Homogeneous Crystals Research Articles

Investigation of the Structural Perfection of a LiNbO3:Gd3+(0.003):Mg2+(0.65 wt.%) Double-Doped Single Crystal Using the Raman Spectra Excited by Laser Lines in the Visible (532 nm) and Near-IR (785 nm) Regions

A compositionally homogeneous nonlinear optical single crystal of double-doped LiNbO3:Gd3+(0.003):Mg2+(0.65 wt.%) was obtained. Fine features of the LiNbO3:Gd3+(0.003):Mg2+(0.65 wt.%) crystal structure were studied from the Raman spectra of the first and second orders upon excitation by laser lines in the visible (532 nm) and near-IR (785 nm) regions. When the Raman spectrum was excited by a 785 nm laser line in the frequency range of 1000–2000 cm−1 for the first time, a number of low-intensity lines in the range of 900–2000 cm−1, corresponding to the second-order Raman spectrum, were discovered. The same lines also appear in the spectrum upon excitation by a laser line with a wavelength of 532 nm, but their intensities are significantly (by an order of magnitude or more) lower. It is shown that in the structure of the double-doped LiNbO3:Gd3+(0.003):Mg2+(0.65 wt.%), the crystal oxygen-octahedral clusters MeO6 (Me–Li, Nb, Gd, Mg) are slightly distorted, and in addition, the value R = [Li]/[Nb] ≈ 1 is close to that for a nominally pure stoichiometric crystal.

Evaluation of relative content and crystallization behavior of homogeneous crystals in poly (lactic acid) by terahertz spectroscopy

Poly (lactic acid) (PLA) is a typical polymer with homogeneous polymorphism. Its different crystal forms have their own crystallization paths, which endow it with special properties. Therefore, it is crucial to study the structure and crystallization behavior of PLA to better understand its properties. Here, we investigate PLA films obtained under different crystallization conditions by terahertz (THz) spectroscopy. The α′, α and their mixed crystal forms of PLA exhibit completely different spectral feature. Based on the frequency of THz characteristic peaks, we further determine the relative contents of α′ form and α form in PLA with mixed crystals, the validity of which is verified by comparing X-ray diffraction (XRD). Furthermore, the change of absorption intensity of different PLA films is significantly different with crystallization time, mainly manifested as the change rate of glassy PLA crystallized at 80 °C is faster than that of molten PLA. We believe that this is because the crystallization of the α form of PLA at 80 °C is at a disadvantage, which reduces the speed of conformational adjustment. The results show that THz spectroscopy can not only characterize the crystal changes of polymers, but can also be an effective method to study the kinetics of polymer crystallization.

Microstructure and phase evolution behavior of SiZrBC ceramic precursors synthesized via sol–gel method

ZrB2–SiC ceramics were successfully prepared via sol–gel method using phenyltrichlorosilane, borane dimethyl sulfide, and zirconium tetrachloride in stoichiometric amounts as the raw materials. The macromolecular network structure formed after the sol–gel process was investigated via Fourier transform infrared (FT–IR) spectroscopy. The phase evolution of the ZrB2–SiC ceramics were analyzed by FT–IR spectroscopy, X–ray diffraction, and transmission electron microscopy, whereas morphological and elemental analyses were performed using scanning electron microscopy. In particular, the change in phase composition was monitored after the pyrolysis from 1400 to 1500 ​°C, and the heat treatment of BZ6 precursor at 1500 ​°C enabled one to produce the ZrB2–SiC ceramic with a homogeneous crystal phase distribution. Therefore, the controllable microstructure adjustment of the ceramic phase composition could be achieved and a new way was paved for the structural and functional applications of ultra–high–temperature ceramics (UHTCs) series.

