Pure Single Crystals Research Articles

Application of Computer-Aided Precious Metal Materials in Electrochemistry of Ceramic Jewelry Design

In order to solve the electrochemical application of precious metal materials in ceramic jewelry design, a computer-aided design method of precious metal materials in ceramic jewelry was proposed. First, the potential energy surface analyzed in this paper is composed of the sum of disomy and trisomy, with different proportions of disomy and trisomy. Therefore, in the fitting process, the above two relations can be used to measure the contribution of the two-body term and the three-body term, respectively; secondly, from the viewpoint of lattice dynamics, precious metals are of special significance, because they are simple fcc lattice and large and pure single crystals can be obtained. Therefore, their accurate phonon dispersion curves can be obtained experimentally; finally, the phonon dispersion curves along the highly symmetric vector direction are given, and the calculated results are in good agreement with the experimental data. This shows that the new analytical potential energy surface accurately reproduces the interactions inside these crystals. The new analytical potential energy surfaces of the three noble metals correctly reproduce the macroscopic properties of the system, including elastic modulus, cohesive energy, and phonon dispersion curve, as well as important surface features. For all three systems, the order of the surface energies of the unreconstituted surfaces is (110) > (100) > (111), which is also correct. At the same time, the new potential energy surface gives the correct relaxation behavior of the unreconstituted surface.

Orientation Dependence on Bending Deformation Behavior of Pure Zinc Single Crystals

Three-point bending tests were performed on pure zinc single crystals with different crystal orientations to investigate orientation dependence on bending deformation behavior. With basal planes parallel to the neutral planes, the specimens deformed due to basal slips and formed a gull shape after deformation. On the other hand, specimens whose neutral planes are perpendicular to the basal planes and neutral axes are perpendicular to [0001] deformed due to second order pyramidal 〈c + a〉 slips, {1012} twinning and basal slips within {1012} twins, displaying a V shape. The bending deformation behavior of pure zinc single crystals was found to show strong orientation dependence. Also, the bending deformation behavior of pure zinc single crystals was found to differ from that of pure magnesium single crystals when the neutral plane and neutral axis are respectively perpendicular to the basal planes and [0001].

Growth and characterizations of pure and Cu-doped imidazolium L-tartrate (IMLT) single crystals: optical and NLO properties

Growth and characterizations of pure and Cu-doped imidazolium L-tartrate (IMLT) single crystals: optical and NLO properties

Predictive Crystal Plasticity Modeling of Single Crystal Nickel Based on First-Principles Calculations

To reduce reliance on experimental fitting data within the crystal plasticity finite element method (CPFEM), an approached is proposed that integrates first-principles calculations based on density functional theory (DFT) to predict the strain hardening behavior of pure Ni single crystals. Flow resistance was evaluated through the Peierls-Nabarro equation using the ideal shear strength and elastic properties calculated by DFT-based methods, with hardening behavior modeled by imposing strains on supercells in first-principles calculations. Considered alone, elastic interactions of pure edge dislocations capture hardening behavior for small strains on single slip systems. For larger strains, hardening is captured through a strain-weighted linear combination of edge and screw flow resistance components. The rate of combination is not predicted in the present framework, but agreement with experiments through large strains (~0.4) for multiple loading orientations demonstrates a possible route for more predictive crystal plasticity modeling through incorporation of analytical models of mesoscale physics.

Дифференциальная калориметрия монокристаллов ниобата лития

We conducted a series of calorimetric experiments with nominally pure lithium niobate single crystals of congruent composition from different manufacturers and with different cuts, the samples were exposed to temperatures of up to 1100 ℃. For all samples, a temperature feature is observed in the range of 800–900 °C, regardless of their crystallographic orientation. The calculated activation energy of about 150 kJ/mol indicates the diffusion mechanism of the transformation, most likely associated with the high mobility of lithium and niobium ions as well as the possibility of formation of oxygen vacancies in the crystal lattice of lithium niobate. In some cases, this technique can serve as a technological parameter for the manufacture of lithium niobate crystals of optical quality.

