Properties Of Crystals Research Articles

Improvement in Crystallization, Thermal, and Mechanical Properties of Flexible Poly(L-lactide)-b-poly(ethylene glycol)-b-poly(L-lactide) Bioplastic with Zinc Phenylphosphate.

Poly(L-lactide)-b-poly(ethylene glycol)-b-poly(L-lactide) (PLLA-PEG-PLLA) shows promise for use in bioplastic applications due to its greater flexibility over PLLA. However, further research is needed to improve PLLA-PEG-PLLA's properties with appropriate fillers. This study employed zinc phenylphosphate (PPZn) as a multi-functional filler for PLLA-PEG-PLLA. The effects of PPZn addition on PLLA-PEG-PLLA characteristics, such as crystallization and thermal and mechanical properties, were investigated. There was good phase compatibility between the PPZn and PLLA-PEG-PLLA. The addition of PPZn improved PLLA-PEG-PLLA's crystallization properties, as evidenced by the disappearance of the cold crystallization temperature, an increase in the crystallinity, an increase in the crystallization temperature, and a decrease in the crystallization half-time. The PLLA-PEG-PLLA's thermal stability and heat resistance were enhanced by the addition of PPZn. The PPZn addition also enhanced the mechanical properties of the PLLA-PEG-PLLA, as demonstrated by the rise in ultimate tensile stress and Young's modulus. We can conclude that the PPZn has potential for use as a multi-functional filler for the PLLA-PEG-PLLA composite due to its nucleating-enhancing, thermal-stabilizing, and reinforcing ability.

First-principles prediction on the structural stability, electronic, optical and mechanical properties of TiBC, Ti6Si2B and Ti6Ge2B

The crystal structure stability, mechanical, optical and thermodynamic properties of TiBC, Ti6Si2B and Ti6Ge2B were predicted using the first principles calculations. The analysis of phonon dispersion curves, formation enthalpies, energy bands, and density of states demonstrate that TiBC, Ti6Si2B and Ti6Ge2B exhibit structure stability and metallic properties. The tensile strength of TiBC, Ti6Si2B and Ti6Ge2B were simulated, the results showed that the tensile strength of TiBC was the best. Anisotropy was explored by anisotropy index, 3D surface constructions and 2D projections. The order of anisotropy is TiBC > Ti6Ge2B > Ti6Si2B. The optical properties showed that TiBC, Ti6Si2B and Ti6Ge2B have strong long-wave absorption capacity. Finally, Debye temperature and sound velocity were investigated, the order of Debye temperature is: TiBC > Ti6Si2B > Ti6Ge2B.

Crystallization behavior and properties of ZnO–MgO–Al2O3–SiO2 transparent glass-ceramics with SnO2 and ZrO2 as nucleating agents

Transparent ZnO–MgO–Al2O3–SiO2 (ZMAS) glass-ceramics comprising ZrO2 and SnO2 as nucleating agents were prepared via melting and two-step heat treatment. The effects of varying the SnO2 concentration (1–3 mol%) on the crystallization behavior, microstructures, and mechanical properties of the glass-ceramics were investigated. Increasing the SnO2 content promoted the precipitation of spinel and gahnite because SnO2 improved the formation of ZrO2 nanocrystals, which provided nucleation sites for subsequent crystallization. When the SnO2 content was varied between 2 and 3 mol%, the crystallization behavior of the ZMAS glass-ceramics showed little difference, and SnO2 crystals precipitated from the glass at a relatively low crystallization temperature. In addition, glass-ceramics containing 2 and 3 mol% SnO2 exhibited average grain sizes of ∼26 and ∼29 nm, respectively, but their transmittance decreased to ∼52% and ∼50%, respectively, owing to grain aggregation. The best overall performance was achieved when the SnO2 content of the glass-ceramic was 3 mol% and heat treatment was conducted at 780 °C for 3 h and 960 °C for 2 h, with the resulting glass-ceramic exhibiting a bending strength of ∼187 MPa and a Vickers hardness of ∼845 kgf/mm2.