Magmatic-hydrothermal evolution of long-lived Nb-Ta-(Sn) mineralization in Lianyunshan, NE Hunan, South China

The Lianyunshan Complex (LYSC) is a Nb-Ta-Li-Be rare metals mining area in northeastern Hunan, South China. The deposit is composed of a granite-type rare-metal pegmatite mineralization that occurs as dikes around the LYSC. The present study examines the genetic relationship, fluid evolution, and metallogeny of the co-developed ore-free pegmatite (OFP) and ore-bearing pegmatite (OBP) in granite-related pegmatite-type Nb-Ta rare-metal deposits in the LYSC. Four minerals: columbite-tantalite (coltan), zircon, cassiterite, and monazite were investigated for their chemical and isotopic compositions. The coltan grains range from homogeneous crystals to zoned varieties with growth rims that result from equilibrium and disequilibrium reactions due to local changes in the physical and chemical conditions. These structures were altered by later metasomatic replacement processes related to the hydrothermal fluid activity and produced structures such as alteration rims, patches, irregular zonations, and complex zonations, with a corresponding increase in Ta. Coltan in OBP yielded two weighted mean 206Pb/238U ages of 135.9 ± 2.1 Ma and 120.5 ± 1.2 Ma, corresponding to magmatic (early-stage) and hydrothermal (late-stage) Nb-Ta mineralization ages, respectively. The cassiterite gives a weighted mean U-Pb mineralization age of 130.5 ± 3.9 Ma, which is interpreted as the magmatic-hydrothermal age (transitional stage). Zircon grains in OBP give a lower weighted mean U-Pb age of 121.5 ± 0.8 Ma, resulting from metamictization by the later fluid-assisted alteration and recrystallization in the late-stage hydrothermal event. Monazite grains from OFP yielded a weighted mean 206Pb/238U age of 137.1 ± 0.5 Ma, while zircon gives a mean U-Pb age of 130.3 ± 0.6 Ma. The ages of 137 and 130 Ma obtained for the OFP represent the magmatic (early-stage) and magmatic-hydrothermal stage (transitional) of OFP crystallization in the LYSC. Calculated zircon εHf (t) values and TDM2 ages from OFP (−7.6 to −5.4 and 1663−1532 Ma, respectively) and OBP (−8.7 to −8.2 and 1735−1704 Ma, respectively) are akin to those of the schist and metasandstone strata of the metasedimentary Lengjiaxi metasedimentary group—a melt source material to the LYSC composite batholith. We propose a long-lived ∼15 m.y. Nb-Ta-(Sn) mineralization model for the Lianyunshan complex.

Fast and Reproducible Matrix Deposition for MALDI Mass Spectrometry Imaging with Improved Glass Sublimation Setup

Sublimation is one of the preferred methods of choice for matrix deposition in high spatial resolution MALDI mass spectrometry imaging (MALDI-MSI) experiments. However, reproducibility and time are the major concerns for this setup. Here we present a lab-made glass sublimator with significant improvements in fine control of the vacuum with real-time monitoring and a rapid sublimation process of only 22 min. This method yielded reproducible homogeneous matrix crystals of <1 μm on the sample surface. MALDI-MSI was performed in tissue sections of barley inflorescence meristems at 15 μm spatial resolution, thus demonstrating its efficiency. Overall, we believe these simple yet effective new modifications can be easily adapted to the standard glass sublimation devices to achieve highly reproducible matrix deposition for high spatial resolution MALDI-MSI.

Flextegrity simple cubic lattices

Flextegrity lattices are spatial grids composed of stiff segments kept in contact by compliant pre-tensioned tendons. The kinematic skeleton is sensible to the orientation of the segments, since their relative rotation produces the straining of the tendons to an amount that depends upon the angle of rotation and the shape of the pitch surfaces of the contact joints: these dictate the constitutive properties of the lattice in response to external actions. Two- and three-dimensional lattices are investigated, in which the contact pitch surfaces, obtained with axial-symmetric toothed conjugate profiles, mimic the kinematics of spheres, centred at the nodes of a simple cubic lattice, in pure rolling motion. The allowed mechanisms are discussed under infinitesimal deformation, to recognize possible eigenstress states in the lattice. The response under finite deformations is worked out for two-dimensional lattices under symmetric and asymmetric loading. The theoretical predictions are compared with experimental results on 3D-printed physical models. Possible extensions are discussed for lattices with segments of varying size, different arrangements and multi-stable contact joints. The flextegrity microstructure can represent a mesoscopic model for homogeneous crystals composed of non-pointwise molecules, but it could actually be manufactured in metamaterials with peculiar properties.

Rational Design of Ferroelectric 2D Perovskite for Improving the Efficiency of Flexible Perovskite Solar Cells Over 23.