Reveal the Humidity Effect on the Phase Pure CsPbBr3 Single Crystals Formation at Room Temperature and Its Application for Ultrahigh Sensitive X‐Ray Detector (Adv. Sci. 2/2022)

CsPbBr3 perovskite single crystals High quality phase pure CsPbBr3 perovskite single crystals are grown by solvent evaporation method under controlled humidity conditions. Meanwhile, the humidity is revealed as a key factor affecting the phase transformation of CsPbBr3 at room temperature. Moreover, the prepared CsPbBr3 single crystals are applied for the long-term working high performance X-ray detectors. More details can be found in article number 2103482 by Jingjing Chang and co-workers.

Computational, Spectral and Structural Studies of New Hydrazinium Hydrogen Phthalate Monohydrate Salt

Pure single crystals of Lewis acid-base salt, hydrazinium hydrogen phthalate monohydrate (HHPMH) has been synthesized, crystallized and isolated as a single crystal by slow evaporation method at room temperature (22 ºC). Analysis of analytical, spectral, thermal and structural data confirmed the salt formation in aqueous medium. The analytical data is in favour of the proposed composition HOOC-C6H4COO N2H5·H2O. The compound crystallized in a monoclinic crystal system and P21/C space group with cell parameters, a = 15.409(3) Å, b = 10.292(2) Å and c = 6.7087(12) Å. Though strong intramolecular hydrogen bonding interaction is anticipated between acidic hydrogen of HHPMH and deprotonated carboxylate oxygen surprisingly in the present case it is absent and a weak interaction is observed between acidic hydrogen and water molecule, which is quite evident from the ORTEP diagram. The nature of interactions between hydrazine cation and hydrogen phthalate ion and the crystal packing diagram from various types of intermolecular contacts were determined by Hirshfeld surface analysis. The compound was stable up to 40 ºC and undergoes dehydration from 40-70 ºC with an endotherm at 47 ºC. The experimental and theoretical infrared spectra are also in favour of the formation of ionic crystal. The molecular structure was optimized using B3LYP method by 6-311G (d,p) basis set. The energy gap between HOMO and LUMO is 7.7340 eV. Theoretical calculation based on DFT studies and natural bond orbital analyses has been carried out to evaluate the molecular electrostatic potential. The structure was optimized by DFT and the vibrational frequencies were calculated. Comparison of experimental and optimized structures revealed that there is a good coincidence between the two.

Unusual domain growth during local switching in triglycine sulfate crystals

Formation and growth of isolated lenticular domains created by local switching using a biased tip of the scanning probe microscope in nominally pure triglycine sulfate single crystals have been studied experimentally. The obtained unusual change in the domain shape during growth has been considered in terms of a kinetic approach and attributed to simultaneous stochastic step generation for domain widening and deterministic nucleation (step generation at the domain vertices) for domain elongation. The main parameters of the domain wall motion have been extracted by fitting of the field dependence of the domain length and width. The obtained results provide a useful insight into the features of the domain structure kinetics in the uniaxial ferroelectrics and can be used for development of the domain engineering methods.

A critical field study of ferroelectric domain in Al-doped KNbO3 single crystal

-Ferroelectric domain engineering is important for studying the dipolar structure of these materials. This dipolar structure is formed because of defects and imperfections produced using various doping. The KNbO3 ferroelectric single crystal was prepared using flux methods. Al2O3 aluminum trioxide (Al) was used as a dopant in a KNbO3 crystal. The domain structure of the crystal was studied by applying electric fields of 50 V/cm, 60 V/cm, 70 V/cm, 80V/cm, and 100 V/cm in an Al-doped KNbO3 single crystal. Furthermore, the critical field on which domains were nucleated after applying the electric field, was also studied. This work confirmed that the critical field of nucleation of the new domain in an Al-doped KNbO3 single crystal was 70 V/cm, which is slightly less than that of pure KNbO3 single crystal.

