Search

The influence of Eu doping (0.5, 1 and 2 mol.%) and annealing in an oxygen-deficient atmosphere on the structure and optical properties of SnO2 nanoparticles were investigated in relation to electronic structure. The X-ray diffraction (XRD) patterns revealed single-phase tetragonal rutile structure for both synthesized and annealed Eu-doped SnO2 samples, except for the annealed sample with 2 mol.% Eu. The results of X-ray photoelectron spectroscopy (XPS) emphasized that europium incorporated into the SnO2 host lattice with an oxidation state of 3+, which was accompanied by the formation of oxygen vacancies under cation substitution of tetravalent Sn. Moreover, XPS spectra showed the O/Sn ratio, which has been reduced under annealing for creating additional oxygen vacancies. The pulse cathodoluminescence (PCL) demonstrated the concentration dependence of Eu site symmetry. Combination of XRD, XPS and PCL revealed that Eu doping and following annealing induce strongly disordering of the SnO2 crystal lattice. Our findings provide new insight into the interaction of rare-earth metals (Eu) with host SnO2 matrix and new evidence for the importance of oxygen vacancies for optical and electronic structure formation. [ABSTRACT FROM AUTHOR]

This study investigated changes in the crystal lattice, tribological properties and friction mechanism of AISI 316 steel irradiated with swift 160 MeV xenon ions. The irradiation process caused the increased roughness of the steel surface and the swelling of the material. The thickness of the irradiated layer increased by about 13 nm. Following irradiation with the fluences 2.5 × 1014 and 3.2 × 1014 (Xe24+/cm2), martensite formed in the surface layer. Fluctuating changes were also observed with respect to the coefficient of friction and the degree of wear of the AISI 316 steel samples. Irradiation also increased the microhardness of the steel. [ABSTRACT FROM AUTHOR]

Amorphous films are formed on substrates at room temperature in the process of anodic oxidation of niobium foil. The studies were carried out using methods of electron diffraction and "in situ" transmission electron microscopy (TEM) with video recording of structural changes. It was found that electron beam irradiation of the film with a dose rate (4–7)·104 e−/Å2·s inside the column of the electron microscope causes its layer polymorphous crystallization (LPC) with the formation of Nb2O5 crystals with hexagonal lattice. The dimensionless parameter of the relative crystallization length δ0≈ 5000 − 7000. The dependence on time of the crystal diameter is described by a power function with exponents of 1.55, 1.1 and 1.3. According to this the dependence of the fraction of the crystalline phase on time is described by a power function with exponents of 3.1, 2.2 and 2.6. This non-quadratic nature is explained with the formation of a domain superstructure in the low-temperature modification of α-Nb2O5 and phenomenon of polyamorphism in amorphous films. [ABSTRACT FROM AUTHOR]

Spin‐crossover (SCO) complexes have drawn significant attention for the possibility to photoswitch their electronic spin state on a sub‐picosecond timescale at the molecular level. However, the multi‐step mechanism of laser‐pulse‐induced switching in solid state is not yet fully understood. Here, time‐resolved synchrotron X‐ray diffraction is used to follow the dynamics of the crystal lattice in response to a picosecond laser excitation in nanometric thin films of the SCO complex [Fe(HB(1,2,4‐triazol‐1‐yl)3)2]. The observed structural dynamics unambiguously reveal a lattice expansion on the 100 picosecond timescale, which is temporally decoupled both from the ultrafast molecular photoswitching process (occurring within 100 fs) and from the delayed, thermo‐elastic (Arrhenius‐driven) conversion (taking place ≈10 ns). These time‐separated dynamics are also manifested by the observation of damped acoustic oscillations in the time evolution of the lattice volume, whereas no such oscillations are observed in the electronic spin‐state dynamics. Overall, these results suggest the existence of a universal behavior whereby the intramolecular energy barrier between low‐spin and high‐spin states acts as an intrinsic dynamical bottleneck in the out‐of‐equilibrium spin‐state switching dynamics of SCO materials. [ABSTRACT FROM AUTHOR]

Mg metal anode‐based battery is a more sustainable, lower cost, and higher energy density alternative to Li‐ion. However, this battery chemistry also faces several challenges associated with the high charge density of Mg2+, including achieving high reversibility and low voltage hysteresis for Mg metal plating/stripping. While significant improvements are achieved in last decades, they involve rather complex electrolyte formulations and/or Mg salts difficult to produce, and the use of unpractical substrates such as platinum. Here, significant improvement in terms of Mg plating kinetics is achieved in electrolytes containing commercial magnesium bis(trifluoromethanesulfonyl)imide salt (Mg(TFSI)2) by using titanium substrate with similar crystal structure and lattice parameter as Mg leading to lower nucleation overpotential. Low salt concentration electrolyte and addition of dibutyl magnesium (Mg(butyl)2) also enable the formation of thinner interphase, richer in solvent based decomposition products, further improving Mg plating kinetics. This work highlights the complex role of Mg(butyl)2, often considered as a simple drying agent, and how it impacts ion solvation favoring the mobility of electroactive cationic species, paving the way toward better electrolyte design with improved cation transference number. [ABSTRACT FROM AUTHOR]