Despite the great progress of flexible perovskite solar cells (f-PSCs), it still faces several challenges during the homogeneous fabrication of high-quality perovskite thin films, and overcoming the insufficient exciton dissociation. To the ends, we rationally design the two-dimensional (2D) perovskite based on pyridine heterocyclic ring as the organic interlayer. Through regulating its dipole moment by attaching the ammounium cation on different positions of the pyridine ring, we succeed to realize the ferroelectricity of the 2D perovskite. We uncover that incorporation of the ferroelectric 2D material into 3D perovskite induces an increased built-in electric field (BEF), which enhances the exciton dissociation efficiency and suppresses the nonradiative recombination in the device. Moreover, the 2D seeds could assist the 3D crystallization process by forming more homogeneous and highly-oriented perovskite crystals, and releasing the tensile stress in the film. As a result, an impressive power conversion efficiency (PCE) over 23% has been achieved by the 2D/3D based f-PSCs with outstanding ambient stability. Moreover, the ferroelectric 2D perovskite shows piezoelectricity as well, which intrigues an upshifted band-bending at the ITO/perovskite interface and decreased hole transport barriers. The device thus presents higher PCE under tensile-stresses, which opens new possibilities for developing highly-efficient f-PSCs.

Blue photoluminescence enhancement achieved by zero-dimensional organic indium halidesviaa metal ion doping strategy

PLQE enhancement and emission manipulation have been achieved for zero-dimensional (MA)4InCl7through a metal ion doping strategy. Cs+or Mn2+doping result in defect passivation and homogeneous crystals, while Sb3+doping shift the emission center.

Large area inkjet-printed metal halide perovskite LEDs enabled by gas flow assisted drying and crystallization.

We demonstrate the upscaling of inkjet-printed metal halide perovskite light-emitting diodes. To achieve this, the drying process, critical for controlling the crystallization of the perovskite layer, was optimized with an airblade-like slit nozzle in a gas flow assisted vacuum drying step. This yields large, continuous perovskite layers in light-emitting diodes with an active area up to 1600 mm2.

Oligoaniline-assisted self-assembly of polyaniline crystals.

The conductivity and charge transport mobility of conjugated polymers (CPs) are largely correlated with their degree of crystallinity, rendering the crystallization of CPs an important endeavour. However, such tasks can be challenging, especially in the absence of sidechain functionalization. In this study, we demonstrate that the incorporation of a small amount of oligomers, specifically tetraaniline, can induce crystallization of the parent polymer, polyaniline, through a single-step self-assembly process. The resulting crystals are compositionally homogeneous because the oligomers and their parent polymer share the same repeating unit and are both electroactive. Mechanistic studies reveal that the tetraaniline forms a crystalline seed that subsequently guides the assembly of polyaniline due to their structural similarities. Applying this oligomer-assisted crystallization approach to polyaniline with defined molecular weights resulted in single crystalline nanowires for 5000 Da polyaniline, and nanowires with strong preferential chain orientation for those with molecular weights between 10 000 and 100 000 Da. Absorption studies reveal that the polymer chains are in an expanded conformation, which likely contributed to the high degree of packing order. Two-probe, single nanowire measurements show that the crystals have conductivity as high as 19.5 S cm-1. This method is simple, general, and can potentially be applied to other CPs.

Template-induced crystallization of charged colloids: a molecular dynamics study.

By using a large enough number of particles and implementing a parallel algorithm on the CUDA platform, we have performed brute-force molecular dynamics simulations to study the template-induced heterogeneous crystallization in charged colloids. Six kinds of templates, whose patterns include the planes of fcc(100), fcc(110), fcc(111), bcc(100), bcc(110) and bcc(111), have been implanted into the middle of the simulation box. Except the fcc(111) template, whose structure benefits not only fcc but also hcp crystals resulting in a similar behavior to homogeneous crystallization, bcc-type templates favor the formation of bcc crystals and bcc-like precursors while fcc-type templates favor the formation of fcc crystals and fcc-like precursors. Therefore, for fcc(100) and fcc(110) templates, heterogeneous crystallization will definitely result in a fcc crystallite. However, the results of heterogeneous crystallization that are induced by bcc-type templates are subtly different at different state points. At the state points where the interaction strength of charged colloids is weak and the fcc phase is thermodynamically stable, the bcc crystals formed with the promotion of bcc-type templates are not stable so as to tend to transform into fcc or hcp crystals. When the interaction strength of charged colloids is high, the predominant bcc crystals formed with the promotion of bcc-type templates can always persist within the time scale of simulation although not bcc but fcc crystals are thermodynamically stable.

