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Modification of perovskite-type oxides is an effective way to develop functional materials with advanced properties. The effects of cerium introduction into the A sublattice of La0.5Sr0.5FeO3−δ and variation of La:Sr ratio on the defect structure and charge transfer characteristics were studied in this work. The LaxSr0.85−xCe0.15FeO3−δ oxides were found to be single-phase with cubic (x = 0.1) and orthorhombic (x = 0.35, 0.5) structures. The oxygen content and electrical conductivity in the oxides were measured in a wide range of oxygen partial pressure at various temperatures. The oxygen content data were used for the defect equilibrium modeling. Good agreement with experimental data has been achieved in the model, assuming that a part of the cerium ions is not subjected to reduction. The fraction of such cerium ions decreases with increasing lanthanum content. The introduction of cerium has been found to result in a decrease in p-type conductivity and an increase in n-type and oxygen ion conductivity. The maximum ion conductivity, reaching 0.6 S·cm−1 at 950 °C, has been detected in the oxide La0.35Sr0.5Ce0.15FeO3−δ. The suitability of this oxide as an electrode material is uncertain, given that its thermal expansion coefficient exceeds that of the widely used solid electrolytes. However, the evaluation of oxygen permeability has shown that a 1-mm-thick membrane of this material under synthesis gas/air gradient can provide an oxygen flux density of up to 9 ml·cm−2·min−1 at 950 °C. Therefore, La0.35Sr0.5Ce0.15FeO3−δ can be recommended for testing in a membrane reactor for partial oxidation of methane. [ABSTRACT FROM AUTHOR]

Zn:Yb:Tm:LiNbO3 crystals with a range of [Li]/[Nb] ratios (0.94, 1.05, 1.20, and 1.38) were grown by Czochraski technique. The influence of [Li]/[Nb] ratio on the concentration of doped elements in grown crystal was investigated by inductively coupled plasma atomic emission spectrometry (ICP-AES). The defect structures formed at different [Li]/[Nb] ratios were studied by X-ray diffraction and INFRARED spectroscopy. The results show that, when the [Li]/[Nb] ratio increases, the segregation coefficients of Yb 3 + and Tm 3 + ions increase, while the segregation coefficient of Zn 2 + ions decreases. When the [Li]/[Nb] ratio in the melt increases to 1.20, the Zn:Yb:Tm:LiNbO3 crystal approaches the stoichiometric ratio. [ABSTRACT FROM AUTHOR]

[Display omitted] Hypothesis: In the interfacial wetting boundary, the superhydrophobic surface is often damaged, and the anisotropic wettability of its surface has attracted many researchers' attention. The "petal effect" surface has typical anisotropic wettability. We predict that under the dual conditions of structural defects and high impact velocity, the "petal effect" becomes more adhesive on the surface. Experiments: This study refers to the droplet state on rose petals, structural defects were constructed on the superhydrophobic surface. This paper studies the influence of macro-structural defects on the wettability change from natural to bionic "lotus effect" to "petal effect" in both static and dynamic angles. Findings: Macro defects significantly change the static contact angle of the superhydrophobic surface. The higher the impact velocity of the droplet, the higher the energy dissipation of the "petal effect" surface (DSHS), which improves the adhesion of the surface to the droplet and prolongs the contact time. It is found that the defect structure and high impact velocity will directly affect the deposition and desorption of droplets on the superhydrophobic surface, and they are both essential. This wetting dynamic law is very likely to be helpful in the quantitative design of defect structure scale for dynamic desorption of droplets on superhydrophobic surfaces. [ABSTRACT FROM AUTHOR]

Based on small angle neutron-scattering data from a nanocomposite composed of fullerene C60 (16.5 wt %) in an isotactic polypropylene matrix, we receive information on the clusterization of nanoparticles and define their geometric parameters and dimensionality. This study proposes an interpretation of the aggregation of particles with surface fractal properties in the size range up to 80 nm, as observed in a small-angle-neutron-scattering experiment. Based on well-known theories about the defect structure of the fullerene C60 molecule in non-Euclidean metrics, specifically disclinations and monopoles in the two-dimensional spherical space of Gödel type, we formulate a lattice version of the monopole gas model. Within this framework, we use the Monte Carlo method on a lattice with the Abelian projection to estimate the energies of monopole currents at various monopole concentrations. The proposed model enables the calculation of the fractal properties of C60 nanoparticles in a polymer composite, as well as the interpretation of the evolution of disclinations. [ABSTRACT FROM AUTHOR]