A narrow-band green emitting K3Tb(PO4)2 phosphor has been synthesized by a novel single-crystal growth approach involving the application of an inert flux. Its structural and spectroscopic peculiarities have been systematically studied by means of single-crystal X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy analysis, and diffuse reflectance, infrared and photoluminescence spectroscopy. The layered framework of the title compound is organized by linking together slightly distorted phosphate tetrahedra with non-condensed TbO7 polyhedra into [Tb(PO4)2]3− sheets interconnected by potassium cations. K3Tb(PO4)2 reveals an intense slow green photoluminescence (PL) (decay time constant τ is near 2.6 ms) under excitation in the range from VUV (100 nm) up to blue light (484 nm). Intensive narrow lines of the 5D4 → 7F6-0 (4f8 → 4f8) radiative transitions in Tb3+ ions form the PL spectra. Besides, fast violet PL (time constant τ < 20 ns) occurs under PL excitations in a narrow range from 250 to 325 nm. Dependencies of the PL quantum yield, and the green and violet PL decays on the excitation wavelength have been analyzed taking into account the multi-phonons, cross-relaxation processes and exciting light absorption by the inherent defects in the K3Tb(PO4)2 crystal lattice. The dependency of the complex characteristics of PL quantum yield on the excitation wavelength and violet photoluminescence is ascribed to the formation of Tb4+ ions. The color coordinates and color purity of the emission were estimated for the cases of PL excitation in the 160–371 nm spectral range. It has been shown that these characteristics are similar to or even better than those reported for conventional commercial green phosphors. The high values of correlated color temperature (T > 4863 K) of the emission indicates the potential use of K3Tb(PO4)2 for enhancing cold-light emitting devices. [ABSTRACT FROM AUTHOR]

Exploring the organic molecular structural features and supramolecular interactions provide basis for developing stimuli-responsive organic solid-state fluorescent materials. Herein, we have synthesized methoxyphenyl-substituted carbazole-based π-conjugated derivatives (Cz-MN, Cz-ECA, Cz-CA, Cz-CAA and Cz-NBA) with different acceptor units and investigated their influence on solid-state fluorescence. All five compounds showed aggregation-induced emission (AIE) in the solid state with acceptor-dependent tunable fluorescence from 488 to 602 nm (quantum yield (Φf) = 7.2 to 1.9%). Cz-ECA exhibited blue-shifted fluorescence, whereas Cz-NBA showed red-shifted fluorescence. Cz-MN, Cz-ECA and Cz-CA revealed relatively strong solid-state fluorescence compared to Cz-CAA and Cz-NBA. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) calculations suggested intramolecular charge transfer (ICT) from the carbazole donor to the acceptor unit. Mechanofluorochromic studies of Cz-MN and Cz-ECA showed self-reversible fluorescence switching but the other three AIEgens did not show any stimuli–response. Single crystal structural analysis of Cz-MN, Cz-ECA and Cz-CA showed twisted molecular conformations with different intermolecular interactions. Both Cz-MN and Cz-ECA did not show any strong intermolecular interactions in the crystal lattice. In contrast, Cz-CA exhibited strong amide–amide complementary H-bonding and an extended network structure. Hence, the twisted molecular conformation and the absence of strong intermolecular interactions in Cz-MN and Cz-ECA contributed to self-reversible mechanofluorochromism (MFC). Thus, the present study is expected to provide further insight to design AIEgens with stimuli-responsive self-reversible fluorescent materials. [ABSTRACT FROM AUTHOR]

Background: Sacubitril/valsartan, marketed as Azmarda (manufactured by the innovator company) is a cocrystal consisting 6 sacubitril and valsartan molecules, along with sodium cations and water molecules. This formulation is considered a major mechanism of benefit of this molecule. This study was aimed to assess various brands of sacubitril/valsartan in the market for the presence of the cocrystal forms and compare them with Azmarda. a brand of sacubitril/valsartan manufactured by the innovator company. Methods: The study involved analysis of various marketed products containing sacubitril/valsartan tablets, including Azmarda. Both the Azmarda and marketed products were characterized using differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). Sodium content and dissolution studies were also performed . Results: A total of 16 brands of marketed products including Azmarda were studied. During DSC studies, unique melting pattern was observed in Azmarda, with exothermic peaks of sacubitril/valsartan detected at 140°C and 102°C, respectively. PXRD analysis revealed that none of the products exhibited the same crystal lattice as Azmarda. Azmarda, with a sodium level of 1.773%, was comparable to brand 2 (1.61%), brand 4 (1.73%), and brand 7 (1.58%). Azmarda demonstrated 64% release of sacubitril and 57% release of valsartan within 30 minutes in 0.1N HCl. Brand 7, brand 12, and brand 13 showed 52%, 57%, and 52% release of sacubitril, respectively, and 45%, 52%, and 48% release of valsartan, respectively, in 30 minutes. Conclusion: The absence of identical crystal lattice structures, highlights absence of cocrystalsin generic formulations. Such variations may impact the bioavailability and efficacy, emphasizing the importance of ensuring consistent and reliable therapeutic outcomes. [ABSTRACT FROM AUTHOR]