Ion Addition by Electrolysis to Improve the Quantitative Analysis of Bacteria with MALDI-TOF MS

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is commonly applied to the identification of bacteria but rarely used for quantitative detection due to the inhomogeneous crystallization of the matrix leading to the unsatisfactory linear relationship between the sample amount and the mass spectrum signals. Herein, we proposed a noninterference ion addition (NIA) method by electrolysis to improve homogeneous crystallization during the evaporation progress of sample droplets on the target plates. The active metal wire was inserted in the droplet as the anode electrode, and metal ions were released through electrolysis. The directional migration of metal ions under the electric field can hinder the migration of matrix molecules to the boundary and homogenize the matrix crystals by forming spherical crystals. Simultaneously, trace cationic surfactant was added to the droplet for pinning the contact surface to define the circle crystallization region. The metal ions from the anode electrode wire were deposited on the surface of the target plates which served as the cathode. Therefore, ion addition has no interference effect on ionization during MALDI-MS detection. This NIA method benefits the homogeneous crystallization and so improves the quantitative analysis. NIA is suitable for biological samples with different matrices, and bacterial samples could be quantitatively analyzed.

STUDY OF THE HEAT OF DEHYDRATION OF D–FRUCTOSE SOLUTION

The heat of evaporation of water is the main component of the consumption during the drying of bio raw materials. Its share in the consumption depends not only on the initial moisture content of the drying object. As our previous studies have shown, the state of water in the material affects the total heat consumption. The state of water is determined by its chemical composition and structure. Drying objects rich in sugars deserve special attention. Sugars have a high tendency to hydration, are concentrated in the juice and determine both the kinetics and heat of dehydration. The most reliable data on glucose and fructose hydration are analyzed and presented. Measurement of the specific heat of evaporation of water r from fructose solutions with an initial concentration of 12.5 wt. % was performed in the evaporation calorimeter. Continuous registration of changes in heat flows and mass of the sample was ensured during the measurement process. The dependence of the reduced specific heat of evaporation of water (R = r/rtab) on the concentration of fructose was obtained in the isothermal mode at 40, 60 and 80 °C. The presented curves reflect the thermal processes occurring in the solution during water removal. The processes are characterized by an endothermic period of dehydration and an exothermic period of simultaneous dehydration and spontaneous homogeneous crystallization of fructose. It was found that the change in the degree of hydration of fructose in solution from 12.5 to 5 mol/mol occurs with increasing, almost linear, specific heat consumption. Removal of water from the first coordination sphere, when the degree of hydration decreases to values &lt;5, the increase in specific heat of evaporation is steeper and reaches the excess over the tabular values of heat of evaporation of pure water rtab by 6 – 7 %. The heat of spontaneous crystallization of fructose has a power greater than the power of endothermic heat consumption for dehydration, therefore, a general exothermic effect is recorded. It is shown that the measured specific heat of water evaporation increases with increasing concentration of solutions despite a decrease in the degree of hydration of fructose. It was established that water has a strong hydrogen bond with sugar in solutions in which the degree of hydration of fructose is less than ~5. Assumptions about strongly and weakly bound hydrated water in solutions of monosaccharides are substantiated.

Alignment‐inducement property of physicochemically reconstructed EVA layer via plasma ion‐beam treatment for liquid crystal system

Uniform and homogeneous liquid crystal (LC) alignment on a poly(ethylene‐co‐vinyl acetate) (EVA) layer subject to plasma ion‐beam (IB) treatment is confirmed. The layer molecular concentrations are controlled to 2, 4, and 6 wt%. Scanning electron microscopy exhibits a wrinkle pattern on the EVA surface that hinders LC alignment after IB treatment. However, X‐ray photoelectron spectroscopy shows chemical reconstruction on the surface; this induces strong van der Waals interactions with the LCs, which contribute to uniform LC alignment. The layer with higher molecular concentration is more heavily modified by IB treatment than that with low concentration, thereby achieving uniform LC alignment and overcoming topological disturbance. Contact angle analysis is used to verify that the surface energy increases via IB treatment; the uniform and homogeneous LC alignment is also confirmed by polarized optical microscopy and pretilt angle analysis. The EVA layer shows good optical transmittance and fine electro‐optical performances in terms of the switching and operating properties. Therefore, the plasma IB treatment is an effective method of deriving the surface characteristics of various polymeric materials for LC alignment, and the IB‐treated EVA layer has potential for application to LC systems.