For the pursuit of high energy supercapacitors, the development of high performance pseudocapacitance or battery-type negative electrode material is urgently needed to make up for the capacity shortage of commercial electric double layer capacitor (EDLC) type materials. Herein, a porous and defect-rich FexBi2−xS3 solid solution structure is firstly constructed by employing Fe-doped Bi2O2CO3 porous nanosheets as a precursor, which presents dramatically increased energy storage performance than Bi2S3 and FeS2 phase. For the optimized FexBi2−xS3 solid solution (FeBiS-60%), the Fe solute is free and random dispersed in Bi2S3 framework, which can effectively modulate the electronic structure of Bi element and introduce rich-defect due to the existence of Fe(II). Meanwhile, the FeBiS-60%, constructed by pore nanosheets that are assembled by self-supported basic nanorod units, presents rich mesoporous channels for fast mass transfer and abundant active sites for promoting capacity performance. Therefore, a high capacitance of 832.8 F·g−1 at a current density of 1 A·g−1 is achieved by the FeBiS-60% electrode. Furthermore, a fabricated Ni3S2@Co3S4 (NCS)//FeBiS-60% hybrid supercapacitor device delivers an outstanding energy density of 85.33 Wh·kg−1 at the power density of 0.799 kW·kg−1, and ultra-long lifespan of remaining 86.7% initial capacitance after 8700 cycles. [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride) (PVDF) is predominantly characterized by alternating CH2 and CF2 units in a polymer backbone, originating from the head-to-tail addition of monomers or regular propagation. Due, to a small extent, to inverse monomer addition, so-called defect structures occur which influence the macroscopic properties of PVDF significantly. The amount of defect structures in the material is determined by the polymerization conditions. Here, the temperature dependence of the fraction of defect structures in PVDF obtained from polymerizations between 45 and 90 °C is reported. We utilized 19F-NMR spectroscopy to determine the fraction of defect structures as a function of temperature. To derive kinetic data, the polymerization of VDF is considered a quasi-copolymerization described by the Terminal Model involving four different propagation reactions. Based on the experimentally determined temperature-dependent fractions of defect structures, the known overall propagation rate coefficient, and taking into account the self-healing behavior of the macroradical, the Arrhenius parameters of the individual propagation rate coefficients were determined using the Monte Carlo methods. [ABSTRACT FROM AUTHOR]

Point defects induced by doping rare earth elements (RE) (Nd and Er) into a magnesium oxide host were investigated via classical atomistic simulations utilising the General Utility Lattice Program (GULP). Formation and association energies were calculated for the potential defect structures. Both isolated defects and defect complexes were considered. The most energetically favourable structures of defect complexes were found for rare-earth-doped and Li co-doped systems. The correlation between the association energy and the structure of the defect complex was investigated. The influences of Li were revealed with respect to energy and structure. The simulation results contribute to the understanding of the point defects of doped MgO and how Li influences the doping of rare earth elements in the MgO host. [ABSTRACT FROM AUTHOR]

High-entropy alloy nanoparticles (HEANs) possessing regulated defect structure and electron interaction exhibit a guideline for constructing multifunctional catalysts. However, the microstructure--activity relationship between active sites of HEANs for multifunctional electrocatalysts is rarely reported. In this work, HEANs distributed on multi-walled carbon nanotubes (HEAN/CNT) are prepared by Joule heating as an example to explain the mechanism of trifunctional electrocatalysis for oxygen reduction, oxygen evolution, and hydrogen evolution reaction. HEAN/CNT excels with unmatched stability, maintaining a 0.8V voltage window for 220 h in zinc-air batteries. Even after 20 h of water electrolysis, its performance remains undiminished, highlighting exceptional endurance and reliability. Moreover, the intrinsic characteristics of the defect structure and electron interaction for HEAN/CNT are investigated in detail. The electrocatalytic mechanism of trifunctional electrocatalysis of HEAN/CNT under different conditions is identified by in situ monitoring and theoretical calculation. Meanwhile, the electron interaction and adaptive regulation of active sites in the trifunctional electrocatalysis of HEANs were further verified by density functional theory. These findings could provide unique ideas for designing inexpensive multifunctional high-entropy electrocatalysts. [ABSTRACT FROM AUTHOR]

Lithium niobate is an artificial crystal which integrates electro-optic, acousto-optic, piezoelectric and nonlinear properties, and has been known as "optical silicon" or "photonic silicon". In recent years, with the rapid development of integrated photonics based on thin film lithium niobate, lithium niobate crystals have received more and more attention. However, lithium niobate is a typical non-stoichiometric crystal, it contains a large number of intrinsic defects, which seriously affects its characteristics. The lithium niobate lattice has good solid-solution to many impurity ions, moreover, its properties vary significantly with the types and concentrations of dopants. As with defect engineering of semiconductors such as silicon, defects have and will continue to have an important effect on crystal performance and integrated photonics based on thin film lithium niobate. This paper briefly reviews the defect structure of lithium niobate crystals, especially the recent progress on thin film lithium niobate crystals, including the intrinsic defect structure, extrinsic defect structure, characterization of defect structure, theoretical calculation of defect structure, and structure-activity relationship between defect structure and crystal properties. We hope it helpful to the current research of lithium niobate integrated photonics. [ABSTRACT FROM AUTHOR]

Four Zr: Dy: LiNbO3 crystals doped with different concentrations of Zr4+ (0, 1, 2, 4, mol%) have been grown by Czochraski technique. The effect of doping concentration of Zr4+ ions on the actual concentration of Zr4+ and Dy3+ ions in doped crystal was studied by the inductively coupled plasma-atomic emission spectrometry (ICP-AES). The results of X-ray diffraction and ultraviolet absorption spectroscopy showed that the Zr: Dy: LiNbO3 crystal still maintained the original lattice structure of the pure lithium niobate crystal, and the doped ions entered the crystal by preferential substitution of $ \hbox{Nb}^{4+}_{\rm Li} $ Nb Li 4 + , and doped ions entered the crystal When $ \hbox{Nb}^{4+}_{\rm Li} $ Nb Li 4 + is completely replaced, ions are doped to replace the normal Nb and Li positions into the crystal. The lattice constant with the increase of Zr content shows a trend of first becoming larger and then smaller. Finally, the optical uniformity of Zr4+ doped concentration on Zr: Dy: LiNbO3 crystals was studied by birefringence gradient method. The results showed that with the increase of Zr4+ ion doping concentration, the crystal optical uniformity of Zr: Dy: LiNbO3 gradually increased, and the optical uniformity reached the highest when doped at a concentration of 4 mol%. Based on the Li-site vacancy model, the experimental results are discussed in detail. [ABSTRACT FROM AUTHOR]