We begin by deriving the nonlinear Schrödinger equation (NLSE) in the presence of nonlinear microstructures, where the refractive index undergoes periodic modulation in the transverse direction for photonic crystal containing circular shape. Our investigation delves deeply into the intricate mechanisms behind transverse and longitudinal modulation of the refractive indexes, which aligns with the design of numerous manufactured slab microstructure waveguides. Theory of solitary waves in nonlinear microstructure, here unconventional fiber has been studied and examined in detail. In this work, composite methods leading both transverse and longitudinal modulation of refractive indexes have been presented in detail. The work also presents the diverse characteristics of this NLSE for both homogeneous and nonhomogeneous medium, encompassing various orders of nonlinearity specific to the nonlinear microstructure under consideration. Additionally, we analyze the wave propagation profiles for wide signals, which are wider than the periodicity of micro-structured photonic crystal. We also conduct a perturbation analysis for narrow signals that are even narrower than the periodicity of photonic crystal in transverse direction. [ABSTRACT FROM AUTHOR]

This study investigates the impact of kaolin and boehmite alumina binders on the synthesis, catalytic properties, and attrition resistance of a La0.7Sr0.3FeO3 (LSF) perovskite catalyst designed for the chemical looping partial oxidation (CLPO) of methane to produce synthesis gas sustainably. The as-synthesized and used catalysts with varying kaolin and boehmite alumina contents (KB(x,y)/LSF) were scrutinized by a variety of characterization methods, including XRD, FE-SEM/EDS, BET, TPD-NH3, and TPD-O2 techniques. The catalytic activity of the synthesized samples was tested at 800 to 900 °C in a fixed-bed reactor producing syngas through the CLPO process over the consecutive redox cycles. Additionally, the attrition resistance of the fresh and used catalyst samples was examined in a jet cup apparatus to assess their durability against the stresses induced by thermal shocks or changes in the crystal lattice caused by chemical reactions. The characterization results showed the pure perovskite crystal structure of KB(x,y)/LSF catalysts demonstrating adequate oxygen adsorption capacity, effective coke mitigation capability, robust thermal stability, and resilience to agglomeration during repetitive redox cycles. Among the tested catalysts, KB(25,15)/LSF was identified as the superior sample, as it could consistently produce syngas with a suitable H2:CO molar ratio varying from 2 to 3 within ten redox cycles at 900 °C, with CH4 conversion and CO selectivity values up to 64% and 87%, respectively. The synthesized catalysts demonstrated a logarithmic attrition pattern in the jet cup tests at room temperature, featuring high attrition resistance after the erosion of particle shape irregularities or weakly bound particles. Moreover, the KB(25,15)/LSF catalyst used at 900 °C showed great resistance in the attrition test, warranting its endurance in the face of extraordinarily harsh conditions in fluidized bed reactors employed for the CLPO process. [ABSTRACT FROM AUTHOR]

Quaternion and biquaternion symmetry transformations have been applied to non-Cartesian reference systems of direct and reciprocal crystal lattices. The transformations performed directly in the sets of crystal reference axes simplify the calculations, eliminate the need for orthogonalization, permit the use of crystallographic vectors for defining the directions of rotations and perform the computations directly in the crystal coordinates. The applications of the general quaternion transformations are envisioned for physical, chemical, crystallographic and engineering applications. The general quaternion multiplication rules for any symmetry-unrestricted lattices have been derived for the triclinic crystallographic system and have been applied to the biquaternion representations of all point-group symmetry elements, including the crystallographic hexagonal system. Cayley multiplication matrices for point-groups, based on the biquaternion symbols of proper and improper symmetry elements, have been exemplified. [ABSTRACT FROM AUTHOR]

Previous studies have demonstrated that the surface curvature of cylindrical magnetic nonawires can induce fascinating dynamic magnetization properties. It was recently proposed that ferromagnetic nanotubes can be utilized as skyrmion guides, enabling the avoidance of the annihilation of skyrmions in the lateral boundaries as in flat thin-film strips. In this work, we demonstrate via micromagnetic simulation that multiple skyrmions can be stabilized in a cross-section of a ferromagnetic nanotube with interfacial Dzyaloshinskii–Moriya interaction (iDMI). When uniformly arranged, these skyrmions together can perform as a crystal lattice for spin waves (SWs) propagating in the nanotube. Our simulations show that the skyrmion lattice can contribute a chiral effect to the SW passing through, namely a circular polarization of the SW. The handedness of the polarization is found to be determined by the polarity of the skyrmions. A physical explanation of the observed effect is provided based on the exchange of angular momentum between SWs and skyrmions during the scattering process. Our results display more possibilities to exploit magnetic nanotubes as SW and skyrmion guide in the development of novel spintronic devices. [ABSTRACT FROM AUTHOR]