Moderation of [Bi3+/Na1+] molar ratio for enhancement of dielectric and energy storage properties of NaNbO3 ceramics

Lead-free (Na1−3xBix)(Nb0.75Ti0.25)O3 (x = 0.0, 0.05, 0.1, 0.125 and 0.15) (NN-BT) ceramics were synthesized using solid-state reaction technique. The effect of Bi3+ into the crystal structure, dielectric, ferroelectric and energy storage properties of NNT ceramics were investigated. Pure NNT shows present perovskite structure with orthorhombic crystal structure at x ≤ 0.125, while Na3NbO8-NaNbO3 composite phase has been detected at x = 0.15. The tolerance factor (τ) decreased from 0.97 (x = 0.0) to 0.82 (0.15) which signified the composition deviated from perovskite structure at 0.15. Significant enhancement of dielectric constant at room temperature has been achieved by increasing Bi-content and the maximum value (∼1500) obtained at 0.1. The largest value of maximum polarization (Pmax) and smallest value of remnant polarization (Pr) were achieved at x = 0.1 due to orthorhombic NaNbO3 and rhombohedral (Na0.5Bi0.5)TiO3 coexistence phases. The substitution of monovalent (Na1+) by trivalent (Bi3+) lead to create sodium vacancies into the A-sites of NNT lattice subsequently increased the cations disorder and charge misfit. The maximum recoverable energy storage density (Wrec = 17.5 J cm−3) and energy storage efficiency (η = 80%) were achieved at x = 0.1, E ∼ 700 kV cm−1. Partially, (NNTB0.1) exhibit an outstanding stability of energy storage properties in terms of temperature range (25 to 150 °C) and frequency stability (2–20Hz). The present results imply the moderation ratio of Bi/Na plays an important role for enhancement of energy storage properties of NaNbO3 anti-ferroelectric ceramics.

Targeting urinary calcium oxalate crystallization with inulin-type AOFOS from Aspidopterys obcordata Hemsl. for the management of rat urolithiasis

Ethnopharmacological relevance:Calcium oxalate crystals play a key role in the development and recurrence of kidney stones (also known as urolithiasis); thus, inhibiting the formation of these crystals is a central focus of urolithiasis prevention and treatment. Previously, we reported the noteworthy in vitro inhibitory effects of Aspidopterys obcordata fructo oligosaccharide (AOFOS), an active polysaccharide of the traditional Dai medicine Aspidopterys obcordata Hemsl. (commonly known as Hei Gai Guan), on the growth of calcium oxalate crystals. Aim of the study:To investigated the effectiveness and mechanism of AOFOS in treating kidney stones. Materials and methods:A kidney stones rats model was developed, followed by examining AOFOS transport dynamics and effectiveness in live rats. Additionally, a correlation between the polysaccharide and calcium oxalate crystals was studied by combining crystallization experiments with density functional theory calculations. Results:The results showed that the polysaccharide was transported to the urinary system. Furthermore, their accumulation was inhibited by controlling their crystallization and modulating calcium ion and oxalate properties in the urine. Consequently, this approach helped effectively prevent kidney stone formation in the rats. Conclusions:The present study emphasized the role of the polysaccharide AOFOS in modulating crystal properties and controlling crystal growth, providing valuable insights into their potential therapeutic use in managing kidney stone formation.

Dual-channel phonon transport leads to low thermal conductivity in pyrochlore La2Hf2O7

The pyrochlore oxide La2Hf2O7 (LHO) has attracted extensive attention in thermal management applications. Accurate determination and comprehensive understanding of thermal conductivity (κ) stand as imperative prerequisites for the effective utilization and manipulation of LHO in various applications. In this study, with the assistance of machine learning interatomic potential, we investigate the microscopic mechanisms of phonon thermal transport in LHO crystals. Our findings show that the thermal transport in LHO defies a precise explication through the conventional framework of the Boltzmann transport equation (BTE) due to the emergence of diffusive phonon modes, engendered by strong anharmonicity. Using the state-of-the-art dual-phonon model incorporating both propagating and diffusive modes, we successfully reproduce the experimentally measured results in both magnitude and temperature dependence. It is also shown that the thermal conduction in LHO crystals is dominated by the propagating modes at low temperatures while by the diffusive modes at high temperatures, which synergistically lead to a low κ for LHO crystals. The novel insights into phonon thermal transport provide a stepping stone for regulating the thermal transport properties of LHO crystals.