The effects of heat treatment with continuous laser radiation on samples of the Fe–18Cr–10Ni alloy of the austenitic-martensitic class that have undergone preliminary megaplastic torsional deformation in the Bridgman chamber are investigated. It is established that the combined application of deformation (deformation in the Bridgman chamber) and thermal (laser heating) effects to the alloy forms the structure of metastable austenite (γ phase), which differs from stable austenite in higher strength characteristics. The nature of this phenomenon is discussed. [ABSTRACT FROM AUTHOR]

Mg:Fe:Cu:LiNbO3 crystals with different [Li]/[Nb] ratios (0.946, 1.05, 1.20, 1.38) were prepared by the Czochralski method. The crystal structure and the occupancy of impurity ions were analyzed by X-ray diffraction (XRD). The effective segregation coefficient was analyzed by an inductively coupled plasma-atomic emission spectrometer (ICP-AES). The optical uniformity of the crystal is analyzed by birefringence gradient. The results show that the dopant ions do not change the crystal structure, and the concentration of dopant ions changes with the ratio of [Li]/[Nb]. The greater the ratio of [Li]/[Nb], the better the optical uniformity. Finally,we conclude that when the [Li]/[Nb] ratio approaches 1.20, the intrinsic defects of Mg:Fe:Cu:LiNbO3 crystals almost disappear and the crystals approach the stoichiometric ratio. When the [Li]/[Nb] ratio is 1.38, the optical uniformity of the crystal is the best. [ABSTRACT FROM AUTHOR]

A theoretical model for the formation of ultrasonic signals in metallic microcrystalline rods taking into account the metastable behavior of their defective states is proposed. The influence of metastable states of the defective structure of samples on the features of changes in their resonant frequencies in ultrasonic experiments of fast dynamics is analyzed. The increase in the Young's modulus and the dynamics of changes in resonant vibrations of rods made of aluminum alloy D16T under conditions of free relaxation are explained. Based on the results obtained, the concentration of metastable defects was estimated. [ABSTRACT FROM AUTHOR]

A theoretical model for the formation of ultrasonic signals in metallic microcrystalline rods taking into account the metastable behavior of their defective states is proposed. The influence of metastable states of the defective structure of samples on the features of changes in their resonant frequencies in ultrasonic experiments of fast dynamics is analyzed. The decrease in Young's modulus in such processes is explained. The correspondence between theoretical and experimental data is demonstrated for the example of resonant acoustic vibrations of rods made of aluminum alloy D16. [ABSTRACT FROM AUTHOR]

In this work, we simulate mechanical properties of pseudo-graphene crystals G5-7v1, G5-6-7v2, G4-8v1, G5-6-8v2, G5-6-8v4, G5-8v1, which include dense networks of wedge disclinations of alternate signs. The crystals were studied using the molecular dynamics method. The paper compares the values of elastic properties of graphene and pseudo-graphene obtained through AIREBO, Tersoff, and LCBOP interatomic interaction potentials. It shows that the application of these potentials in modeling pseudographene crystals is limited. The study concludes that it is necessary to update the existing potentials of interatomic interaction in allotropes of carbon or create a new one.

Sc: Yb: Ho: LiNbO3 crystals with various [Li]/[Nb] ratios (0.85, 0.94, 1.05, 1.20 and 1.38) were grown by Czochralski method. In this report, the effect of the [Li]/[Nb] ratio dependence of the doped element concentration and segregation coefficient was studied using an inductive coupled plasma-atomic emission spectrometer (ICP-AES). It was found that the change of the [Li]/[Nb] ratio will affect the concentration and the occupancy of the doped ions in the crystal. The structures of the crystals with different [Li]/[Nb] ratios are analyzed using X-ray diffraction patterns (XRD). It was found that doping elements do not change the crystal structure, and the crystal has the least defects when the [Li]/[Nb] ratio is 1.20. The optical uniformity of crystals was measured by birefringence gradient method. The results show that the optical uniformity of the crystal is significantly enhanced as the [Li]/[Nb] ratio increases. [ABSTRACT FROM AUTHOR]

Borides are usually hard and brittle materials; however, we report the synthesis of superplastic nanostructured NdB6 ceramic powders, counter to the conventional wisdom that borides are always brittle. We investigate that through strain engineering, NdB6 can be made extremely ductile if the lattice is compressively strained and highly defected, based on transmission electron microscopy (TEM) and density functional theory (DFT) calculations. In this study, the synthesis conditions were designed based on CALPHAD modelling, and the superplastic NdB6 powders were successfully obtained through mechanochemical synthesis (MCS) of Nd2O3, B2O3 and Mg initial materials in a high-energy ball mill. Following MCS, the powders were purified in a hydrochloric acid (HCl) containing aqueous solution in order to leach out MgO by-product. The purified powders were characterized using X-ray diffractometry (XRD), Helium (He) gas pycnometry, scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), particle size analysis (PSA) and magnetometry techniques, which demonstrated NdB6 nanoparticles with an average particle size of 118 nm belonging paramagnetic behavior at cryogenic temperatures. DFT calculations have been carried out through to investigate the structural, mechanical, electronic, optical, thermodynamic and magnetic properties of NdB6. The impact of various defects was examined, which revealed the significance of boron vacancies and compressive strains in the superplastic form of NdB6.