Context: Ammonium Tutton salts have been widely studied in recent years due to their thermostructural properties, which make them promising compounds for application in thermochemical energy storage devices. In this work, a detailed experimental study of the Tutton salt with the formula (NH4)2Zn(SO4)2(H2O)6 is carried out. Its structural, vibrational, and thermal properties are analyzed and discussed. Powder X-ray diffraction (PXRD) studies confirm that the compound crystallizes in a structure of a Tutton salt, with monoclinic symmetry and P21/a space group. The Hirshfeld surface analysis results indicate that the main contacts stabilizing the material crystal lattice are H···O/O···H, H···H, and O···O. In addition, a typical behavior of an insulating material is confirmed based on the electronic bandgap calculated from the band structure and experimental absorption coefficient. The Raman and infrared spectra calculated using DFT are in a good agreement with the respective experimental spectroscopic results. Thermal analysis in the range from 300 to 773 K reveals one exothermic and several endothermic events that are investigated using PXRD measurements as a function of temperature. With increasing temperature, two new structural phases are identified, one of which is resolved using the Le Bail method. Our findings suggest that the salt (NH4)2Zn(SO4)2(H2O)6 is a promising thermochemical material suitable for the development of heat storage systems, due to its low dehydration temperature (≈ 330 K), high enthalpy of dehydration (122.43 kJ/mol of H2O), and hydration after 24 h. Methods: Computational studies using Hirshfeld surfaces and void analysis are conducted to identify and quantify the intermolecular contacts occurring in the crystal structure. Furthermore, geometry optimization calculations are performed based on density functional theory (DFT) using the PBE functional and norm-conserving pseudopotentials implemented in the Cambridge Serial Total Energy Package (CASTEP). The primitive unit cell optimization was conducted using the Broyden–Fletcher–Goldfarb–Shanno (BFGS) algorithm. The electronic properties of band structure and density of states, and vibrational modes of the optimized crystal lattice are calculated and analyzed. [ABSTRACT FROM AUTHOR]

The features of the infrared (IR) spectra of various isotopic forms of water (–OH, –OD, H2O, HDO, and D2O) included in the crystal structure of the main rock-forming minerals of lunar basalts—olivines (forsterite)—have been studied. The results of numerical modeling (CUSTEP/Biovia Materials Studio) and experimental studies using the FT-801 IR Fourier spectrometer with a plug-in using the method of disturbed internal reflection (Simex, Novosibirsk) are presented. Numerical calculations have shown that forsterite can contain hydroxyl groups –OH(D) in its crystal lattice under certain conditions. The possibility of retaining various isotopic forms of molecular water on the surface of forsterite has been experimentally verified and the corresponding IR spectra of the mineral with a water film have been obtained. The IR spectra of forsterite containing isotopologues of water obtained theoretically and experimentally are compared with the observations of the Chandrayaan-1 and SOFIA artificial lunar satellites. [ABSTRACT FROM AUTHOR]

Antimony-Selenium-Tin (Sb-Se-Sn) is a ternary chalcogenide have wide range of potential applications, because of their high strength, various crystal lattices, and electrical characteristics. In this work, the melt quenching method was used to synthesize the nanoparticles of Sb14Se86-xSnx (x = 0, 3, 6, 9, 12) chalcogenide glasses. X-ray diffraction (XRD) and the Scanning electron microscopy (SEM) of the Sb14Se74Sn12 chalcogenide glasses ascertained the amorphous characteristics. No extra impurity was detected in any chalcogenide, and the presence of only Sb, Se and Sn was detected from the EDS spectra. The decrease in band gap is revealed with the increase of Sn content in the Sb14Se86-xSnx glasses. Lowest band gap was observed in the Sb14Se74Sn12 chalcogenide, attributed to the large crystallite size. The FTIR spectrum of the sample reveals an absorption band roughly between 500 –400 cm-1, attributed to the vibrational modes for Sb–Se, Sn–Se and Sn-Sb bonds. In the chalcogenide glasses, the Sn and Sb 3d state comprises of two peaks, corresponding to doublet state (3d5/2 and 3d3/2), while as Se has only singlet state (3d). In conclusion, in the Sb14Se86-xSnx (x = 12) chalcogenide glass, an increase in photoluminescence intensity and the decrease in band gap makes it potential candiate for the infrared detectors, and the infrared optical fibres. [ABSTRACT FROM AUTHOR]

In this paper, 4. 2% ytterbium-doped calcium niobium gallium garnet (Yb∶Ca3 (NbGa)5 O12) crystals with diameter of 2 inch (1 inch =2. 54 cm) were grown by Bridgman method. The obtained crystals were intact and free of visible defects. Crystal structure was determine by XRD, which reveals that the crystal belongs to the cubic crystal system with lattice parameters a = b = c =12. 493 Å. The crystals were oriented and cut to obtain some (420) plane wafers with dimensions of 10 mm ×10 mm ×1 mm. These wafers were double-side polished to obtain the final samples. The performance of the samples was characterized through X-ray diffraction, ultraviolet-visible spectrophotometer, and fluorescence spectroscope. The results show that the rocking curve of the crystal has a full width at half maximum (FWHM) of 43″, and the transmittance reaches 80% in the near-infrared wavelength range. At 935 nm, FWHM of the absorption peak is 47. 15 nm and absorption crosssection is 1. 53 ×10 -20 cm2. When excited with a 980 nm laser, an emission peak was observed at 1 031 nm, corresponding to the transition of Yb3 + from the excited state 2 F5/2 to the ground state 2 F7/2. [ABSTRACT FROM AUTHOR]

