-Pz⁴)(DMSO)₂Cl₄]∙2DMSO [...] Read more.

Two binuclear coordination compounds of Cu(II) chloride with the bitopic ligand 1,1,2,2-tetrakis(pyrazol-1-yl)ethane (Pz⁴) of the composition [Cu₂(µ₂-Pz⁴)(DMSO)₂Cl₄]·4H₂O and [Cu₂(µ₂-Pz⁴)(DMSO)₂Cl₄]∙2DMSO were prepared and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, single-crystal X-ray diffraction, and powder diffraction analysis. It was shown that in contrast to silver(I) and copper(II) nitrates, copper(II) chloride forms discrete complexes instead of coordination polymers. The supramolecular structure of the complex [Cu₂(µ₂-Pz⁴)(DMSO)₂Cl₄]·4H₂O with lattice water molecules is formed by OH···Cl and OH···O hydrogen bonds. Density functional theory (DFT) calculations of vibrational frequencies of the ligand and its copper(II) complex allowed for assigning IR bands to specific vibrations. Full article

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9 pages, 3196 KiB

Open AccessArticle

Reconfigurable Topological Phases in Two-Dimensional Dielectric Photonic Crystals

by Hongbo Huang, Shaoyong Huo and Jiujiu Chen

Crystals 2019, 9(4), 221; https://doi.org/10.3390/cryst9040221 - 24 Apr 2019

Cited by 23 | Viewed by 4825

Abstract

The extensive research on photonic topological insulators has opened up an intriguing way to control electromagnetic (EM) waves. In this work, we numerically demonstrate reconfigurable microwave photon analogues of topological insulator (TIs) in a triangular lattice of elliptical cylinders, according to the theory [...] Read more.

The extensive research on photonic topological insulators has opened up an intriguing way to control electromagnetic (EM) waves. In this work, we numerically demonstrate reconfigurable microwave photon analogues of topological insulator (TIs) in a triangular lattice of elliptical cylinders, according to the theory of topological defects. Multiple topological transitions between the trivial and nontrivial photonic phases can be realized by inhomogeneously changing the ellipse orientation, without altering the lattice structure. Topological protection of the edge states and reconfigurable topological one-way propagation at microwave frequencies, are further verified. Our approach provides a new route towards freely steering light propagations in dielectric photonic crystals (PCs), which has potential applications in the areas of topological signal processing and sensing. Full article

(This article belongs to the Special Issue Recent Advances in Novel Topological Materials)

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16 pages, 6683 KiB

Open AccessReview

Laser Performance of Neodymium- and Erbium-Doped GYSGG Crystals

by Kai Zhong

Crystals 2019, 9(4), 220; https://doi.org/10.3390/cryst9040220 - 24 Apr 2019

Cited by 3 | Viewed by 4359

Abstract

Garnet crystals possess many properties that are desirable in laser host materials, e.g., they are suitable for diode laser (LD) pumping, stable, hard, optically isotropic, and have good thermal conductivity, permitting laser operation at high average power levels. Recently, a new garnet material, [...] Read more.

Garnet crystals possess many properties that are desirable in laser host materials, e.g., they are suitable for diode laser (LD) pumping, stable, hard, optically isotropic, and have good thermal conductivity, permitting laser operation at high average power levels. Recently, a new garnet material, GYSGG, was developed by replacing some of the yttrium ions (Y³⁺) with gadolinium ions (Gd³⁺) in YSGG, demonstrating great potential as a laser host material. GYSGG crystals doped with trivalent neodymium ion (Nd³⁺) and erbium ions (Er³⁺) were successfully grown for laser generation in the near- and mid-infrared range, with some of the laser performances reaching the level of mature laser gain media. This paper gives an overview of the achievements made in Nd³⁺- and Er³⁺-doped GYSGG lasers at different wavelength ranges. Additionally, full descriptions on Q-switching, mode-locking and wavelength-selecting methods for Nd:GYSGG, and the mechanisms of power scaling by co-doping sensitizers and deactivators in Er:GYSGG, are given. It is expected that this review will help researchers from related areas to quickly gain an understanding of these laser materials and promotes their commercialization and applications. Full article

(This article belongs to the Special Issue Laser Crystals)

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12 pages, 3912 KiB

Open AccessArticle

Assembly of Imidazolyl-Substituted Nitronyl Nitroxides into Ferromagnetically Coupled Chains

by Vasily Romanov, Irina Bagryanskaya, Nina Gritsan, Dmitry Gorbunov, Yulia Vlasenko, Mehman Yusubov, Elena Zaytseva, Dominique Luneau and Evgeny Tretyakov

Crystals 2019, 9(4), 219; https://doi.org/10.3390/cryst9040219 - 23 Apr 2019

Cited by 8 | Viewed by 3879

Abstract

New nitronyl nitroxides, namely, 2-(4,5-dimethylimidazol-2-yl)- and 2-(4,5-dichloroimidazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-3-oxide-1-oxyl, were prepared in crystalline form. According to single-crystal X-ray data, intra- and intermolecular hydrogen bonds are formed between NH groups of the imidazole cycles and O atoms of the nitroxide moieties. The intermolecular H-bonds [...] Read more.

New nitronyl nitroxides, namely, 2-(4,5-dimethylimidazol-2-yl)- and 2-(4,5-dichloroimidazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-3-oxide-1-oxyl, were prepared in crystalline form. According to single-crystal X-ray data, intra- and intermolecular hydrogen bonds are formed between NH groups of the imidazole cycles and O atoms of the nitroxide moieties. The intermolecular H-bonds contribute to the alignment of molecules into chains along the a-axis; this alignment causes short intrachain contacts between O and C atoms carrying spin density of opposite signs. Such an arrangement of nitroxides induces ferromagnetic intrachain interactions (J ≈ 10 cm⁻¹) between neighboring radicals. Full article

(This article belongs to the Special Issue Novel Hydrogen-bonded Materials with Significant Physical Properties)

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10 pages, 5157 KiB

Open AccessArticle

Controlled Two-Step Formation of Faceted Perovskite Rare-Earth Scandate Nanoparticles

by Ryan J. Paull, Tiffany Ly, Zachary R. Mansley, Kenneth R. Poeppelmeier and Laurence D. Marks

Crystals 2019, 9(4), 218; https://doi.org/10.3390/cryst9040218 - 23 Apr 2019

Cited by 8 | Viewed by 4091

Abstract

A general approach to the formation of well-faceted nanoparticles is discussed and successfully applied to the production of several rare-earth scandates. Two steps were used, with higher temperatures first to nucleate the perovskite phase, followed by lower temperatures to smooth the particle surfaces. [...] Read more.