We propose a low loss and high selectivity bandpass filter with defected structure on GaN-on-Silicon. GaN-on-Si exhibits a high insertion loss due to the presence of parasitic channels at the AlN/Si interface. It is necessary to strengthen the coupling between the resonators to achieve a low loss. However, this results in weaker suppression of adjacent channels and lower selectivity of frequencies. The designed filter consists of square spiral defect structure resonators and a step impedance resonator, which provides tunable transmission zero and facilitates the adjustment of pass band. With an interdigitated capacitor, at a frequency span from 3.3 to 4.9 GHz, the proposed filter has a low insertion loss of 2.71dB and improves the suppression of adjacent channel (5.8 GHz) by 11.2 dB compared to the traditional SIR filter. The out-of-band suppression of the filter is better than 15.93 dB at 20 GHz. Compared to the traditional SIR filter, the proposed filter achieves a steep transition zone, and an out-of-band rejection reduction by at least 6.6 dB.

Lithium tantalate (LiTaO3, or LT) crystal is widely used in optical applications, infrared detection, and acoustic surface wave devices because of its excellent piezoelectric, pyroelectric, and nonlinear optical properties. In this paper, we discuss the defect structure of LT; the preparation method for LT; the influence of doping on LT; and LT's application in optical, acoustic, and electrical devices. We mainly analyzed the structure and physical properties of LT crystal, the preparation of LT crystal and LT thin films, the periodic polarization of LT crystal, the reduction of LT wafers, and the application potential of LT crystals in lasers and acoustic surface filters according to the most recent research. We also provide an overview of future research directions for LT in the fields of acoustics, optics, and other fields. The applications of LT in 5G, 6G, SAW filters, nonlinear optical devices, and waveguides are expected to provide additional breakthroughs. [ABSTRACT FROM AUTHOR]

Two series of LiNbO3:Mg:B crystals have been grown and studied. Two doping methods—have been used. The crystals—have been co-doped with Mg and a non-metallic dopant, B. The physicochemical features of the growth—have been considered for LiNbO3:Mg:B crystals obtained from a boron-doped melt. The charge—has been prepared using different technologies: homogeneous (HG) and solid-phase (SP) doping. The same two methods have been used to grow single-doped LiNbO3:Mg crystals. A control near-stoichiometric (NSLN) crystal—has been grown via the HTTSSG (high-temperature top-seeded solution growth) method from a congruent melt (Li/Nb ≈ 0.946) with 5.5 wt% K2O. The characteristics of the LiNbO3:Mg:B crystals—have been compared with those of the LiNbO3:Mg and NSLN crystals. Physicochemical and structural reasons have been established for the differences in the distribution coefficients of magnesium (KD) during the growth of the HG- and SP-doped LiNbO3:B:Mg and LiNbO3:Mg crystals. The optical characteristics of the LiNbO3:B:Mg crystals—have been studied via optical spectroscopy, laser conoscopy and photoinduced light scattering (PILS). The influence of boron on the microstructure, compositional and optical uniformities and optical damage resistance of the LiNbO3:Mg:B crystals—has been estimated. Optimal technological approaches to growing optically uniform LiNbO3:B:Mg crystals have been determined. LiNbO3:Mg:B crystals have been shown to have a significant advantage over the commercially used LiNbO3:Mg crystals since large LiNbO3:Mg:B crystals can be grown without stripes. Such stripes usually appear perpendicular to the growth axis. In addition, the photorefractive effect is suppressed in LiNbO3:Mg:B crystals at lower magnesium concentrations ([Mg] ≈ 2.5 mol%) than in LiNbO3:Mg ([Mg] ≈ 5.5 mol%). [ABSTRACT FROM AUTHOR]

Present study investigates the response of various coloured variants of natural fluorite (CaF 2) to 10 MeV electron beam irradiation at accumulated dose of 5–10 MGy. The fluorite specimens did not show any post irradiation radioactivity. However, after irradiation the specimens developed purple colouration of different shades depending on the dose. In-depth characterization of the as-received and irradiated specimens using XPS and Raman spectroscopy confirm the relocation of fluorine (F) anions at interstitial sites and formation of metallic calcium (Ca). The calculated displacement cross sections for F and Ca indicate that it is easier to form fluorine anion interstitials within lattice structure. However, the estimated lower fraction of interstitial fluorine (∼14%) as compared to metallic Ca (>50%) is attributed to their surface diffusion and desorption. Electron irradiation was found to cause photoluminescence quenching in all the CaF 2 specimens that is likely caused by a radiation-induced formation of competing recombination channels. • Cationic and anionic sub-lattice defects in the co-located natural CaF 2 under 10 MeV electron irradiation were studied. • Increase in metallic Ca fraction was higher than the increase in F-ions displaced from their lattice sites. • Mechanism for radiation damage is proposed. • Effect of irradiation on luminescence properties is elucidated. [ABSTRACT FROM AUTHOR]

The lack of systematic research on the phase structure, defect structure, and polarization mechanism hinders the full comprehension of the colossal permittivity (CP) behavior for SrTiO 3 -based ceramics. For this purpose, Ta-doped SrTiO 3 -based ceramics were synthesized in an N 2 atmosphere with a traditional method. When the appropriate amount of Ta was doped, colossal permittivity (ԑ r ∼ 62505), low dielectric loss (tanδ ∼ 0.07), as well as excellent temperature stability (−70 °C–180 °C, ΔC/C 25°C ≤ ±15%) were obtained in the Sr 0.996 Ta 0.004 TiO 3 ceramic. The relationship between Ta doping, polarization mechanism, and dielectric performance was systematically researched according to experimental analysis and theoretical calculations. The first-principle calculations indicate that the Ta5+ ion prefers to replace the Sr-site. The defect dipoles and oxygen vacancies formed by heterogeneous-ion doping play an active role in regulating the dielectric performance of ceramics. In addition, the interface barrier layer capacitance (IBLC) effect associated with semi-conductive grains and insulating grain boundaries is the primary origin of colossal permittivity for Sr 1-x Ta x TiO 3 ceramics. The polarization mechanism and defect structure proposed in the study can be extended to the research of SrTiO 3 CP ceramics. The results have a good development prospect in colossal permittivity (CP) materials. [ABSTRACT FROM AUTHOR]