Mechanisms of Hysteresis and Reversibility across the Voltage-Driven Perovskite-Brownmillerite Transformation in Electrolyte-Gated Ultrathin La0.5Sr0.5CoO3-δ.

Perovskite cobaltites have emerged as archetypes for electrochemical control of materials properties in electrolyte-gate devices. Voltage-driven redox cycling can be performed between fully oxygenated perovskite and oxygen-vacancy-ordered brownmillerite phases, enabling exceptional modulation of the crystal structure, electronic transport, thermal transport, magnetism, and optical properties. The vast majority of studies, however, have focused heavily on the perovskite and brownmillerite end points. In contrast, here we focus on hysteresis and reversibility across the entire perovskite ↔ brownmillerite topotactic transformation, combining gate-voltage hysteresis loops, minor hysteresis loops, quantitative operando synchrotron X-ray diffraction, and temperature-dependent (magneto)transport, on ion-gel-gated ultrathin (10-unit-cell) epitaxial La0.5Sr0.5CoO3-δ films. Gate-voltage hysteresis loops combined with operando diffraction reveal a wealth of new mechanistic findings, including asymmetric redox kinetics due to differing oxygen diffusivities in the two phases, nonmonotonic transformation rates due to the first-order nature of the transformation, and limits on reversibility due to first-cycle structural degradation. Minor loops additionally enable the first rational design of an optimal gate-voltage cycle. Combining this knowledge, we demonstrate state-of-the-art nonvolatile cycling of electronic and magnetic properties, encompassing >105 transport ON/OFF ratios at room temperature, and reversible metal-insulator-metal and ferromagnet-nonferromagnet-ferromagnet cycling, all at 10-unit-cell thickness with high room-temperature stability. This paves the way for future work to establish the ultimate cycling frequency and endurance of such devices.

Varifocal occlusion in an optical see-through near-eye display with a single phase-only liquid crystal on silicon

We propose a near-eye display optics system that supports three-dimensional mutual occlusion. By exploiting the polarization-control properties of a phase-only liquid crystal on silicon (LCoS), we achieve real see-through scene masking as well as virtual digital scene imaging using a single LCoS. Dynamic depth control of the real scene mask and virtual digital image is also achieved by using a focus tunable lens (FTL) pair of opposite curvatures. The proposed configuration using a single LCoS and opposite curvature FTL pair enables the self-alignment of the mask and image at an arbitrary depth without distorting the see-through view of the real scene. We verified the feasibility of the proposed optics using two optical benchtop setups: one with two off-the-shelf FTLs for continuous depth control, and the other with a single Pancharatnam–Berry phase-type FTL for the improved form factor.

Study of the Structural and Switching Properties of Ga2Te5 Crystals

The structural parameters of Ga2Te5 crystals grown using the Bridgman method have been studied. X-ray diffaction analysis revealed the crystal structure of Ga2Te5 in the tetragonal phase. In addition, crystalline size, strain, and dislocation density were calculated with the Sherrer model and the Williamson-Hall (W-H) model. The switching effect was achieved for Ga2Te5 crystals. Furthermore, the effect of temperature and light intensity was studied for Ga2Te5 crystals. The results show that temperature and light intensity affect switching characteristics such as threshold current (ith), threshold voltage (Vth), threshold power (Pth), and resistance ratios from a high-resistance OFF state to a low-resistance ON state (ROFF/RON).