Homogeneous nucleation of dislocations as a pattern formation phenomenon

Dislocation nucleation in homogeneous crystals begins as a symmetry-breaking elastic instability. In the absence of explicit nucleation centers, such instability develops simultaneously all over the crystal and due to the dominance of long range elastic interactions it advances into the nonlinear stage as a collective phenomenon through pattern formation. In this paper we use a novel mesoscopic tensorial model (MTM) of crystal plasticity to study the delicate role of crystallographic symmetry in the development of the dislocation nucleation patterns in defect free crystals. The model is formulated in 2D and we systematically compare the unfolding of the pattern formation phenomenon in lattices with square and triangular symmetry. To avoid the dominance of the conventional plastic mechanisms, we consider the loading paths represented by pure shears applied on the boundary of the otherwise unloaded body. These peculiar loading protocols can be qualified as exploiting the ‘softest’ and the ‘hardest’ directions and we show that the associated dislocation patterns are strikingly different.

Room-temperature polariton quantum fluids in halide perovskites

Quantum fluids exhibit quantum mechanical effects at the macroscopic level, which contrast strongly with classical fluids. Gain-dissipative solid-state exciton-polaritons systems are promising emulation platforms for complex quantum fluid studies at elevated temperatures. Recently, halide perovskite polariton systems have emerged as materials with distinctive advantages over other room-temperature systems for future studies of topological physics, non-Abelian gauge fields, and spin-orbit interactions. However, the demonstration of nonlinear quantum hydrodynamics, such as superfluidity and Čerenkov flow, which is a consequence of the renormalized elementary excitation spectrum, remains elusive in halide perovskites. Here, using homogenous halide perovskites single crystals, we report, in both one- and two-dimensional cases, the complete set of quantum fluid phase transitions from normal classical fluids to scatterless polariton superfluids and supersonic fluids—all at room temperature, clear consequences of the Landau criterion. Specifically, the supersonic Čerenkov wave pattern was observed at room temperature. The experimental results are also in quantitative agreement with theoretical predictions from the dissipative Gross-Pitaevskii equation. Our results set the stage for exploring the rich non-equilibrium quantum fluid many-body physics at room temperature and also pave the way for important polaritonic device applications.

Analytical and numerical modeling of optical second harmonic generation in anisotropic crystals using ♯SHAARP package

Electric-dipole optical second harmonic generation (SHG) is a second-order nonlinear process that is widely used as a sensitive probe to detect broken inversion symmetry and local polar order. Analytical modeling of the SHG polarimetry of a nonlinear optical material is essential to extract its point group symmetry and the absolute nonlinear susceptibilities. Current literature on SHG analysis involves numerous approximations and a wide range of (in)accuracies. We have developed an open-source package called the Second Harmonic Analysis of Anisotropic Rotational Polarimetry (♯SHAARP.si) which derives analytical and numerical solutions of reflection SHG polarimetry from a single interface (.si) for bulk homogeneous crystals with arbitrary symmetry group, arbitrary crystal orientation, complex and anisotropic linear dielectric tensor with frequency dispersion, a general SHG tensor and arbitrary light polarization. ♯SHAARP.si enables accurate modeling of polarimetry measurements in reflection geometry from highly absorbing crystals or wedge-shaped transparent crystals. The package is extendable to multiple interfaces.