The comprehensive control of dielectric properties and temperature stability is the focus of BaTiO 3 -based ceramics with non-reducibility. For this purpose, BaTiO 3 –0.02MgO–0.02Y 2 O 3 –0.04CaZrO 3 –xMnO 2 (x = 0, 0.005, 0.01 and 0.015) ceramics were prepared by the solid-state method and sintered in a reducing atmosphere. When x = 1.5 mol%, high dielectric constant (ԑ r ∼ 3644), large insulation resistivity (ρ v ∼ 2.07 × 1011 Ω cm), and low dielectric loss (tanδ ∼ 0.011) were obtained in ceramics, which demonstrated the superior potential of current studies. The effects of multivalent Mn-ion doping on the phase transition, dielectric characteristics, and defect polarization were systematically investigated based on the experimental results and first-principle calculations. The change of dielectric properties was related to the formation of new defect dipoles ([ M n T i ′ − Y B a • ] and [ M n T i ″ − 2 Y B a • ]). According to the first-principle calculations, the deformation of ceramic structures and the nonuniform distribution of electron density lead to the weakening of chemical bonds and the enhancement of carrier transitions. The interfacial polarization associated with the long-range hopping of oxygen vacancies is the main source of high dielectric constant for Mn15 ceramic samples. Furthermore, all ceramics showed excellent temperature stability and satisfied the EIA X8R standard (−55 °C–150 °C, ΔC/C 25°C ≤ ±15%), which can be explained by the "core-shell" structure. The effect of internal defect structure on polarization mode presented in this work can be applied to the study of BaTiO 3 -based dielectric ceramics. The results have excellent application potential in the BME-MLCC industry. [ABSTRACT FROM AUTHOR]

Developing high-performance adsorbents for heavy metal (Cr (VI)) removal is essential for sustainable environments, but it is still challenging. Herein, a simple solvothermal method was proposed to fabricate Zr-MOFs (UiO-66), which was innovatively modified by amino groups to enhance the adsorption capacity of Cr (VI). The effects of the content of amino-functionalized ligands on the adsorption capacity and the influence of adsorbent content, solution pH, adsorption time, and adsorption temperature on the adsorption process were systematically investigated. Importantly, the pore structure and defect structure of UiO-66 can be finely regulated by adjusting the amino modification process. The adsorption process was fitted and analyzed using the kinetic model and the isotherm model. Impressively, the adsorption capacity of the amino-modified UiO-66 (UiO-66-NH2) was greatly improved. These findings indicate that the surface functional group modification of MOFs is a promising method for adjusting their structure and improving their adsorption capacity. [ABSTRACT FROM AUTHOR]

Transient behaviors of molecular orientation field of nematic liquid crystal (4-n-4’-octylcyanobiphenyl) under shear flows between concentric cylinders have been numerically investigated using the Leslie-Ericksen continuum theory in which the molecular orientation is represented with a unit vector, called the director. As well as the rotation speed of an inner cylinder, the director anchoring conditions at the inner and outer cylinders are chosen as simulation parameters to obtain four different cases of director initial profiles, which are homeotropic, hybrid, planar, and twist cases. After the imposition of the shear flow, the director start rotating within the shear plane, increasing the curvature energy of the director field. When the energy exceeds a certain critical value, the director start escaping from the shear plane, called the out-of-plane behavior. Because the escaping direction (i.e., either +z or -z directions) is the stochastic choice, the director field is randomly separated into the positive and negative out-of-plane regions. Then, the spatially distributed two out-of-plane regions are transformed into line defect structures. The spatial patterns of the out-of-plane regions and the line defect structures strongly depends on the director anchoring conditions, and no patterns are found for the twist case. The evolutions of torques of the inner cylinder is also estimated from the simulation results for four cases, and the oscillatory behavior of the torque is found for the homeotropic case.

Point defects induced by doping rare earth elements (RE) (Nd and Er) into a magnesium oxide host were investigated via classical atomistic simulations utilising the General Utility Lattice Program (GULP). Formation and association energies were calculated for the potential defect structures. Both isolated defects and defect complexes were considered. The most energetically favourable structures of defect complexes were found for rare-earth-doped and Li co-doped systems. The correlation between the association energy and the structure of the defect complex was investigated. The influences of Li were revealed with respect to energy and structure. The simulation results contribute to the understanding of the point defects of doped MgO and how Li influences the doping of rare earth elements in the MgO host.

Geometric imperfections are understood to play an essential part in the buckling of a thin shell, but how multiple defects interact to control the onset of failure remains unclear. Here, we examine the failure of real cylindrical shells by experimentally poking soda cans with a large imparted dimple. By high-speed imaging of the can's surface, the initiation of buckling from axial loading is directly observed, revealing that larger dimples tend to set the initial buckling location. However, the influence of the shell's background geometric imperfections can still occasionally dominate, causing initiation to occur far from the dimple. In this situation, probing at the dimple leads to an over-prediction of the axial capacity. Using finite-element simulations, we understand our experimental results as a competition between the large dimple and the shell's inherent defect structure. In our simulations, we empirically observe a deformation-based criterion that connects the ideal poking location to the initiation site. This article is part of the theme issue 'Probing and dynamics of shock sensitive shells'. [ABSTRACT FROM AUTHOR]