A general approach to the formation of well-faceted nanoparticles is discussed and successfully applied to the production of several rare-earth scandates. Two steps were used, with higher temperatures first to nucleate the perovskite phase, followed by lower temperatures to smooth the particle surfaces. Exploiting these two different regimes led to smaller nanoparticles with more faceting. This general approach may be tailored to other material systems as a step towards producing shape-controlled nanoparticles for a desired application. Full article

(This article belongs to the Special Issue Rare-Earth Metal Compounds)

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15 pages, 3278 KiB

Open AccessArticle

Numerical Simulation of Thermal-Solutal Capillary-Buoyancy Flow of Ge_1–xSi_x Single Crystals Driven by Surface-Tension and Rotation in a Czochralski Configuration

by Jia-Jia Yu, Lu Zhang, Ting Shen, Li Zhang and You-Rong Li

Crystals 2019, 9(4), 217; https://doi.org/10.3390/cryst9040217 - 22 Apr 2019

Cited by 3 | Viewed by 2862

Abstract

A series of three-dimensional numerical simulations were performed to understand the thermal-solutal capillary-buoyancy flow of Ge_1-xSi_x melts during Czochralski crystal growth with a rotating crystal or crucible. The crystal and crucible rotation Reynolds numbers in this work are 0∼3.5 × [...] Read more.

A series of three-dimensional numerical simulations were performed to understand the thermal-solutal capillary-buoyancy flow of Ge_1-xSi_x melts during Czochralski crystal growth with a rotating crystal or crucible. The crystal and crucible rotation Reynolds numbers in this work are 0∼3.5 × 10³ (0∼4.4 rpm) and 0∼−2.4 × 10³ (0∼−1.5 rpm), respectively. Simulation results show that if the thermal capillary Reynolds number is relatively low, the flow will be steady and axisymmetric, even though the crystal or crucible rotates at a constant rate. The critical thermal capillary Reynolds number for the initiation of the three-dimensional oscillatory flow is larger than that of pure fluids. As the crystal or crucible rotation rate increases, the critical thermal capillary Reynolds number first increases and then decreases. The dominant flow pattern after the flow destabilization is azimuthal traveling waves. Furthermore, a reversed evolution from the oscillatory spoke pattern to traveling waves appears in the melt. Once the crystal or crucible rotation rate is relatively large, the traveling waves respectively evolve to rotating waves at the crystal rotation and a spindle-like pattern at the crucible rotation. In addition, the maximum amplitude of solute concentration oscillation on the free surface initially decreases, but finally rises with the crystal or crucible rotation rate increasing. Full article

(This article belongs to the Section Crystal Engineering)

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9 pages, 2861 KiB

Open AccessArticle

Direct Amplification of High Energy Pulsed Laser in Fiber-Single Crystal Fiber with High Average Power

by Feng Li, Zhi Yang, Zhiguo Lv, Yang Yang, Yishan Wang, Xiaojun Yang, Wei Zhao, Qianglong Li and Yufeng Wei

Crystals 2019, 9(4), 216; https://doi.org/10.3390/cryst9040216 - 21 Apr 2019

Cited by 4 | Viewed by 3811

Abstract

A laser master oscillator power amplifier (MOPA) system consisting of a fiber amplifier and a two-stage Yb:YAG single crystal fiber (SCF) is experimentally studied. The nonlinear stimulated Raman scattering (SRS) is avoided by limiting the output power of the fiber preamplifier to 600 [...] Read more.

A laser master oscillator power amplifier (MOPA) system consisting of a fiber amplifier and a two-stage Yb:YAG single crystal fiber (SCF) is experimentally studied. The nonlinear stimulated Raman scattering (SRS) is avoided by limiting the output power of the fiber preamplifier to 600 mW. Due to the benefit from the low nonlinearity and high amplification gain of the SCF, a laser pulse duration of 16.95 ps and a high average power of 41.7 W at a repetition rate of 250 kHz are obtained by using a two-stage polarization controlled double-pass amplification of Yb:YAG SCF, corresponding to an output energy of 166.8 μJ and a peak power of 9.84 MW, respectively. The polarization controlled SCF amplification scheme achieved a gain as high as more than 69 times. During the amplification, the spectra gain narrowing effect and the polarization controlled four-pass amplification setup are also studied. The laser spectrum is narrowed from over 10 nm to less than 3 nm, and the pulse width is also compressed to hundreds of femtosecond by dechirping the laser pulse. This compact-sized, cost-effective laser source can be used in laser micromachining, or as the seeder source for generating much higher power and energy laser for scientific research. For some applications which need femtosecond laser, this laser source can also be compressed to femtosecond regime. Full article

(This article belongs to the Special Issue Laser Crystals)

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17 pages, 5398 KiB

Open AccessArticle

An Optical Microscope Study of the Morphology of Xenon Hydrate Crystals: Exploring New Approaches to Cryopreservation

by Alexey Kobelev, Valery Yashin, Nikita Penkov, Nikolay Shvirst, Mikhail Goltyaev, Anatoliy Kovtun and Eugeny Fesenko, Jr.

Crystals 2019, 9(4), 215; https://doi.org/10.3390/cryst9040215 - 20 Apr 2019

Cited by 5 | Viewed by 3560

Abstract

One of the possible approaches to a new method of cryopreservation seems to be the controlled formation of a multitude of small crystals in an object, which, due to their size, will not damage cellular structures. Managing the crystal formation, given the stochastic [...] Read more.