Deformation behavior and magnetic properties of equiatomic FeNi single crystals

An equiatomic Fe–Ni alloy in its disordered A1 structure is a soft magnetic alloy. On ordering to the L10 ordered phase, it shows significant magneto-crystalline anisotropy and a strong permanent magnet behavior and is of interest as a rare earth-free permanent magnet. However, synthesis of an L10 phase in a bulk form remains a challenge due to its low critical ordering temperature Tc and consequent extremely slow ordering kinetics. This phase is present in asteroids, and how it was formed remains unclear. The likely mechanism is enhanced diffusion kinetics due to extreme dislocation densities and vacancy concentrations produced by deformation during asteroid collisions and the presence of S. Prior to examining extreme deformation in an FeNi alloy comparable to that in asteroid collisions, low strain rate deformation behavior, magnetic properties, and the structure of undoped and S-doped [100]-oriented FeNi single crystals were carried out. Controlled deformation at a strain rate of 1 × 10−5/s showed the yield point to be 89 MPa, and the critical resolved shear stress was 25.7 MPa. The dislocation densities obtained were ∼1017/m2. The saturation magnetization value was ∼147–151 emu/g both before and after deformation, comparable to NdFeB magnets. Coercivity increased slightly from ∼0.04–0.4 to ∼5 Oe after deformation due to an increase in dislocation density. The x-ray diffraction scan of S-doped and deformed single crystals after annealing at 300 °C, just below Tc, showed no evidence of L10 order. These data serve as a baseline for extreme strain rate deformation where much higher dislocation densities and vacancy concentrations can be obtained to facilitate L10 order.

Theoretical and Experimental Study of the Electronic and Optical Properties of ZnIn2Se4 Crystals

Theoretical and Experimental Study of the Electronic and Optical Properties of ZnIn2Se4 Crystals

Electronic, Mechanical, and thermoelectric properties of Ge/Zn co-doped SnSe: first-principles calculations

Materials based on tin selenide have attracted significant attention due to their unique properties, particularly their high ZT value. This study investigates the impact of co-doping Germanium and Zinc on the electronic, mechanical, and thermoelectric properties of SnSe crystal using first-principles calculations. The doped structure demonstrated a p-type semiconducting behavior with a triclinic stable structure, which was predicted by the calculated elastic constants. Thermoelectric properties were studied for both doped and undoped systems across a wide range of carrier concentrations and temperatures. Results showed that co-doping SnSe with Ge/Zn reduced electronic thermal conductivity at room temperature while simultaneously doubling the Seebeck coefficient. This promising combination of features suggests high thermoelectric performance for the material.

Fast and Facile Synthesis of Passivated Perovskite Single Crystals with Zn-Porphyrin Derivatives

Organic-inorganic trihalide, ABX3 perovskite are excellent candidates for advanced optoelectronic applications beyond photovoltaics. Perovskite single crystals offer several advantageous special features, such as a long diffusion length, low trapped carrier density, and outstanding environmental stability to use in optoelectronics. In this work, Zn has been incorporated into MAPbBr3 single crystals as Zn- Porphyrin to passivate the bulk crystals and enhance their optical and electrical properties. The inverse temperature crystallization phenomenon was used to crystallize MAPbBr3 rapidly in hot solutions. The structural and optical characterization confirms that the passivation enhanced the optoelectronic properties of the single crystals.

First-principles and experimental study to investigate structural, elastic, electronic, thermal, and optical properties of KCdCl3 metal halide perovskite crystals

In this research, we examine the structural, elastic, anisotropic, acoustic, electronic, thermo-physical, and optical properties of KCdCl3 using both the density functional theory method as well as experimental data characterizations. The x-ray diffraction and Fourier transform infrared spectroscopy showed that our synthesized sample was well crystalline (orthorhombic), and the values of the lattice parameters are closely matched those of the first principles study. The scanning electron microscopy measurements of our sample morphology and microstructure showed a high grain size. The elastic property indicates that the structure is both mechanically and dynamically stable. The band structures and the density of state computation assured the semiconducting nature of our sample. Mulliken atomic populations showed ionic and covalent bonding in these materials, which can also be said to be mechanical property. The negative value of Cauchy’s pressure indicates the presence of angular bonding in the structure. In addition, the structure has high machinability. The phase transitions and thermal breakdown of KCdCl3 were examined by thermo-gravimetric analysis, and we found weight loss occurs in three stages. UV–visible spectrophotometers assessed the optical absorption and transmittance, which suggests that KCdCl3 is a strong UV absorber that gradually rises with wavelength. While the elastic and mechanical characteristics are anisotropic, the optical parameters are almost isotropic. The high UV reflectivity (∼28.5%) shows the material may not be an efficient radiation reflector but has great photovoltaic and optoelectronics potential.

Luminescence properties of CdF2 single crystals co-doped with Er3+ and Y3+ ions.