In this paper, structural features of the NiO-SiO2 nanocrystalline catalyst synthesized by the sol-gel method were studied by X-ray diffraction (XRD), high-resolution transmission electron microscopy (TEM), and differential dissolution (DD). The XRD pattern of NiO-SiO2 significantly differs from the "ideal" NiO pattern: the peaks of the NiO-like phase are asymmetric, especially the 111 diffraction peak. The NiO-SiO2 nanocrystalline catalyst was investigated by means of XRD simulations based on two approaches: conventional Rietveld analysis and statistical models of 1D disordered crystals. Through a direct simulation of XRD profiles, structural information is extracted from both the Bragg and diffuse scattering. XRD simulations showed that the asymmetry of all the diffraction peaks is due to the presence of two NiO-like oxides with different lattice constants and different average sizes: ~90 wt% of mixed Ni-Si oxide (Ni:Si = 0.14:0.86) with average crystallite sizes (D ~ 27.5 Å) and ~10 wt% of pure NiO (D ~ 50 Å). The high asymmetry of the 111 diffraction peak is due to the appearance of diffuse scattering caused by the inclusion of tetrahedral SiO2 layers between octahedral NiO layers. Such methods as TEM and DD were applied as independent criteria to prove the structural model, and the results obtained confirm the formation of mixed Ni-Si oxide. [ABSTRACT FROM AUTHOR]

A series of Zr:Fe:Cu:LiNbO3 crystals with distinct Zr4+ ion doping concentrations (0, 2, and 4 mol%) were grown using the Czochralski method. Subsequently, the segregation coefficient of doped ions in the crystal was analyzed by an inductively coupled plasma-atomic emission spectrometer. The lattice constant and defect structure of the crystal were measured by X-ray powder diffraction. The light-induced scattering of Zr:Fe:Cu:LiNbO3 crystal was analyzed by the threshold effect of incident exposure energy flux and the same as the change in Zr4+ ion doping concentration. When the Zr4+ ion concentration changes to 4 mol%, the exposure energy was close to 811.37 J/cm2, which is about 192 times that of the 0 mol% Zr4+. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bi 2 MoO 6 @sRuO 2 heterojunction exhibits enhanced photocatalytic activity under NIR irradiation. • Defect engineering via GSH treatment improves ROS generation of Bi 2 MoO 6 @sRuO 2. • Bi 2 MoO 6 @sRuO 2 shows potent antibacterial activity against E. coli and MRSA , including biofilms. • In vivo , Bi 2 MoO 6 @sRuO 2 promotes wound healing and reduces inflammation in infected wounds. • Bi 2 MoO 6 @sRuO 2 offers promising non-antibiotic strategy for multidrug-resistant infection. Antibacterial Photocatalytic Therapy (APCT) is a promising therapeutic strategy for the treatment of bacterial infections, but it faces challenges such as low light utilization efficiency, insufficient reactive oxygen species (ROS) generation, and limited antibacterial efficacy. In this work, a novel Bi 2 MoO 6 @sRuO 2 @HA heterojunction (BMOsRH heterojunction) was constructed to address these limitations. The key innovation of this heterojunction lies in the introduction of sRuO 2 , which provides an effective charge carrier transfer interface for separated electrons and holes in Bi 2 MoO 6 , significantly delaying electron-hole recombination and promoting redox reactions that generate highly toxic ROS, thus enhancing antibacterial effects. Density functional theory (DFT) calculations indicated that BMOsRH possesses photocatalytic activity triply enhanced by near-infrared light absorption, defects, and the heterojunction. Consequently, under the combined action of near-infrared light and hydrogen peroxide, BMOsRH exhibited nearly 100 % antimicrobial activity against Escherichia coli (E. coli) and Methicillin-resistant Staphylococcus aureus (MRSA), and could also disrupt their biofilms. Furthermore, in mouse wound and abscess models of MRSA infection, BMOsRH effectively eliminated bacteria via mild photothermal therapy and significantly downregulated the inflammatory factors IL-1 β and TNF- α , promoting rapid wound healing. In summary, this light-controlled therapeutic strategy shows great potential for antibacterial applications. [ABSTRACT FROM AUTHOR]

The defective structure of p-CdTe:Cl single crystals and MoOx/p-CdTe/MoOx heterostructures were investigated by high-resolution X-wave diffractometry methods. Different models of dislocation systems were used and the dislocation densities were estimated from the Williamson-Hall plot. It is noted that significant deformations of the mismatch in the transition layer negatively affect the current–voltage characteristics of heterostructures.

Lithium niobate is a ferro- and piezoelectric material with excellent optical properties and a wide variety of applications. The defect structures of congruent and Mg-doped crystals are still under intense discussion. In this work, undoped lithium niobate and magnesium-doped lithium niobate grown from congruent melt with the addition of 0 to 9 mol% MgO were investigated by infrared absorption, establishing the dependence of the absorbance on the Mg-doping level in two bands related to OH − stretching vibrations. The absorption band at 3485 cm − 1 peaks at a MgO concentration in melt of 1 mol% and vanishes for MgO concentrations above the threshold level for optical damage suppression (4.8 mol%). A corresponding peak occurs in the minimum yield of the 7 Li(p, α) 4 He reaction during ion channeling measurements, indicating a maximum of disorder in the Li sublattice. A possible explanation for this correlation is the attribution of this absorption band to ilmenite stacking fault sequences instead of isolated Nb Li antisites in undoped and low-doped material. On the other hand, the OH − absorption band at 3535 cm − 1 stays weak up to the MgO concentration threshold, and then increases, hinting to a defect related to the increase of vacancies due to the lack of charge compensation. [ABSTRACT FROM AUTHOR]

Self-assembled MnO2 nanowires were hydrothermally synthesized and electrically characterized under different conditions. The nanowires were approximately 3–10 µm long and about 20–100 nm in diameter. Single nanowires were aligned perpendicularly across two parallel gold electrode transducers by means of the dielectrophoresis (DEP) technique. Resistivity changes in synthetic air, nitrogen, and NO2 were tested in a range from 100 °C up to 300 °C. The resistivity changes were observed to account for the oxygen reduction on the NWs’ surface as the electrons were moving from the NWs to the oxygen. The resistivity was explored through a constant current arrangement test. Based on the resistivity changes, electrical properties, such as activation energy and type of semiconductor, were estimated.