Effect of crystal orientation on fatigue crack initiation life in pure aluminum single crystals

The crystal orientation dependence of fatigue crack initiation life was studied on 99.99 % pure aluminum single crystals. The fatigue crack initiation life is not ruled only by Primary slip system, but also affected by the second, the third and the fourth slip systems. Fatigue damage formation is accelerated in the crystal orientation which has equally large Schmid factor both on Primary and Critical slip planes, but it is restrained as Schmid factor on Conjugate slip plane increases. X-ray micro-beam back reflection Laue observation showed that the subgrain structure was remarkably developed. The configuration of crystallographic fatigue damage depends on the crystal orientation. The secondary slip system plays an important role in it. The total misorientation observed at the fatigue crack initiation takes about 5.5 × 10-2 rad, not depending on the crystal orientation and the shear stress amplitude. This suggests that the fatigue crack is initiated when the dislocation density at the subgrain boundary reaches a certain value.

Pulsed vs dc I-V measurements on AlxV1-xO2 (x = 0–0.013) single crystals: Unmasking a non-thermal electric field effect on these crystals

The thermally induced insulator–insulator transition in Al-doped and the insulator–metal transition in doped as well as in pure VO2 single crystals are replicated in their dc I-V characteristics due to self-heating. In the investigation reported herein, self-heating (a lattice effect) was totally or almost totally avoided by using current pulses of millisecond durations, thus leaving the stage for electron heating. At low currents, the pulsed I-V are close to, or perfectly Ohmic, corresponding to the room temperature value of the resistance. Above a threshold, the voltage jumped backward and the current upward, marking a finite drop in resistance by 12%–24% for the different crystals; from there on, the resistance decreased linearly with the increasing voltage. Most R(V) traces were reproducible with small hysteresis upon increasing and decreasing currents. This behavior suggests an insulator-mixed-metal-insulator transition with metallic domains increasing with the increasing voltage (current). No reproducible behavior of the pulsed I-V characteristic of Al-doped crystals suggests onset of a non-thermal insulator–insulator transition. The interesting question now is what is the true nature of the material under the high pulsed voltage.

Reveal the Humidity Effect on the Phase Pure CsPbBr3 Single Crystals Formation at Room Temperature and Its Application for Ultrahigh Sensitive X-Ray Detector.

Generally, growing phase pure CsPbBr3 single crystals is challenging, and CsPb2Br5 or Cs4PbBr6 by‐products are usually formed due to the different solubilities of CsBr and PbBr2 in the single solvent. Herein, the growth of high‐quality phase pure CsPbBr3 perovskite single crystals at room temperature by a humidity controlled solvent evaporation method is reported first. Meanwhile, the room temperature phase transition process from three dimensional (3D) cubic CsPbBr3 to two dimensional (2D) layered tetragonal CsPb2Br5 and the detailed mechanism induced by humidity are revealed. Moreover, compared with the organic–inorganic perovskite, the prepared CsPbBr3 single crystals are much more stable under high humidity, which satisfies the long‐term working conditions of X‐ray detectors. The X‐ray detectors based on CsPbBr3 single crystals show a high sensitivity and a low detection limit of 1.89 μGyair s–1, all of which meet the needs of medical diagnosis.

Electrical Properties of Pure and Modified Copper Tartrate Single Crystals

The present paper reports the electrical properties of pure and sodium modified copper tartrate single crystals. Single crystal growth of these materials followed by their characteristics has already been published somewhere else. Having achieved the growth of pure and sodium modified copper tartrate single crystals and established their basic characteristics, it is thought worthwhile to have an understanding of their electrical properties and their modification on replacement of some copper ions in the lattice of copper tartrate by sodium ions. The electrical properties are studied by measuring electrical conductivity in the temperature range from 80 to 300 K. The study reveals that conductivity is a function temperature in these crystals. Moreover both pure and modified copper tatrate single crystal are semiconducting but the conductivity of pure modified copper tatrate single crystal is more than that of pure a copper tatrate single crystal. The results have been explained in terms variable range hopping model.