Chiral perovskites are considered as promising candidates for circularly polarized luminescence (CPL) light source, by attracting the broader scientific community for their applications in chiral optoelectronics and spintronics. However, it is still a great challenge to achieve both substantial photoluminescence asymmetry (gCPL) and high photoluminescence quantum yield (PLQY) simultaneously for high CPL brightness due to the limitations associated with magnetic transition dipole moments. Herein, this problem is overcome and achieve both large gCPL of 1.6×10−2 and PLQY of 56% in chiral perovskite through the magnetic element doping strategy. The substitution of Pb2+ ion with smaller magnetic Mn2+ ions shrinks the crystal lattice around [MnBr6]4− octahedra, amplifying the asymmetric distortion surrounding the Mn2+ ions. Moreover, the transition associated with Mn2+ ions can harvest the photoexcitation energy in chiral perovskites, and its spin‐flipping characteristics enable highly efficient CPL from the d–d transition on Mn2+ energy levels. Furthermore, this magnetic element doping strategy is proven to be a universal tactic for enhancing CPL brightness as confirmed in a series of 1D‐ or 2D‐chiral perovskites with various chiral ligands or halogens. The findings provide an in‐depth understanding of the structure‐property relationship in chiral perovskites toward chiral optoelectronic and spintronic applications. [ABSTRACT FROM AUTHOR]

New Nd3+-doped cadmium molybdato-tungstates with the chemical formula of Cd1−3x▯xNd2x(MoO4)1−3x(WO4)3x (where x = 0.0283, 0.0455, 0.0839, 0.1430, 0.1875, 0.2000, 0.2500, and ▯ denotes a vacant site in the crystal lattice) were successfully synthesized by the high-temperature solid state reaction method, using CdMoO4 and Nd2(WO4)3 as the initial reactants. The structure and change in their lattice parameters as a function of Nd3+ ion concentration were investigated by the XRD (X-ray diffraction) method. The surface morphology and grain size of the doped materials were characterized by SEM (scanning electron microscopy). Their thermal properties and initial reactants were analyzed by DTA-TG (differential thermal analysis coupled with thermogravimetry) techniques. The optical properties of the Nd3+-doped cadmium molybdato-tungstates, such as optical band gap, were determined by UV–vis–NIR (ultraviolet–visible–near infrared) spectroscopy. The EPR (electron paramagnetic resonance) technique provided information on the type of magnetic interactions between Nd3+ ions. [ABSTRACT FROM AUTHOR]

A set of AgxCu1 – xGaSe2 (0 ≤ x ≤ 1) solid solution powders has been prepared by solid-state synthesis. Using a combination of X-ray diffraction analysis and Raman spectroscopy, it has been found that the samples have a single-phase tetragonal structure (space group I-42d). It has been shown that their crystal lattice parameters do not follow Vegard's law up to x ≈ 0.4. It has been revealed that the band gap of the samples also changes nonlinearly: initially it decreases and then increases. Studies of the low-temperature luminescence and microwave photoconductivity decay spectra have shown that a set of samples with x of 0 to ~0.4 and further in the region with x > 0.4 is characterized by an increase in the photogenerated current carrier lifetime in AgxCu1 – xGaSe2 powders. The observed effect is apparently attributed to the replacement of deep charge carrier traps, such as selenium vacancies, by shallower cation vacancies. [ABSTRACT FROM AUTHOR]

A medium‐grade, poorly weathered CO3‐type meteorite was subjected to artificial space weathering by 1 keV protons in three subsequent steps, with gradually increasing doses from 1011 to 1017 protons per cm2. The resulting mineral modifications were identified by Raman spectroscopy, with specific emphasis on main minerals such as olivine (bands: 817, 845 cm−1), pyroxene (1007 cm−1), and partly amorphous feldspar (509 cm−1), considering variation in band shift and bandwidth (full width at half maximum, FWHM). After the first and second irradiations, variable band position changes were observed, probably from metastable alterations by Mg loss of the minerals, while the third stronger irradiation showed band shift dominated by amorphization. The olivine and pyroxene show weak increase in FWHM after the first irradiation, while more changes happened after the second and third irradiations. The flux after the third irradiation was higher than in other works, caused stronger damage in crystal lattice, partly resembling to dimerization as described by shock metamorphism. The glassy feldspar was characterized by high FWHM values already at the beginning, indicating weak crystallinity already that become even less crystallized, thus their bands disappeared after the third irradiation. Bands of hydrous minerals (goethite clay, chlorite) were not visible after the third irradiation, confirming some earlier results in the literature. Based on our results, moderately fresh surfaces could show stochastic but small spectral differences compared to the fresh most meteorites by metastable mineral alterations. The interpretation of Raman spectra of heavily space‐weathered surfaces could further benefit from the joint evaluation of alteration induced by both shock impact alteration and space weathering. [ABSTRACT FROM AUTHOR]

The electronic properties of moiré heterostructures depend sensitively on the relative orientation between layers of the stack. For example, near-magic-angle twisted bilayer graphene (TBG) commonly shows superconductivity, yet a TBG sample with one of the graphene layers rotationally aligned to a hexagonal Boron Nitride (hBN) cladding layer provided experimental observation of orbital ferromagnetism. To create samples with aligned graphene/hBN, researchers often align edges of exfoliated flakes that appear straight in optical micrographs. However, graphene or hBN can cleave along either zig-zag or armchair lattice directions, introducing a 30° ambiguity in the relative orientation of two flakes. By characterizing the crystal lattice orientation of exfoliated flakes prior to stacking using Raman and second-harmonic generation for graphene and hBN, respectively, we unambiguously align monolayer graphene to hBN at a near-0°, not 30°, relative twist angle. We confirm this alignment by torsional force microscopy of the graphene/hBN moiré on an open-face stack, and then by cryogenic transport measurements, after full encapsulation with a second, nonaligned hBN layer. This work demonstrates a key step toward systematically exploring the effects of the relative twist angle between dissimilar materials within moiré heterostructures. [ABSTRACT FROM AUTHOR]