One of the possible approaches to a new method of cryopreservation seems to be the controlled formation of a multitude of small crystals in an object, which, due to their size, will not damage cellular structures. Managing the crystal formation, given the stochastic nature of the process, is an extremely difficult task. Theoretically, it is simplified if there is a sufficient number of changeable physical parameters, affecting the process. From this point of view, the use of ice-like gas hydrates for the purposes of cryopreservation seems to be a promising option. We investigated the process of growth of xenon gas hydrates via standard microscopy under different conditions using the specialized optical cell for observation at elevated pressures. The formation of crystals was observed in the system “supercooled liquid–xenon–water vapor” at negative, near-zero and positive values of temperature, and pressure of xenon up to 8 atmospheres. The morphology of xenon hydrate crystals observed in the experiments was analyzed and classified into five categories. The influence of physical conditions on the predominant crystal morphology was also studied. We found no evidence that the possible damaging effect of hydrate crystals should be less severe than of ice crystals. Full article

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12 pages, 2369 KiB

Open AccessArticle

Ion Transport Behavior through Thermally Reduced Graphene Oxide Membrane for Precise Ion Separation

by Peizhuo Hu, Bochen Huang, Quanduo Miao, Haijing Wang, Lian Liu, Wenya Tai, Tonghuan Liu, Zhan Li, Suwen Chen and Lijuan Qian

Crystals 2019, 9(4), 214; https://doi.org/10.3390/cryst9040214 - 20 Apr 2019

Cited by 7 | Viewed by 4016

Abstract

The cation transport behavior of thermally treated reduced graphene oxide membranes (GOMs) is reported. The GOMs were reduced by heat treatment at 25, 80, and 120 °C and then characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction, and X-ray photoelectron spectroscopy to [...] Read more.

The cation transport behavior of thermally treated reduced graphene oxide membranes (GOMs) is reported. The GOMs were reduced by heat treatment at 25, 80, and 120 °C and then characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction, and X-ray photoelectron spectroscopy to determine oxygen group content, C/O ratio, and layer spacing. The permeation rates of various cations with different sizes and charge numbers through these membranes were measured to understand the effect of the cations on transport behavior. The results indicated that the cation transport through the membranes depended on the layer spacing of the membrane and ion size and charge. Cations of the same valence permeating through the same GOM could be differentiated by their hydration radius, whereas the same type of cation passing through different GOMs could be determined by the spacing of the GOM layers. The cation valence strongly affected permeation behavior. The GOM that was prepared at 120 °C exhibited a narrow layer spacing and high separation factors for Mg/Ca, Mg/Sr, K/Ca, and K/Fe. The cations moving through the membrane could insert into the membrane lamellas, which neutralized the negative charge of the membrane, enlarged the layer spacing of the GOMs, and affected cation permeation. Full article

(This article belongs to the Special Issue Inorganic Layered Crystals: From Fundamentals to Materials Performance)

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13 pages, 3250 KiB

Open AccessArticle

Morphological Monte Carlo Simulation for Crystallization of Isotactic Polypropylene in a Temperature Gradient

by Chunlei Ruan

Crystals 2019, 9(4), 213; https://doi.org/10.3390/cryst9040213 - 20 Apr 2019

Cited by 4 | Viewed by 3737

Abstract

Polymers are poor heat conductors, so the cooling of thick-walled shapes results in temperature gradients. Here, isotactic polypropylene (iPP) is chosen as a model polymer for the study of polymer crystallization in a temperature gradient field. The morphological Monte Carlo algorithm is applied, [...] Read more.

Polymers are poor heat conductors, so the cooling of thick-walled shapes results in temperature gradients. Here, isotactic polypropylene (iPP) is chosen as a model polymer for the study of polymer crystallization in a temperature gradient field. The morphological Monte Carlo algorithm is applied, combined with the radius growth model, to predict the growth of spherulites. Through comparison of the two numerical solutions, analytical solution and experimental data, the validity of the morphological Monte Carlo algorithm is demonstrated. In addition, the roles of central temperature, temperature gradient for the evolution of spherulites, and the conversion degree of the melt into spherulites are considered. The results of the study show that increases in central temperature and temperature gradient can increase the anisotropy of spherulites. Isothermal crystallization and crystallization in a temperature gradient field are compared, and the differences are considered. Results show that when the central temperature is below 125 °C, and when the temperature gradients are less than 15 K/mm and 27 K/mm, the differences in the conversion degree of the melt into spherulites are less than 2% and 5%, respectively. Therefore, crystallization under such temperature gradient conditions can be simplified as isothermal crystallization. Full article

(This article belongs to the Special Issue Microstructure Evolutions and Mechanical Behavior of Semicrystalline Polymers)

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11 pages, 537 KiB

Open AccessArticle

Field-Angle Dependence of Interlayer Magnetoresistance in Organic Dirac Electron System α-(BEDT-TTF)₂I₃

by Takehiro Tani, Naoya Tajima and Akito Kobayashi

Crystals 2019, 9(4), 212; https://doi.org/10.3390/cryst9040212 - 19 Apr 2019

Cited by 6 | Viewed by 2845

Abstract

The effect of the Coulomb interaction in interlayer magnetoresistance is elucidated in collaboration with theory and experiments for the Dirac electron system in organic conductor

α

-(BEDT-TTF)

_{2}

I

_{3}

under a strong magnetic field. It is found that the effective g-factor [...] Read more.

The effect of the Coulomb interaction in interlayer magnetoresistance is elucidated in collaboration with theory and experiments for the Dirac electron system in organic conductor

α

-(BEDT-TTF)

_{2}

I

_{3}

under a strong magnetic field. It is found that the effective g-factor enhanced by Coulomb interaction depends on the angle of the magnetic field, resulting in the field-angle dependence of a characteristic magnetic field in which interlayer resistance has a minimum due to spin splitting

N = 0

Landau levels. The qualitative agreement between the theory and experimental results for the field-angle dependence of interlayer magnetoresistance is obtained. Full article

(This article belongs to the Special Issue Synthesis and Characterization of New Superconductors Materials)

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17 pages, 9863 KiB

Open AccessArticle

Single-Crystal Growth of Metallic Rare-Earth Tetraborides by the Floating-Zone Technique

by Daniel Brunt, Monica Ciomaga Hatnean, Oleg A. Petrenko, Martin R. Lees and Geetha Balakrishnan

Crystals 2019, 9(4), 211; https://doi.org/10.3390/cryst9040211 - 19 Apr 2019

Cited by 10 | Viewed by 4673

Abstract

The rare-earth tetraborides are exceptional in that the rare-earth ions are topologically equivalent to the frustrated Shastry-Sutherland lattice. In this paper, we report the growth of large single crystals of RB

_{4}

(where R = Nd, Gd → Tm, and Y) by [...] Read more.