Investigations on structural, optical and electrical properties of holmium doped rubidium titanyl phosphate single crystals

The holmium doped rubidium titanyl phosphate single crystal was grown using a high-temperature flux method using rubidium polyphosphate as a flux compound. The structural nature of the grown Ho: RTP single crystal has been confirmed by powder XRD analysis. The addition of Ho dopant shows variations in the diffraction peaks refer to the combination of holmium with the RTP lattice. The UV absorption and transmittance study show no visible absorption induced by holmium. The electrical parameters like, dielectric constant, dielectric loss, AC conductivity and impedance have been studied up to the Curie point level of the material, and the results indicating that the doping of holmium reduces the electrical activities in the RTP single crystal, and there is no change in the Curie point of the Ho: RTP single crystal compared to pure RTP. The ferroelectric result shows that the polarization and coercive field of material have a lower value than the pure RTP single crystal due to the presence of holmium in the RTP, which is very useful for periodically poled device applications. Ferroelectric fatigue test on Ho: RTP shows that the grown crystal does not undergo polarization decay up to 5000 frequency cycles.

Forming laterally structured heterojunction with FAPbI3 film for improving performance of MAPbBr3 photodetectors

MAPbBr3 single crystal is coated with FAPbI3 film through the half-cladding method, which forms the laterally structured heterojunction. In comparison with pure MAPbBr3 single crystal, the optoelectronic properties of the heterojunction exhibit a rare dual narrowband detection characteristic located at excitonic absorption of respective MAPbBr3 and FAPbI3 due to the different penetration depth of light photodetection. In addition, as the applied bias voltage decreases, the charge collection efficiency at the shorter wavelength range also decreases. The self-power characteristics of the device can be attributed to the existence of the built-in electric field in the heterojunction, achieving a detectivity of 5.38 × 1012 Jones for red light at 0 V. And the fast response time without an external electric field is 6.6 × 10−2 s, which is much shorter than the reported MAPbI3/MAPbBr3 heterojunction photodetector. Our results pave the way for the simple synthesis of MAPbBr3/FAPbI3 heterojunction and their applications in photodiode and a high-performance photodetector with a fast response.

High-Pressure Polymorphs Nucleated and Stabilized by Rational Doping under Ambient Conditions.

High-pressure polymorphs can be obtained and stabilized at ambient pressure by utilizing dopants with more voluminous molecules, inducing internal strain in the structures. This effect has been confirmed for doped resorcinol and imidazole derivatives by nucleating and stabilizing their high-pressure phases under ambient conditions. The dopant molecular volume and concentration, as well as the bulk modulus of the polymorph in the binary system, are related to the stability region in the single-component phase diagram. High-pressure isothermal and isochoric recrystallizations yielded pure single crystals of resorcinol ε above 0.20 GPa and a new polymorph ζ above 0.70 GPa. These recrystallizations of pure resorcinol revealed within 1 GPa of the p–T phase diagram the boundaries and the stability regions of four resorcinol polymorphs α, β, ε, and ζ, contrary to the compression experiments on ambient-pressure polymorphs α and β, when the high-pressure phases were hidden behind the wide hysteresis extending to nearly 5 GPa. The hysteresis, originating from the H-bonding networks, hinders the formation of polymorphs ε and ζ when polymorphs α and β are compressed without melting or dissolving the crystals. Polymorph ζ is the only known resorcinol structure built of hydrogen-bonded layers.

Full-Stokes Polarimeter Based on Chiral Perovskites with Chirality and Large Optical Anisotropy.

Full-Stokes polarimeters, equipped with the capability of discriminating light polarization states, can find important applications in various optical and optoelectronic devices. Nevertheless, currently most full-Stokes polarimeters require complex and bulky optical elements or optical metasystems integrated with metasurfaces, which can increase the cost and cause energy loss. Here, the anisotropy of chiral 2D perovskite single crystals is explored and the full-Stokes polarimeter based on pure chiral 2D perovskite single crystals is reported. By using optical anisotropy and the ability to distinguish the helicity of the circularly polarized light, chiral 2D perovskite polarimeter integrates the polarizer, waveplate, and photodetector together and thus can be able to discriminate the polarization states of light. The as-fabricated device exhibits a photoresponsivity of 0.136 A W-1 and a detectivity of 1.2 × 1010 Jones. This study provides a paradigm to construct filterless on-chip Stokes polarimeter with great simplicity and low cost.