The effects of Mn substitution on the crystalline phase structure, microstructure, DC resistivity, and magnetic-dielectric properties of Z-type hexaferrites

A series of the Ba1.5Sr1.5Co2-xMnxFe23O41 (x = 0.0–0.5) hexaferrites was prepared by the conventional solid-state reaction method. The crystalline phase structure, microstructure and magneto-dielectric properties of samples were investigated. Z-type and W-type phases were detected in hexaferrites sintered at 1200 °C. Mn substitution can reduce the content of the second phase, changes the ion occupancy, magnetic moment, and electron hopping in hexaferrite. Therefore, the magnetic, DC resistivity, and dielectric properties were altered, and the losses were successfully reduced in the substituted samples. Particularly, the Ba1.5Sr1.5Co1.8Mn0.2Fe23O41 hexaferrite has a more homogeneous crystal phase; its μi is 18.5, fr exceeds 1 GHz, and the Snoek’s constant reaches 18.55 GHz. At the same time, this hexaferrite were characterized by a relatively large magnetic quality factor and low dielectric losses (tanδε<0.05 below 500 MHz). This Z-type hexaferrite has excellent high-frequency magneto-dielectric properties and holds a potential for use in miniature antennas.

Nb-Ta oxides as recorders of hydrothermal activity in the Shihuiyao Rb-Nb-Ta-(Be-Li) deposit, Inner Mongolia, NE China

The Nb-Ta ore body in the Shihuiyao Rb-Nb-Ta-(Be-Li) deposit comprises muscovite-albite granite (MAG) and greisen (GR), with the dominant Nb-Ta minerals of columbite-group minerals (CGM) and ixiolite. The petrographic and chemical data suggest that the Nb-Ta oxides well record the magmatic-hydrothermal evolution process. The magmatic CGM are generally homogenous crystals or with oscillatory zoning patterns, while the CGM formed during the magmatic-hydrothermal transition stage overprints the early CGM crystals in the MAG or shows a normal zoning pattern (decreasing Nb/Ta ratios from the core to rim) in the GR, and possesses higher contents of Sc and Ti. The hydrothermal Nb-Ta oxides in both the MAG and GR share the same origin, i.e., the hydrothermal fluids exsolved from the magma at the late stage of magmatic evolution. However, distinct chemical differences between them indicate that a single fluid activity did not pervade the entire system; instead, two different hydrothermal processes were present: fluid metasomatism and water–rock reaction. The hydrothermal CGM generally occurs in the GR and metasomatizes the primary crystals by a coupled dissolution-reprecipitation mechanism. The chemical compositions of these CGM grains were significantly modified during this process, which was manifested by the increasing Sn and W contents in the reprecipitated phases. The ixiolite is most likely formed by another hydrothermal mechanism, i.e., water–rock reaction, during which the hydrothermal fluids can extract a large amount of Sn, Sc, U, and REE from the wall rocks or earlier formed magmatic phases and finally controlled the formation and chemical distribution of the ixiolite.

Application of low-solubility dolomite as seed material for phosphorus recovery from synthetic wastewater using fluidized-bed crystallization (FBC) technology

Fluidized-bed reactor technology was applied to recover phosphorus from solution via crystallization in a seeded (FBC, Fluidized-bed Crystallization) and unseeded (FBHC, Fluidized-bed Homogeneous Crystallization) system. Dolomite (CaMg(CO3)2) is applied as seed material to provide an existing surface in the seeded crystallization system. Under the optimum pH of 7.7, the presence of seed material in the FBC system enhanced the crystallization ratio of both phosphorus and calcium from 60% to 80%. The operating parameters, including - effluent pHe, up-flow velocity (U, m h−1), and cross-sectional loading (L, kg m−2 hr−1) were optimized in the FBC system. Under optimum conditions at pH 7.7, molar ratio of [Ca]0/[P]0=3.5/1, up-flow rate of 30 m h−1, and cross-sectional loading of 0.9 kg m−2 hr−1, the crystallization ratio (CR) and total removal (TR) of both phosphorus and calcium reached 85% and 92%, respectively. Based on the XRD and Raman pattern, it was confirmed the solid products consist of tricalcium phosphate (Ca3(PO4)2·xH2O) from both FBC and FBHC processes. An economic analysis shows that the disposal cost could be reduced from 0.92 US$ wastewater to 0.2 US$/m3. Phosphorus, encapsulated in a sparingly soluble crystalline form such as dolomite in the FBC system can be potentially used as a slow-release fertilizer and raw material for bio-ceramic and bioactive glass.