The rare-earth tetraborides are exceptional in that the rare-earth ions are topologically equivalent to the frustrated Shastry-Sutherland lattice. In this paper, we report the growth of large single crystals of RB

_{4}

(where R = Nd, Gd → Tm, and Y) by the floating-zone method, using a high-power xenon arc-lamp furnace. The crystal boules have been characterized and tested for their quality using X-ray diffraction techniques and temperature- and field-dependent magnetization and AC resistivity measurements. Full article

(This article belongs to the Special Issue Optical Floating Zone and Crystals Grown by this Method)

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18 pages, 3431 KiB

Open AccessArticle

The High Pressure Behavior of Galenobismutite, PbBi₂S₄: A Synchrotron Single Crystal X-ray Diffraction Study

by Paola Comodi, Azzurra Zucchini, Tonci Balić-Žunić, Michael Hanfland and Ines Collings

Crystals 2019, 9(4), 210; https://doi.org/10.3390/cryst9040210 - 18 Apr 2019

Cited by 4 | Viewed by 3127

Abstract

High-pressure single-crystal synchrotron X-ray diffraction data for galenobismutite, PbBi₂S₄ collected up to 20.9 GPa, were fitted by a third-order Birch-Murnaghan equation of state, as suggested by a F_E-f_E plot, yielding V₀ = 697.4(8) Å³ [...] Read more.

High-pressure single-crystal synchrotron X-ray diffraction data for galenobismutite, PbBi₂S₄ collected up to 20.9 GPa, were fitted by a third-order Birch-Murnaghan equation of state, as suggested by a F_E-f_E plot, yielding V₀ = 697.4(8) Å³, K₀ = 51(1) GPa and K’ = 5.0(2). The axial moduli were M_0a = 115(7) GPa and M_a’ = 28(2) for the a axis, M_0b = 162(3) GPa and M_b’ = 8(3) for the b axis, M_0c = 142(8) GPa and M_c’ = 26(2) for the c axis, with refined values of a₀, b₀, c₀ equal to 11.791(7) Å, 14.540(6) Å 4.076(3) Å, respectively, and a ratio equal to M_0a:M_0b:M_0c = 1.55:1:1.79. The main structural changes on compression were the M2 and M3 (occupied by Bi, Pb) movements toward the centers of their respective trigonal prism bodies and M3 changes towards CN8. The M1 site, occupied solely by Bi, regularizes the octahedral form with CN6. The eccentricities of all cation sites decreased with compression testifying for a decrease in stereochemical expression of lone electron pairs. Galenobismutite is isostructural with calcium ferrite CaFe₂O₄, the suggested high pressure structure can host Na and Al in the lower mantle. The study indicates that pressure enables the incorporation of other elements in this structure, increasing its potential significance for mantle mineralogy. Full article

(This article belongs to the Special Issue Mineralogical Crystallography)

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11 pages, 594 KiB

Open AccessArticle

Analytic Solutions to Two-Dimensional Decagonal Quasicrystals with Defects Using Complex Potential Theory

by Haobai Cao, Yiqing Shi and Wu Li

Crystals 2019, 9(4), 209; https://doi.org/10.3390/cryst9040209 - 17 Apr 2019

Cited by 1 | Viewed by 2757

Abstract

An analytical treatment for two-dimensional point group 10 mm decagonal quasicrystals with defects was suggested based on the complex potential method. On the basis of the assumption of linear elasticity, two new conformal maps were applied to two examples: the first was an [...] Read more.

An analytical treatment for two-dimensional point group 10 mm decagonal quasicrystals with defects was suggested based on the complex potential method. On the basis of the assumption of linear elasticity, two new conformal maps were applied to two examples: the first was an arc with an elliptic notch inner surface in a decagonal quasicrystal, where the complex potentials could be exactly obtained; and the second was concerned with a decagonal point group 10 mm quasicrystalline strip weakened by a Griffith crack, which was subjected to a pair of uniform static pressures. Using the basic idea underlying crack theory, the extent of the stress intensity factors was analytically estimated. If the height was allowed to approach infinity, these results can be turned into the known results of an “ordinary” crystal with only phonon elastic parameters when the phason and phonon-phason elastic constants are eliminated. Full article

(This article belongs to the Special Issue Structure and Properties of Quasicrystals)

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13 pages, 3355 KiB

Open AccessArticle

Synthesis and Biological Evaluations of a Novel Oxidovanadium(IV) Adenosine Monophosphate Complex as Anti-Diabetic Agent

by Ahmed M. Naglah, Mohamed A. Al-Omar, Mashooq A. Bhat, Asma S. Al-Wasidi, Amnah M. A. Alsuhaibani, Akram M. El-Didamony, Nader Hassan, Sameh Abo Taleb and Moamen S. Refat

Crystals 2019, 9(4), 208; https://doi.org/10.3390/cryst9040208 - 15 Apr 2019

Cited by 4 | Viewed by 2927

Abstract

In the present study, a novel [(AMP)(VO)(H₂O)₂] complex was formed through chemical reactions between oxidovanadium(IV)sulfate and adenosine monophosphate. This complex was characterized using various analyses, including microanalytical, molar conductivity, spectroscopic (solid reflectance and FTIR), magnetic susceptibility, thermogravimetric (TGA), X-ray [...] Read more.