The luminescence properties of erbium and yttrium co-doped cadmium difluoride with three different concentrations of yttrium were investigated. First, we synthesized single crystal samples with good optical quality using the Bridgman technique. From the optical absorption spectra, recorded at room temperature, both in the ultraviolet-visible and infrared spectral ranges, Judd-Ofelt analysis was performed based on yttrium concentrations to predict the radiative properties of Er3+ luminescent ions. For the 10% optimum concentration of yttrium, a detailed photoluminescence investigation was carried out. We mainly explored green, red, and near-infrared fluorescence under different excitation wavelengths and presented their highlight spectroscopic characteristics. The desired transitions had relatively high emission cross-sections both under visible and near-infrared excitation. Optical gain followed a similar trend. Furthermore, the dynamic fluorescence study showed a significant increase in the measured lifetime under an 800 nm infrared excitation. The upconversion process under an 800 nm excitation produced quantum efficiency greater than 100% due to the contribution of more than one energy transfer mechanism.

Design, synthesis and Characterization of a novel antiferroelectric solid solution (1-x)PbHfO3-xBiAlO3

Antiferroelectric (AFE) materials are potentially useful for energy storage applications. Lead hafnate (PbHfO3) is one of the prototypical AFE materials. However, its critical field (Ecr) which is needed to induce the AFE to ferroelectric phase transition is close to the dielectric breakdown strength. To reduce Ecr, we prepare the solid solutions of (1-x)PbHfO3–xBiAlO3 (x = 0.00–0.04) via solid state synthesis. The crystal structures, dielectric behaviour, ferroelectric properties, and energy storage properties are investigated. A temperature-composition phase diagram is established. At room temperature, the crystal symmetry of all compositions is orthorhombic with the Pbam space group. Upon heating, the transition to the AFE orthorhombic Imma phase is observed at the temperature TC1, which slightly decreases with increasing x, followed by the transition to the cubic phase at the temperature TC2, which does not depend on x. Distinct dielectric anomalies are observed at TC1 and TC2. It is found that BiAlO3 substitution reduces Ecr and the polarization–electric field relations display characteristic double hysteresis loops. For x = 0.04, at a comparatively small applied field of 130 kV/cm, the values of recoverable energy density (Wrec) and efficiency of 0.24 J/cm3 and 84 %, respectively, are obtained. At 190 °C, a Wrec = 0.75 J/cm3 and a very high efficiency of 92 % are obtained at the field of 50 kV/cm. Thus, the prepared material can potentially be used in high-temperature pulsed power capacitors for energy storage applications within the temperature range from room temperature up to 190 °C.

A new crystal form of Hx2TNBI·2H2O through solvent-induced crystallization

Polymorphism is universal in energetic materials (EMs), which is originated from the differences of molecular conformers and stacking mode. The polymorphic transition may lead to the change of crystal structure and properties of EMs. In this work, β-Hx2TNBI·2H2O (β-1) was successfully synthesized through solvent-induced conformational transition of Hx2TNBI·2H2O. From the perspective of quantum chemistry and molecular dynamics, the crystal stacking changes caused by different molecular conformations are discussed in detail, which leads to the properties difference of EMs. The results show that β-1 featured wave-like crystal stacking, making it less sensitive to external mechanical stimuli than α-Hx2TNBI·2H2O (α-1) (α-1: IS > 6 J, FS > 288 N; β-1: IS > 20 J, FS > 360 N). α-1 featured better the aromaticity, which gives it higher thermal stability than β-1 (α-1: Td = 186 °C; β-1: Td = 146 °C). Simultaneously, compared with β-1, α-1 has higher crystal density and detonation performance. This work provides a new and effective way to change the safety of EMs.

Investigation on the Correlation between Biaxial Stretching Process and Macroscopic Properties of BOPA6 Film.