Rapid Synthesis of Bright, Shape‐Controlled, Large Single Crystals of Cs3Cu2X5 for Phase Pure Single (X = Br, Cl) and Mixed Halides (X = Br/Cl) as the Blue and Green Components for Printable White Light‐Emitting Devices

AbstractTernary copper halides have garnered significant interest for their bright, high quantum yield emission stemming from the radiative decay of self‐trapped excitons (STEs). Cesium copper halides have shown promise for use in optoelectronics, including light‐emitting devices (LEDs) for lighting and displays. To date several synthetic procedures for Cs3Cu2X5 (X = Cl, Br, and mixed Br/Cl) have been proposed for making nanocrystals, microcrystals, or polycrystalline thin films. Here, a synthetic method for making large single crystals (SCs) with millimeter dimensions in less than 30 min is presented. Phase pure mixed halide SCs are also produced and in‐depth structural analysis has been performed for the first time, definitively showing the site preferences for mixing chloride into the pure Cs3Cu2Br5 structure. Quantum yields for SCs of X = Cl and Br are 100% and 27% respectively, with long lifetimes and strong evidence of STE emission. This synthesis can be used to produce white light UV‐downconversion LEDs using ternary copper halides as the blue and green components along with the commercial red phosphor K2SiF6:Mn4+. These devices give a Commission Internationale de l'Éclairage (CIE) coordinate of (0.3327, 0.3342) and color rendering index of 90% at a color temperature of ≈5500 K.

Electronic States and Energy Dissipations of Vortex Core in Pure FeSe Single Crystals Investigated by Microwave Surface Impedance Measurements

In order to clarify electronic states and energy dissipations due to a motion of a vortex core in pure FeSe, which is a candidate superconductor possessing a super-clean core, we measured the microwave surface impedance of pure FeSe single crystals under finite magnetic fields. From the magnetic-field dependence of the flux-flow resistivity, we found that a barometer of electronic states inside the vortex core $\omega_{0}\tau_{\rm core}$ is $1\pm0.5$, suggesting that the vortex core of pure FeSe is in the moderately clean regime contrary to the expectation of the super-clean core. We also found that the mean-free path inside the vortex core is suppressed at the distance of the order of the core radius. Based on observed results and previous reports, we discussed possible origins of rather small $\omega_{0}\tau_{\rm core}$ value in terms of the multiple-bands nature of FeSe and additional mechanisms producing extra energy dissipations specific to the vortex core in motion.

Doped Emitting Cesium Silver Halides as X‐Ray Scintillator with Fast Response Time, High Absorption Coefficient, and Light Yield

Radioluminescence materials (scintillators) are widely investigated because of their potential application in many fields, such as medical imaging, security‐related techniques, and nondestructive inspection. However, the fabrication of scintillator materials with simultaneously fast response time, high absorption coefficient, and high light yield, as well as low toxicity is still a challenge. Herein, the synthesis of Cu(I)‐doped Cs2AgI3 single crystals (SCs) with a 1D crystal structure is presented. A bright blue‐green photoluminescence (PL) is observed after incorporating Cu+ into the Cs2AgI3 SCs under UV irradiation at room temperature. The PL quantum yield of the doped samples can reach up to 73% at a Cu+ concentration of 0.66%. Experimental and theoretical studies show that the blue‐green emission may originate from self‐trapped excitons, which is further verified by photophysical results from control experiments on pure Cs2AgI3 SCs. Upon X‐ray excitation, Cu‐doped SCs exhibit fast scintillation decay time (288 ns), high light yield (27 000 photons per MeV), and high absorption coefficient compared with the commercial product (CsI: Tl). These results suggest that Cu‐doped Cs2AgI3 is an ideal scintillator, which will be a promising candidate for potential application in dynamic real‐time imaging and radiation detection.