In the present study, a novel [(AMP)(VO)(H₂O)₂] complex was formed through chemical reactions between oxidovanadium(IV)sulfate and adenosine monophosphate. This complex was characterized using various analyses, including microanalytical, molar conductivity, spectroscopic (solid reflectance and FTIR), magnetic susceptibility, thermogravimetric (TGA), X-ray powder diffraction (XRD), and scanning (SEM) and transmission (TEM) electron microscopy. The in vivo antidiabetic activity of the oxidovanadium(IV) complex was determined using streptozotocin-induced rats. The results suggested that the synthesized complex can be used as an antidiabetic agent based on the observed biochemical effects. Full article

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10 pages, 3121 KiB

Open AccessArticle

Growth and Property Investigations of Two Organic–Inorganic Hybrid Molecular Crystals with High Thermal Stability: 4-Iodoanilinium perchlorate 18-crown-6 and 4-Iodoanilinium Borofluorate 18-crown-6

by Lihui Zhang, Tiantian Kang, Fanghua Zhao, Duanliang Wang, Chuanying Shen and Jiyang Wang

Crystals 2019, 9(4), 207; https://doi.org/10.3390/cryst9040207 - 15 Apr 2019

Cited by 5 | Viewed by 3095

Abstract

Two new organic–inorganic hybrid molecular single crystals, 4-Iodoanilinium perchlorate 18-crown-6 (1) and 4-Iodoanilinium borofluorate 18-crown-6 (2), with large sizes and high thermal stability were successfully synthesized by solution method. Their structures, phase purities, thermal stability, dielectric, absorption and fluorescence [...] Read more.

Two new organic–inorganic hybrid molecular single crystals, 4-Iodoanilinium perchlorate 18-crown-6 (1) and 4-Iodoanilinium borofluorate 18-crown-6 (2), with large sizes and high thermal stability were successfully synthesized by solution method. Their structures, phase purities, thermal stability, dielectric, absorption and fluorescence spectra were systematically investigated for potential applications. Compounds 1 and 2 crystallize in orthorhombic crystal system, in same space group, namely Pnma. The thermal measurements shown 1 and 2 maintain high thermal stability up to 150 °C. The temperature dependency of dielectric constant was studied, and no distinct anomaly was observed. The band gap were calculated to be 3.38 eV and 3.57 eV for 1 and 2, respectively, slightly smaller than those of layer perovskite (benzylammonium)₂PbCl₄ semiconducting materials, which have potential applications in optoelectronic detection field. The investigations throw light on the semiconductor properties of organic–inorganic hybrid crown type material and provide two types of crown compounds with high thermal stability. Full article

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11 pages, 4319 KiB

Open AccessEditor’s ChoiceArticle

Dielectric and Piezoelectric Properties of Textured Lead-Free Na_0.5Bi_0.5TiO₃-Based Ceramics

by Nannan Dong, Xiaoyi Gao, Fangquan Xia, Hanxing Liu, Hua Hao and Shujun Zhang

Crystals 2019, 9(4), 206; https://doi.org/10.3390/cryst9040206 - 14 Apr 2019

Cited by 24 | Viewed by 4202

Abstract

This work provides a comparative study of the dielectric and piezoelectric properties of randomly oriented and textured 0.88Na_0.5Bi_0.5TiO₃-0.08K_0.5Bi_0.5TiO₃-0.04BaTiO₃ (88NBT) ceramics. Textured ceramics were fabricated by template grain growth (TGG) method [...] Read more.

This work provides a comparative study of the dielectric and piezoelectric properties of randomly oriented and textured 0.88Na_0.5Bi_0.5TiO₃-0.08K_0.5Bi_0.5TiO₃-0.04BaTiO₃ (88NBT) ceramics. Textured ceramics were fabricated by template grain growth (TGG) method using NaNbO₃ (NN) for templates. For textured ceramics with 4 wt% NN templates, a Lotgering factor of 96% and piezoelectric coefficient d₃₃ of 185 pC/N were obtained. Compared to the randomly oriented ceramics, textured ceramics show lower strain hysteresis (H = 7.6%), higher unipolar strain of 0.041% with corresponding large signal piezoelectric coefficient d₃₃^* of 200 pm/V at applied field of 2 kV/mm. This enhancement can be explained by the grain orientation along <001> direction by texturing, where an engineered domain configuration is formed after polarization, leading to decreased hysteresis and increased piezoelectric property. Full article

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12 pages, 4034 KiB

Open AccessArticle

Kinetics of Non-Isothermal and Isothermal Crystallization in a Liquid Crystal with Highly Ordered Smectic Phase as Reflected by Differential Scanning Calorimetry, Polarized Optical Microscopy and Broadband Dielectric Spectroscopy

by Małgorzata Jasiurkowska-Delaporte, Tomasz Rozwadowski and Ewa Juszyńska-Gałązka

Crystals 2019, 9(4), 205; https://doi.org/10.3390/cryst9040205 - 12 Apr 2019

Cited by 24 | Viewed by 5049

Abstract

The kinetics of the non-isothermal and isothermal crystallization of the crystalline smectic B phase (soft crystal B, SmB_cr) in 4-n-butyloxybenzylidene-4′-n′-octylaniline (BBOA) was studied by a combination of differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS) and polarized optical microscopy (POM). On [...] Read more.