Mesocrystals are ordered nanoparticle superstructures, often with internal porosity, which receive much recent research interest in catalysis, energy storage, sensors, and biomedicine area. Understanding the mechanism of synthetic routes is essential for precise control of size and structure that affect the function of mesocrystals. The classical synthetic strategy of mesocrystal was formed via self-assembly of nanoparticles with a faceted inorganic core but a denser (or thicker) shell of organic molecules. However, the potential materials and synthetic handles still need to be explored to meet new applications. In this work, we develop a non-classical synthetic strategy for organic molecules, such as tetrakis (4-hydroxyphenyl) ethylene (TPE-4OH), tetrakis (4-bromophenyl) ethylene (TPE-4Br), and benzopinacole, to produce mesocrystals with composed of microrod arrays via co-solvent-induced crystal transformation. The aligned nanorods are grown epitaxially onto organic microplates, directed by small lattice mismatch between plates and rods. Thus, the present work offers general synthetic handle for establishing well-organized organic mesocrystals. [ABSTRACT FROM AUTHOR]

A nonlocal phase-field crystal (NPFC) model is presented as a nonlocal counterpart of the local phase-field crystal (LPFC) model and a special case of the structural PFC (XPFC) derived from classical field theory for crystal growth and phase transition. The NPFC incorporates a finite range of spatial nonlocal interactions that can account for both repulsive and attractive effects. The specific form is data-driven and determined by a fitting to the materials structure factor, which can be much more accurate than the LPFC and previously proposed fractional variant. In particular, it is able to match the experimental data of the structure factor up to the second peak, an achievement not possible with other PFC variants studied in the literature. Both LPFC and fractional PFC (FPFC) are also shown to be distinct scaling limits of the NPFC, which reflects the generality. The advantage of NPFC in retaining material properties suggests that it may be more suitable for characterizing liquid–solid transition systems. Moreover, we study numerical discretizations using Fourier spectral methods, which are shown to be convergent and asymptotically compatible, making them robust numerical discretizations across different parameter ranges. Numerical experiments are given in the two-dimensional case to demonstrate the effectiveness of the NPFC in simulating crystal structures and grain boundaries. [ABSTRACT FROM AUTHOR]

The performance and stability of organic metal halide perovskite (OMHP) optoelectronic devices have been associated with ion migration. Understanding of nanoscale resolved organic cation migration mechanism would facilitate structure engineering and commercialization of OMHP. Here, we report a three‐dimensional approach for in situ nanoscale infrared imaging of organic ion migration behavior in OMHPs, enabling to distinguish migrations along grain boundary and in crystal lattice. Our results reveal that organic cation migration along OMHP film surface and grain boundaries (GBs) occurs at lower biases than in crystal lattice. We visualize the transition of organic cation migration channels from GBs to volume upon increasing electric field. The temporal resolved results demonstrate the fast MA+ migration kinetics at GBs, which is comparable to diffusivity of halide ions. Our findings help understand the role of organic cations in the performance of OMHP devices, and the proposed approach holds broad applicability for revealing migration mechanisms of organic ions in OMHPs based optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this study, we investigated the influence of the position and quantitative content of scandium in YSAG:Cr on the efficiency of chromium cation valence conversion. YSAG:Cr ceramic powders were synthesized using the chemical precipitation method. It was determined that the microstructure of ceramics and the luminescent properties of YSAG:Cr4+ depend on the predominant position of scandium, whether it replaces octahedral or dodecahedral positions in the garnet crystal lattice. An increase in Sc dod content contributed to a decrease in grain size and a shift of the emission peak of Cr4+ ions towards the short-wavelength region. Conversely, an increase in Sc oct content led to an increase in grain size and a shift of the maximum of the luminescent band towards the long-wavelength region. It was found that increasing the quantitative content of scandium in the octahedral position in the garnet structure by up to 50 % enhances the efficiency of the conversion of Cr3+ to Cr4+, while an increase in the proportion of Sc dod resulted in a decrease in conversion efficiency. [ABSTRACT FROM AUTHOR]