Zn (1, 3, 5, 7 mol.%): Dy: LiNbO3 crystals were prepared by the traditional vertical pull-up method. The effective segregation coefficients of Zn 2 + and Dy 3 + were found to decrease with increasing Zn 2 + concentration using ICP-AES analysis test. The lattice size was found to increase first and then decrease using XRD analysis test. The absorption spectrum was found blue shifted and produced two peaks using IR. Research shows that when the Zn content reaches or exceeds the threshold value, Nb Li 4 + is replaced completely, and Zn occupies the Li and Nb positions of lithium niobate, thus introducing the non-intrinsic defect Zn Li + and Zn Nb 3 − . Both defects are able to form 3Zn Li + − Zn Nb 3 − charge self-compensating defect groups and inhibit the charge transport process and thus will greatly increase the photodamage resistance. [ABSTRACT FROM AUTHOR]

Twist grain boundary (TGB) phases represent liquid crystalline systems with a regular array of defects. In our research, we studied a compound with a stable TGBC phase and pursued its structure using various experimental techniques. Using AFM microscope, we observed the surface of the smectic film and detected a periodic relief. We found that the displacement amplitude is a few nanometres, with a periodicity of about 500 nm. Such periodicity is in accordance with the periodicity of the TGBC blocks' rotation estimated by polarising microscopy. The surface modulation is explained by the deformation of the TGBC structure, which is created on TGBC films. A simplified model interpreting the observed smectic surface displacement as the consequence of rotating TGBC blocks inside the sample is proposed. TGBC blocks deform differently depending on their orientation with respect to the force acting by the tip of the AFM microscope cantilever probing the smectic surface. [ABSTRACT FROM AUTHOR]

Structural features and catalytic properties of silver and iron binary oxide AgFeO2 in the СО oxidation reaction are investigated. Binary oxide samples are obtained by coprecipitation and hydrothermal synthesis techniques at different temperatures. In the temperature range of 140-180 °С, well crystallized AgFeO2 particles are formed primarily with a 3R polytype structure (~90%), and at T = 60-120 °С highly dispersed particles with a developed defect structure are obtained. It is shown that calculated X-ray diffraction patterns of models of delafossite crystals with microtwinning are well consistent with experimental curves. Binary oxide AgFeO2 samples demonstrate a high activity in the СО oxidation reaction, which increases with a decrease in the synthesis temperature. The highest specific catalytic activity is found for highly dispersed samples with a developed defect structure. During catalytic experiments the effect of the reaction medium modifies the surface composition due to the partial exit of silver from the delafossite structure. [ABSTRACT FROM AUTHOR]

Cu-doped MnO2 with the composition of Mn1-xCuxO2 (x = 0–0.15) was synthesized and characterized. The synthesis was carried out by hydrothermal method at 140 °C for 5 h of reaction dwell time. The characterizations include X-Ray Diffraction (XRD), Microscopy, X-ray Absorption Spectroscopy (XAS), and Impedance complex analysis. It was revealed that all samples have nanorod morphology. Their size increases with the increasing dopant. Additionally, K ions are detected by EDX. All samples pose α-MnO2 type structures performing (2 × 2) and (1 × 1) tunnels permitting large ions incorporated and oxygen deficiency. The octahedron was distorted to elongate up to x = 0.10, then compressed for x = 0.15, inducing the Jan Teller effect. Oxidation state analysis revealed that the manganese has Mn3+ and Mn4+, while the copper is mainly attributed to Cu2+ and Cu3+ respectively. The small ionic size and highly oxidized Cu3+ substitute Mn4+, while Cu2+ substitutes Mn3+ or simultaneously with the larger K+ incorporated in the tunnel. Accordingly, the defects to exist in the sample, namely CuMn′, MnMn′, VO••, and e′. Electrical characterization at room temperature revealed that the conductivity of Cu-doped MnO2 is dominated by electrons influenced by the various oxidation state of the cations in the octahedron sites, while space charges dominate the dielectric response.

Lithium tantalate (LiTaO3, or LT) crystal is widely used in optical applications, infrared detection, and acoustic surface wave devices because of its excellent piezoelectric, pyroelectric, and nonlinear optical properties. In this paper, we discuss the defect structure of LT; the preparation method for LT; the influence of doping on LT; and LT’s application in optical, acoustic, and electrical devices. We mainly analyzed the structure and physical properties of LT crystal, the preparation of LT crystal and LT thin films, the periodic polarization of LT crystal, the reduction of LT wafers, and the application potential of LT crystals in lasers and acoustic surface filters according to the most recent research. We also provide an overview of future research directions for LT in the fields of acoustics, optics, and other fields. The applications of LT in 5G, 6G, SAW filters, nonlinear optical devices, and waveguides are expected to provide additional breakthroughs.