The kinetics of the non-isothermal and isothermal crystallization of the crystalline smectic B phase (soft crystal B, SmB_cr) in 4-n-butyloxybenzylidene-4′-n′-octylaniline (BBOA) was studied by a combination of differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS) and polarized optical microscopy (POM). On cooling, part of the SmB_cr phase undergoes conversion to a crystalline phase and the remainder forms a glassy state; after the glass softens, crystallization is completed during subsequent heating. By analyzing the area of the crystal growing in the texture of SmB_cr as a function of time, the evolution of degree of crystallinity, D(t), was estimated. It was demonstrated that upon heating, D(t) follows the same Avrami curve as the crystallization during cooling. Non-isothermal crystallization observed during slow cooling rates (3K/min ≤ ϕ ≤ 5K/min) is a thermodynamically-controlled process with the energy barrier Ea ≈ 175 kJ/mol; however, the crystallization occurring during fast cooling (5 K/min > ϕ ≥ 30K/min) is driven by a diffusion mechanism, and is characterized by E_a ≈ 305 kJ/mol. The isothermal crystallization taking place in the temperature range 274 K and 281 K is determined by nucleus formation. Full article

(This article belongs to the Section Liquid Crystals)

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7 pages, 1213 KiB

Open AccessArticle

Passivation Mechanism of Nitrogen in ZnO under Different Oxygen Ambience

by Xingyou Chen, Zhenzhong Zhang, Yunyan Zhang, Bin Yao, Binghui Li and Qian Gong

Crystals 2019, 9(4), 204; https://doi.org/10.3390/cryst9040204 - 12 Apr 2019

Cited by 4 | Viewed by 2870

Abstract

Nitrogen-doped ZnO thin films were grown on a-plane Al₂O₃ by plasma-assisted molecular beam epitaxy. Hall-effect measurements indicated that the nitrogen-doped ZnO films showed p-type behavior first, then n-type, with the growth conditions changing from oxygen-radical-rich to oxygen-radical-deficient ambience, accompanied with [...] Read more.

Nitrogen-doped ZnO thin films were grown on a-plane Al₂O₃ by plasma-assisted molecular beam epitaxy. Hall-effect measurements indicated that the nitrogen-doped ZnO films showed p-type behavior first, then n-type, with the growth conditions changing from oxygen-radical-rich to oxygen-radical-deficient ambience, accompanied with the increase of the N/O ratio in the plasmas. The increasing green emission in the low temperature photoluminescence spectra, related to single ionized oxygen vacancy in ZnO, was ascribed to the decrease of active oxygen atoms in the precursor plasmas. CN complex, a donor defect with low formation energy, was demonstrated to be easily introduced into ZnO under O-radical-deficient ambience, which compensated the nitrogen-related acceptor, along with the oxygen vacancy. Full article

(This article belongs to the Special Issue Zinc Oxide Nanomaterials and Based Devices)

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9 pages, 2106 KiB

Open AccessArticle

A Novel Liquid Packaging Structure of Deep-Ultraviolet Light-Emitting Diodes to Enhance the Light-Extraction Efficiency

by Chieh-Yu Kang, Chih-Hao Lin, Tingzhu Wu, Po-Tsung Lee, Zhong Chen and Hao-Chung Kuo

Crystals 2019, 9(4), 203; https://doi.org/10.3390/cryst9040203 - 12 Apr 2019

Cited by 21 | Viewed by 4890

Abstract

To realize high-efficiency, AlGaN-based, deep-ultraviolet light-emitting diodes (DUV-LEDs), enhancing their light-extraction efficiency and reducing thermal resistance is very crucial. We proposed a liquid packaging structure that could enhance optical power by 27.2% and 70.7% for flat type and lens type 281-nm DUV-LEDs, respectively. [...] Read more.

To realize high-efficiency, AlGaN-based, deep-ultraviolet light-emitting diodes (DUV-LEDs), enhancing their light-extraction efficiency and reducing thermal resistance is very crucial. We proposed a liquid packaging structure that could enhance optical power by 27.2% and 70.7% for flat type and lens type 281-nm DUV-LEDs, respectively. A significant improvement effect at different wavelengths, such as 268 nm and 310 nm, was also observed. Furthermore, using the liquid packaging structure, the thermal resistance was reduced by 30.3% compared to the conventional structure. Finally, the reliability of liquid packaging DUV-LEDs was tested. The light output maintenance of liquid packaging DUV-LEDs was compared to the conventional structure. Full article

(This article belongs to the Special Issue GaN-Based Optoelectronic Materials and Light Emitting Devices)

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9 pages, 8552 KiB

Open AccessArticle

Ultra-High Light Extraction Efficiency and Ultra-Thin Mini-LED Solution by Freeform Surface Chip Scale Package Array

by Che-Hsuan Huang, Chieh-Yu Kang, Shu-Hsiu Chang, Chih-Hao Lin, Chun-Yu Lin, Tingzhu Wu, Chin-Wei Sher, Chien-Chung Lin, Po-Tsung Lee and Hao-Chung Kuo

Crystals 2019, 9(4), 202; https://doi.org/10.3390/cryst9040202 - 11 Apr 2019

Cited by 24 | Viewed by 5796

Abstract

In this study, we present a novel type of package, freeform-designed chip scale package (FDCSP), which has ultra-high light extraction efficiency and bat-wing light field. For the backlight application, mainstream solutions are chip-scale package (CSP) and surface-mount device package (SMD). Comparing with these [...] Read more.

In this study, we present a novel type of package, freeform-designed chip scale package (FDCSP), which has ultra-high light extraction efficiency and bat-wing light field. For the backlight application, mainstream solutions are chip-scale package (CSP) and surface-mount device package (SMD). Comparing with these two mainstream types of package, the light extraction efficiency of CSP, SMD, and FDCSP are 88%, 60%, and 96%, respectively. In addition to ultra-high light extraction efficiency, because of the 160-degree bat-wing light field, FDCSP could provide a thinner and low power consumption mini-LED solution with a smaller number of LEDs than CSP and SMD light source array. Full article

(This article belongs to the Special Issue GaN-Based Optoelectronic Materials and Light Emitting Devices)

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7 pages, 3115 KiB

Open AccessArticle

High Stability LED-Pumped Nd:YVO₄ Laser with a Cr:YAG for Passive Q-Switching

by Hong Xiao, Tianzhuo Zhao, Wenqi Ge, Qixiu Zhong, Mingshan Li, Jiaqi Yu, Zhongwei Fan, Shengwei Bian and Yanzhong Chen

Crystals 2019, 9(4), 201; https://doi.org/10.3390/cryst9040201 - 10 Apr 2019

Cited by 5 | Viewed by 5892

Abstract

With improvements in light-emitting diode (LED) performance and a sharp decline in price, a light source with the irradiance of a laser and the cost of an LED is worthy of further study. We demonstrated a LED-pumped Nd:YVO₄ laser in quasi-continuous-wave (QCW) [...] Read more.