Optical ceramics with 50 at.% Sc in both dodecahedral ({Y 1·17 Er 0.03 Yb 0.3 Sc 1.5 }[Al 1.8 Sc 0.2 ]Al 3 O 12 , {Y 1.2 Yb 0.3 Sc 1.5 }[Al 1.8 Sc 0.2 ]Al 3 O 12) and octahedral ({Y 2·52 Er 0.03 Yb 0.3 Sc 0.15 }[Al 1.0 Sc 1.0 ]Al 3 O 12 , {Y 2.55 Yb 0.3 Sc 0.15 }[Al 1.0 Sc 1.0 ]Al 3 O 12) sites of the garnet structure were synthesized using the non-reactive vacuum sintering method. Analysis of the phase composition, thermal diffusivity, transmission in the visible and IR regions of the spectrum, as well as luminescent properties (Stokes and anti-Stokes luminescence, luminescence decay kinetics) revealed clear correlations with the chemical composition of ceramics. It has been determined that solid solutions in which Y3+ cations are partially replaced by Sc3+ cations, compared to solid solutions in which Al3+ cations in the octahedral site are partially replaced by Sc3+, are characterized by lower crystal lattice parameters (11.883 ± 0.004 Å and 12.153 ± 0.005 Å); lower thermal conductivity values (4.72 W/(m·K) and 5.9 W/(m·K)); higher characteristic vibration frequencies of structural groups; shorter lifetimes of excited states of Yb3+ (1.41 μs and 1.56 μs for YSAG:Yb; 0.42 μs and 0.65 μs for YSAG:Yb,Er) and Er3+ (8.6 μs and 9.2 μs) cations; higher efficiency of energy transfer from Yb3+ to Er3+. The results clearly indicate that solid solutions with high concentrations of Sc3+ cations in the dodecahedral site can also be effective matrices for Yb3+ and Er3+ cations compared to solid solutions with a predominant introduction of scandium in the octahedral site. [ABSTRACT FROM AUTHOR]

Zirconia dental ceramics have evolved from uniform blocks of 3 mol.% yttria (3Y) to strength- and color-graded blocks containing 3 mol.% and 5 mol.% components. Relatively little is known about the graded materials' compositions and microstructures. Concerns have been raised about aging and degradation. This study investigated the microstructure, elemental composition, and phase content of different zones of strength- and color-graded zirconia blocks using scanning electron microscopy, x-ray fluorescence, and x-ray diffraction. Specimens were made from green-state blocks using CAD/CAM machining and sintering. Two strength- and color-graded zirconia materials had different grain sizes, elemental compositions, and phase contents between their top and bottom zones, these data being internally consistent as well as being broadly consistent with prior compositional physical property data. A color-graded zirconia material did not exhibit substantial differences between its top and bottom zones, consistent with expectations and previously published data. Modeling phase content for complex yttria-doped zirconia crystal systems with multiple heterogeneous crystal lattices from XRD data was inherently difficult, which may account for the ranges among previously published data; authors should describe detailed methodologies. Detailed compositional data at the scale of the microstructure is needed to relate composition to phase content, physical behavior, including crack evolution. [ABSTRACT FROM AUTHOR]

In this work, composites made of polylactide (PLA) and filled with alkali-pretreated rice husk (RH) were investigated. Composites containing 20, 30, and 40 wt.% of RH were synthesized. It was shown that alkaline treatment, along with the change in crystal lattice, led to an increase in the content of non-crystalline parts and the volume of intercrystalline spaces, and the internal surface of the cellulose fiber increased, which resulted in improved adhesion of the fiber with the matrix. The addition of rice husk to the PLA matrix led to an increase in the flexural modulus, which increased to 2881 MPa for the PLA/RH (80/20 wt.%) and 3034 MPa for the PLA/RH (70/30 wt.%) composites and lowered the peak load stress by approximately 43% for the composite with 20 wt.% RH and 56% for the composite with 30 wt.% RH. The reduction in the degree of PLA crystallinity allows macromolecules to move more freely in amorphous regions, which has a positive effect on increasing the flexibility of materials in general. The optimal formulation is a composite consisting of 30% RH and 70% PLA matrix. [ABSTRACT FROM AUTHOR]

A series of triphenylamine‐quinoxaline donor‐acceptor (bipolar) compounds (TPA‐QH, TPA‐QMe, TPA‐QCOOH and TPA‐QNO2) with different substituents were synthesized and investigated their fluorescence properties, including stimuli‐induced fluorescence responses in solution and the solid‐state. Single crystal structural analysis revealed non‐planar molecular conformation, substituent controlled intermolecular interactions and molecular packing in the crystal lattice. TPA‐QH, TPA‐QMe, TPA‐QCOOH and TPA‐QNO2 showed tunable solid‐state emission from green to red. TPA‐QH showed strong fluorescence at 487 nm (quantum yield (Φf)=28.3 %) whereas NO2 substituted TPA‐QNO2 exhibited relatively weak fluorescence at 610 nm (Φf=4.3 %). Density functional theoretical (DFT) calculations also indicated reduction of optical bandgap with substituting electron withdrawing group. The donor‐acceptor structure with intramolecular charge transfer (ICT) resulted solvent polarity dependent fluorescence tuning. The presence of acid responsive quinoxaline group was utilized to demonstrate pH‐responsive fluorescence switching and dual state fluorescence was utilized for fabricating rewritable fluorescent platform. Thus, the present study provides a structural insight to develop dual state emissive triphenylamine–quinoxaline based bipolar materials for optoelectronic applications. [ABSTRACT FROM AUTHOR]

Complex hydrides, such as sodium borohydride (NaBH4), are attractive materials for hydrogen storage because of their high hydrogen capacity. However, practical application of these materials is limited because of their unfavorable hydrogen thermodynamics and poor kinetics. Herein, it is demonstrated that the inclusion of BF4− in NaBH4 results in remarkable Na+ conductivity of 1.5 × 10−3 S cm−1, which is 10 000 times higher compared to pure NaBH4 (7.0 × 10−8 S cm−1) at 115 °C. The ionic conductivity is also comparable to values reported for some of the best borohydride‐based conductors reported to date. More remarkably, this improvement of ionic conductivity is found to be correlated to lower hydrogen release temperatures for BF4−‐modified NaBH4 releasing hydrogen at a temperature of 200 °C instead of 510 °C in the case of pristine NaBH4. Nudged elastic band calculations based on density functional theory reveal that partial substitution of the [BH4]− groups in NaBH4 by BF4− may lead to the formation of distortions within the NaBH4 crystal lattice with favorable channels for Na+ mobility enabling the release of hydrogen at low temperatures. [ABSTRACT FROM AUTHOR]