Biaxially oriented polyamide 6 (BOPA6) films were prepared by extrusion casting and biaxial stretching with polyamide 6. The effects of different biaxially oriented on the macroscopic properties of BOPA6 were investigated by characterizing the rheological, crystallization, optical, barrier and mechanical properties. The results show that the increase of stretching temperature leads to the diffusion and regular stacking rate of BOPA6 chain segments towards crystal nuclei increases, the relative crystallinity increases, reaching 27.87% at 180 °C, and the mechanical strength and optical performance decrease. Heat-induced crystallization promotes the transformation of β-crystals to α-crystals in BOPA6, resulting in a more perfect crystalline structure and enhancing oxygen barrier properties. BOPA6 chains are oriented, and strain-induced crystallization (SIC) occurs during the biaxial stretching. Further increasing the stretch ratio, the relative crystallinity increased to 30.34%. The machine direction (MD) and transverse direction (TD) tensile strength of BOPA6 (B-33) are nearly two times higher than the unstretched film, reaching 134.33 MPa and 155.28 MPa, respectively. In addition, the permeation decreases to 57.61 cc·mil/(m2 day), and the oxygen barrier performance has improved by nearly 30% compared to the sample B-22. BOPA6 has a high storage modulus at a high stretching rate (300%/s). Rapid chain relaxation would promote the molecular chain disorientation, destroy the entangled network of the molecular chain, and lead to a decrease in tensile strength, reducing to about 110 MPa.

The Effect of Bi0.5Li0.5ZrO3-SrSnO3 Composite Doping on the Construction of Polymorphic Phase Boundaries and Enhanced Electrical Properties of K0.45Na0.55Nb0.965Sb0.035O3 Piezoelectric Ceramics

In this experiment, a new lead-free piezoelectric ceramics (1−x)K0.45Na0.55Nb0.965Sb0.035O3−x(0.9Bi0.5Li0.5ZrO3−0.1SrSnO3) were prepared by the conventional solid-phase method, and the effects of the doping amount of 0.9Bi0.5Li0.5ZrO3−0.1SrSnO3 on the K0.45Na0.55Nb0.965Sb0.035O3 ceramics on the crystal structure, microstructure, microscopic structure and electrical properties. All the doping ions entered the KNN lattice and formed a dense solid solution with a single-phase structure, and the phase structure of the ceramics coexisted from orthorhombic (O) to orthorhombic-tetragonal (O-T) phases in the range of 0 ≤ x ≤ 0.03, and transitioned to rhombohedral-tetragonal (R-T) phase coexistence when 0.035 ≤ x ≤ 0.05. The electrical properties of the ceramics were analyzed and the polymorphic phase boundary (PPB) region was obtained at x = 0.035 and had the best overall properties: d 33 = 324pC/N, k p = 49%, ε r = 1479, tanδ = 3.21%, P r = 31.98 μC/cm2, E c = 16.83 kV cm−1 and T C = 293°C. By The microstructural analysis of the ceramics showed that the appropriate amount of compound doping of the second element enhances the denseness of the ceramics as well as makes the grains uniformly distributed. These results indicate that the ceramics of this system have great prospects for future applications in the field of lead-free piezoelectric ceramics.

Crystal structure, morphology, and electrical properties of aluminum-doped LFP materials

AbstractThe effect of doping with aluminum compounds on the crystal structure, morphology, and electrochemical properties of LiFePO4 has been investigated with aluminum stearate, alumina, aluminum sulfate, and aluminum phosphate as dopants. The contraction of unit cell observed by XRD analysis and reduced lattice spacing determined by HRTEM of the doped crystals indicate that Al3+ ions, which occupy smaller space than lithium ions, are successfully doped into the lattice of LiFePO4. Lattice doping of aluminum ions enlarges Li+ transport channels; 1%-AlP-LFP has the slowest attenuation of discharge specific capacity. After 30 cycles of charge and discharge curve test at 0.5C, the retention rate of the sample is 97.43%. Owing to the substitution of S for O sites, and SO42− has a breaking effect on the carbon layer, this accelerates the capacity decay of 1%-AlS-LFP. The discharge capacity of 1%-AlS-LFP is 132.9 mAh/g, which is lower than 139.8mAh/g of LFP. The electrochemical impedance spectroscopy (EIS) results show that the resistance of 1%-AlP-LFP is 147.1 Ω, the resistance of LFP is 138.9Ω, and the resistance of LFP is 183.9Ω. The Li+ diffusion coefficient of 1%-AlP-LFP is partially increased; the double substitution of Al3+ and S2− slows the migration rate of Li+.