With improvements in light-emitting diode (LED) performance and a sharp decline in price, a light source with the irradiance of a laser and the cost of an LED is worthy of further study. We demonstrated a LED-pumped Nd:YVO₄ laser in quasi-continuous-wave (QCW) and passively Q-switched (PQS) regime. With an incident pump energy of 6.28 mJ (150 μs pulses at 1 Hz), the Nd:YVO₄ laser has an energy of 206 μJ at 1064 nm in the QCW regime. The optical conversion efficiency of the system is 4.1%, and the slope efficiency is 9.0%. A pulsed energy of 2.5 μJ was obtained with a duration of 897 ns (FWHM) in the PQS regime, which means the peak power is 2.79 W. The output energy stability is 97.54%. Full article

(This article belongs to the Special Issue Recent Advances in Light-Emitting Diodes (LEDs))

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17 pages, 2723 KiB

Open AccessArticle

Decomposition Characterizations of Methane Hydrate Confined inside Nanoscale Pores of Silica Gel below 273.15 K

by Lihua Wan, Xuebing Zhou, Peili Chen, Xiaoya Zang, Deqing Liang and Jinan Guan

Crystals 2019, 9(4), 200; https://doi.org/10.3390/cryst9040200 - 10 Apr 2019

Cited by 11 | Viewed by 3906

Abstract

The formation and decomposition of gas hydrates in nanoscale sediments can simulate the accumulation and mining process of hydrates. This paper investigates the Raman spectra of water confined inside the nanoscale pores of silica gel, the decomposition characterizations of methane hydrate that formed [...] Read more.

The formation and decomposition of gas hydrates in nanoscale sediments can simulate the accumulation and mining process of hydrates. This paper investigates the Raman spectra of water confined inside the nanoscale pores of silica gel, the decomposition characterizations of methane hydrate that formed from the pore water, and the intrinsic relationship between them. The results show that pore water has stronger hydrogen bonds between the pore water molecules at both 293 K and 223 K. The structure of pore water is conducive to the nucleation of gas hydrate. Below 273.15 K, the decomposition of methane hydrate formed from pore water was investigated at atmospheric pressure and at a constant volume vessel. We show that the decomposition of methane hydrate is accompanied by a reformation of the hydrate phase: The lower the decomposition temperature, the more times the reformation behavior occurs. The higher pre-decomposition pressure that the silica gel is under before decomposition is more favorable to reformation. Thus, reformation is the main factor in methane hydrate decomposition in nanoscale pores below 273.15 K and is attributed to the structure of pore water. Our results provide experimental data for exploring the control mechanism of hydrate accumulation and mining. Full article

(This article belongs to the Special Issue Ice Crystals)

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13 pages, 4552 KiB

Open AccessArticle

Sonochemical Synthesis of Cadmium(II) Coordination Polymer Nanospheres as Precursor for Cadmium Oxide Nanoparticles

by Farhad Akbari Afkhami, Ali Akbar Khandar, Ghodrat Mahmoudi, Reza Abdollahi, Atash V. Gurbanov and Alexander M. Kirillov

Crystals 2019, 9(4), 199; https://doi.org/10.3390/cryst9040199 - 9 Apr 2019

Cited by 7 | Viewed by 4387

Abstract

Nanospheres of a new coordination polymer {[Cd₂(µ-HL)(µ-L)(NO₃)₃(H₂O)]·H₂O}_n (1) were easily prepared by a sonochemical method from cadmium(II) nitrate and HL (HL, pyridine-2-carboxaldehyde isonicotinoyl hydrazone) in ethanol. Single crystals of 1 [...] Read more.

Nanospheres of a new coordination polymer {[Cd₂(µ-HL)(µ-L)(NO₃)₃(H₂O)]·H₂O}_n (1) were easily prepared by a sonochemical method from cadmium(II) nitrate and HL (HL, pyridine-2-carboxaldehyde isonicotinoyl hydrazone) in ethanol. Single crystals of 1 were also obtained using a branched tube method. The crystal structure of 1 indicates that the µ-HL/µ-L⁻ blocks act as linkers between the Cd(II) centers, assembling them into 1D tooth-shaped interdigitated chains, which are further interlinked into a complex 3D H-bonded network with a rare hms (3,5-conn) topology. Nanoparticles of 1 were characterized by elemental analysis, FT-IR spectroscopy, and powder X-ray diffraction (XPRD), while their spherical morphology was confirmed by transmission electron microscopy (TEM). Furthermore, in the presence of a surfactant, the thermolysis of sonochemically generated nanoparticles of 1 led to the formation of cadmium oxide nanospheres (cubic CdO) with an average diameter of 10 nm. This study extends the application of sonochemical synthetic methods for the generation of phase pure nanoparticles of coordination polymers and their thermolysis products. Full article

(This article belongs to the Section Crystal Engineering)

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9 pages, 2576 KiB

Open AccessArticle

Flexible Photonic Nanojet Formed by Cylindrical Graded-Index Lens

by Cheng-Yang Liu

Crystals 2019, 9(4), 198; https://doi.org/10.3390/cryst9040198 - 7 Apr 2019

Cited by 13 | Viewed by 4192

Abstract

Photonic nanojets formed in the vicinity of the cylindrical graded-index lens with different types of index grading are numerically investigated based on the finite-difference time-domain method. The cylindrical lens with 1600 nm diameter is assembled by eighty-seven hexagonally arranged close-contact nanofibers with 160 [...] Read more.