[Display omitted] • The Nd 0.06 Ni catalyst demonstrates enhanced activity and improved resistance to NO x for De-N 2 O. • The edge dislocation and defect structure enhance the amount of oxygen vacancies. • The addition of Nd leads to a significant increase in active sites, from 78.68 μmol g−1 to 174.34 μmol g−1. • In the presence of NO x , Nd 0.06 Ni exhibits a higher TOF compared to NiO. In the field of catalytic N 2 O decomposition, it is imperative to develop low-temperature De-N 2 O catalysts with effective NO x tolerance. Herein, Nd 0.06 Ni catalyst was synthesized by coprecipitation method, incorporating additive Nd into NiO to enhance its catalytic performance. Characterization results indicated that the introduction of Nd into catalyst not only reduced the crystallite size of NiO, but also induced the formation of edge dislocations, defects, and synchronously weakened Ni-O bond. Additionally, the distinctive interaction between Nd and NiO endows enhanced NO x tolerance for Nd 0.06 Ni compared with pure NiO. Consequently, the T 50 for De-N 2 O over Nd 0.06 Ni was 330 °C under simultaneous feeding of 2000 ppmv N 2 O, 5 vol% O 2 , and 100 ppmv NO, which was much lower than that of pure NiO (430 °C). Moreover, it was calculated that the E a decreased from 82 to 74 kJ·mol−1, and the TOF increased from 1.82 × 10-3 to 4.39 × 10-3 s−1 at 350 °C when comparing pure NiO with Nd 0.06 Ni. In the presence of NO x , the TOF of the reaction for Nd 0.06 Ni was discovered to be 39-fold higher compared with pure NiO. Furthermore, Nd 0.06 Ni exhibited remarkable thermal stability in an environment containing O 2 , NO, and H 2 O, maintaining ∼ 63% N 2 O conversion at 400 °C. [ABSTRACT FROM AUTHOR]

Herein, the growth mechanism and defect structure of GaN‐based nanowire multiple‐quantum‐shells (NW‐MQSs) with cap layers combining tunnel junctions and n‐GaN are investigated in detail. In the NW‐MQS structure, defect structures are formed in three regions: (i) From the c‐plane active layer at the tip of NW because of the low crystal quality of the active layer. (ii) Basal‐plane stacking faults (BSFs) with partial dislocations (PDs) are generated from the m‐planes of the NW‐MQSs; these defects are triggered by the silicon nitride (SiNx) formed on the NW surface. While some defects terminate because of the half loop formed by the PDs along the lateral growth of cap layers, others terminate at the coalesced region of the cap layers grown from adjacent MQSs. (iii) Line defects due to low‐angle grain boundaries and planar defects due to the BSFs in region (ii) are formed in the region wherein cap layers coalesce. The defects reaching the surface of the cap layers predominantly depend on the number of defects generated from the c‐plane active layers in region (i). The growth mode and propagation mechanism of such defects are associated, and a method for realizing optical devices based on the high‐quality NW‐MQS structures is discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] The polycrystalline samples of Cu2 – δ SrSnS4 with a trigonal structure were prepared by solid-phase ampoule synthesis with a long annealing time (1944 h), and their crystal lattice parameters were refined and Raman spectra were obtained. For the first time, the effect of defect structure on the lifetimes of photogenerated current carriers in the polycrystalline powders was examined by combining time-resolved microwave photoconductivity and cathodoluminescence methods. A significant increase in the lifetimes during the conversion of Cu 2 SrSnS 4 into Cu 1.9 SrSnS 4 was found, which was probably due to changes in the defect structure. [ABSTRACT FROM AUTHOR]

Ti-related oxide ceramics often exhibit excellent microwave dielectric properties and are widely applied in the microwave communication field. However, their microwave dielectric properties are often influenced by unstable defects, which are caused by the relatively low oxygen partial pressure at high sintering temperatures. In this work, Al 2 O 3 was introduced to improve the defect structures of the 0.85CeO 2 -0.15TiO 2 ceramics. According to the XPS pattern and AC conductivity analysis, Al 2 O 3 doping could stabilize the valence state of Ti but increase the oxygen vacancy concentration. Q × f first increased and then decreased as the Al 2 O 3 content increased. The highest Q × f value of 54361 GHz was obtained for the CTA0.015 sample sintered at 1275 °C, as well as the ε r of 29.41 and τ f of +7.8 ppm/°C. Finally, the CTA0.015 sample was used to prepare a microstrip antenna via the screen-printing process, which exhibited a good temperature-independent resonant frequency and indicated good application prospects. [ABSTRACT FROM AUTHOR]

Abstract The thermal stability and fatigue resistance of piezoelectric ceramics are of great importance for industrialized application. In this study, the electrical properties of (0.99-x)(K0.48Na0.52)(Nb0.975Sb0.025)O3-0.01CaZrO3-x (Bi0.5Na0.5)HfO3 ceramics are investigated. When x = 0.03, the ceramics exhibit the optimal electrical properties at room temperature and high Curie temperature (T C = 253 °C). In addition, the ceramic has outstanding thermal stability ( $$d_{33}^*$$ d 33 * ≈ 301 pm/V at 160 °C) and fatigue resistance (variation of P r and $$d_{33}^*$$ d 33 * ~10% after 104 electrical cycles). Subsequently, the defect configuration and crystal structure of the ceramics are studied by X-ray diffraction, temperature-dielectric property curves and impedance analysis. On one hand, the doping (Bi0.5Na0.5)HfO3 makes the dielectric constant peaks flatten. On the other hand, the defect concentration and migration are obviously depressed in the doped ceramics. Both of them can enhance the piezoelectrical properties and improve the temperature and cycling reliabilities. The present study reveals that the good piezoelectric properties can be obtained in 0.96(K0.48Na0.52)(Nb0.975Sb0.025)O3-0.01CaZrO3-0.03(Bi0.5Na0.5) HfO3 ceramics.