Photonic nanojets formed in the vicinity of the cylindrical graded-index lens with different types of index grading are numerically investigated based on the finite-difference time-domain method. The cylindrical lens with 1600 nm diameter is assembled by eighty-seven hexagonally arranged close-contact nanofibers with 160 nm diameter. Simulation and analysis results show that it is possible to engineer and elongate the photonic nanojet. Using differently graded-index nanofibers as building elements to compose this lens, the latitudinal and longitudinal sizes of the produced photonic nanojet can be flexibly adjusted. At an incident wavelength of 532 nm, the cylindrical lens with index grading = 2 can generate a photonic nanojet with a waist about 173 nm (0.32 wavelength). This lens could potentially contribute to the development of a novel device for breaking the diffraction limit in the field of optical nano-scope and bio-photonics. Full article

(This article belongs to the Special Issue Sonic and Photonic Crystals)

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7 pages, 1489 KiB

Open AccessArticle

Temperature Dependence of Raman Frequency Shift in SrWO₄ Crystal Studied by Lattice Dynamical Calculations

by Jun Suda and Petr G. Zverev

Crystals 2019, 9(4), 197; https://doi.org/10.3390/cryst9040197 - 7 Apr 2019

Cited by 7 | Viewed by 3593

Abstract

The frequency shift of the Raman modes in strontium tungstate (SrWO₄) was investigated in the temperature range from 15 to 295 K. The experimental temperature dependence of the shift was analyzed using both the lattice dynamical calculations and the lattice perturbative [...] Read more.

The frequency shift of the Raman modes in strontium tungstate (SrWO₄) was investigated in the temperature range from 15 to 295 K. The experimental temperature dependence of the shift was analyzed using both the lattice dynamical calculations and the lattice perturbative approach. We found that the quartic anharmonic term of the first-order perturbation and the cubic term of the second-order perturbation, as well as the thermal expansion, contribute to the temperature shift of the highest-frequency A_g(ν₁) mode. The values of the temperature sensitivity of the frequency shift of the Raman modes at room temperature were measured, which is important for developing high-power crystalline Raman lasers and frequency shifters. Full article

(This article belongs to the Special Issue Crystalline Raman Lasers)

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10 pages, 1421 KiB

Open AccessArticle

Crystal Growth of Quantum Magnets in the Rare-Earth Pyrosilicate Family R₂Si₂O₇ (R = Yb, Er) Using the Optical Floating Zone Method

by Harikrishnan S. Nair, Tim DeLazzer, Tim Reeder, Antony Sikorski, Gavin Hester and Kate A. Ross

Crystals 2019, 9(4), 196; https://doi.org/10.3390/cryst9040196 - 7 Apr 2019

Cited by 10 | Viewed by 4538

Abstract

We report on the crystal growth of rare-earth pyrosilicates,

R_{2}

Si

_{2}

O

_{7}

for R = Yb and Er using the optical floating zone method. The grown crystals comprise members from the family of pyrosilicates where the rare-earth atoms form a [...] Read more.

We report on the crystal growth of rare-earth pyrosilicates,

R_{2}

Si

_{2}

O

_{7}

for R = Yb and Er using the optical floating zone method. The grown crystals comprise members from the family of pyrosilicates where the rare-earth atoms form a distorted honeycomb lattice. C-Yb

_{2}

Si

_{2}

O

_{7}

is a quantum dimer magnet with field-induced long range magnetic order, while D-Er

_{2}

Si

_{2}

O

_{7}

is an Ising-type antiferromagnet. Both growths resulted in multi-crystal boules, with cracks forming between the different crystal orientations. The Yb

_{2}

Si

_{2}

O

_{7}

crystals form the C-type rare-earth pyrosilicate structure with space group

C 2 / m

and are colorless and transparent or milky white, whereas the Er-variant is D-type,

P 2_{1} / b

, and has a pink hue originating from Er

^{3 +}

. The crystal structures of the grown single crystals were confirmed through a Rietveld analysis of the powder X-ray diffraction patterns from pulverized crystals. The specific heat of both C-Yb

_{2}

Si

_{2}

O

_{7}

and D-Er

_{2}

Si

_{2}

O

_{7}

measured down to 50 mK indicated a phase transition at

T_{N} \approx

1.8 K for D-Er

_{2}

Si

_{2}

O

_{7}

and a broad Schottky-type feature with a sharp anomaly at 250 mK in an applied magnetic field of 0.8T along the c-axis in the case of C-Yb

_{2}

Si

_{2}

O

_{7}

. Full article

(This article belongs to the Special Issue Optical Floating Zone and Crystals Grown by this Method)

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16 pages, 4684 KiB

Open AccessArticle

2-Chloroalkoxy-Substituted Pentafluorinated Bistolanes as Novel Light-Emitting Liquid Crystals

by Shigeyuki Yamada, Kazuya Miyano, Tomohiro Agou, Toshio Kubota and Tsutomu Konno

Crystals 2019, 9(4), 195; https://doi.org/10.3390/cryst9040195 - 6 Apr 2019

Cited by 10 | Viewed by 3802

Abstract

In this study, we designed and synthesized novel pentafluorinated bistolane derivatives with 2-chloropentyl or 2-chlorohexyl flexible units as novel light-emitting liquid crystals (LELCs). By measuring the phase-transition behaviors, all derivatives were found to display liquid-crystalline (LC) phases during both heating and cooling processes. [...] Read more.

In this study, we designed and synthesized novel pentafluorinated bistolane derivatives with 2-chloropentyl or 2-chlorohexyl flexible units as novel light-emitting liquid crystals (LELCs). By measuring the phase-transition behaviors, all derivatives were found to display liquid-crystalline (LC) phases during both heating and cooling processes. Among the novel bistolanes, the S- and R-configured derivatives exhibited a chiral nematic (N*) phase with a typical Grandjean optical texture. Interestingly, the chiral derivatives also exhibited a blue phase with a typical platelet texture in a narrow temperature range (2–4 °C). Photophysical measurements revealed that the 2-chloroalkoxy-substituted pentafluorinated bistolanes exhibited intense photoluminescence (PL) both in solution and in crystalline phases. The PL characteristics, especially the maximum PL wavelength, were found to switch sensitively during the heating and cooling cycles depending on the molecular aggregates through the crystal (Cr) ⇄ N* phase transition. The 2-chloroalkoxy flexible units induced dynamic changes in the LC and PL properties, providing valuable insight into the potential of various LELCs as PL sensing materials. Full article

(This article belongs to the Special Issue Synthesis and Properties of Light-emitting Liquid Crystals)

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Crystals, Volume 9, Issue 4 (April 2019) – 44 articles

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