The lattice mismatch between γ-CuI and Al2O3 (sapphire) is as large as 27.1% due to differences in crystal systems and lattice constants. To achieve epitaxial growth on the initial surface of the substrate, lattice mismatch can be minimized through domain matching. In this work, the γ-CuI film was epitaxially grown on the Al2O3(001) substrate by employing the physical vapor transport technology. The morphology, structure, and rotation domain matching of the films were investigated via SEM, XRD, electron backscatter diffraction, and STEM/TEM. The results revealed that the film grew preferentially along the (111) plane, and the full width at half maximum of the (111) diffraction peak in the rocking curve was 0.45°, which indicated the high degree of crystallinity of the film. The surface of the γ-CuI film exhibited two kinds of triangular crystal domains with a relative rotation angle of ∼60°. The interior of the crystal domains possessed a step-like structure. The two types of triangular crystal domains in the film were attributed to different rotation domains, and the interface was ascribed to the ⟨111⟩ 60° twin boundaries. The epitaxial matching mode was found to be CuI ⟨11 2 ̄ ⟩ (111)//Al2O3 [ 1 ̄ 1 ̄ 0] (001), resulting in ∼4.6% lattice mismatch between γ-CuI and Al2O3 along the Al2O3 ⟨ 1 ̄ 10 ⟩ direction, which is significantly lower than previously reported data. [ABSTRACT FROM AUTHOR]

The microstructure, phase composition and elemental composition in the α- and β-phases of the two-phase wrought Ti-5.7Al-1.6V-3Mo titanium alloy at room temperature were studied by transmission electron microscopy and X-ray energy-dispersive spectroscopy. The temperature ranges of phase transformations in the alloy during heating from 298 to 1523 K were studied by differential scanning calorimetry (DSC). Two endothermic peaks were observed on the DSC curve at the temperatures of 1078 K and 1207 K, and one exothermic peak was observed at a temperature of 1123 K. The endothermic peak on the DSC curve at a temperature of 1078 K is due to the formation of α″-martensite, at a temperature of 1207 K is caused by α → β phase transformation. The exothermic peak at a temperature of 1123 K, presumably, corresponds to the polymorphic transformation of brookite → rutile in TiO2 oxide. High-temperature synchrotron studies were carried out from room temperature to 1373 K. It was found that the increase in lattice parameters during heating is nonlinear. Possible mechanisms of the nonlinear change in the lattice parameters at temperatures above 1200 K are discussed. At T > 1000 K α″-martensite was formed by β → α″ phase transformation. An increase in the volume fraction of α″-phase with increase in temperature was accompanied by a decrease in the volume fraction of β-phase. An increase in microstrain of the α-phase lattice and a decrease in microstrain of the β-phase lattice were observed upon heating. [ABSTRACT FROM AUTHOR]

The use of tris(4-aminophenyl)amine (TAPA) as central to the synthesis of both polyimines and polyimides and covalent organic frameworks and inorganic cages, among others, has grown in the last few years. The resulting materials exhibit high performance in their area of application. In this contribution, the crystal structures of two TAPA derivatives, triethyl (nitrilotris(benzene-4,1-diyl))tricarbamate (1) and triethyl 2,2′,2″-((nitrilotris(benzene-4,1-diyl))tris(azanediyl))tris(2-oxoacetate) (2), are described. The molecular and supramolecular structures of both compounds were compared between them and with analogous compounds. The analyses of their vibrational and 13C-CPMAS NMR spectroscopies, as well as their thermal stability, were included and corelated with the crystal structure. Hirshfeld surface analysis on the crystal structures of both TAPA derivatives revealed the stabilization of the crystal network via the amide N—H∙∙∙O interactions of dispersive nature in the carbamate, whereas dispersive carbonyl–carbonyl interactions also played a competitive role in the supramolecular arrangement of the oxamate. Interaction energy DFT calculations performed at the B3LYP/6-31G(d,p) level allowed us to estimate the energy contributions and nature of several interactions in terms of the stability of both crystal lattices. [ABSTRACT FROM AUTHOR]

Guanidine-containing molecules are an interesting class of compounds within both medicinal and material sciences. Having knowledge of their tautomerism is key in designing guanidines that interact with biological and chemical receptors. However, there are limited data on the solid-phase structure of N,N′-substituted guanidines. Thus, eleven guanidines bearing a 4,6-dimethylpyrimidyl at one end and substituents of varying sizes and electronic properties at the other side, were synthesised, crystallised, and analysed by X-ray crystallography. Calculations of isolated molecules of tautomer energies and bond lengths were performed for comparison. One class of guanidines crystallised as a cis–trans tautomer with the shorter bond directed towards the pyrimidyl unit. When more electron-deficient aniline substituents were inserted, the crystallised tautomer changed to a cis–cis form where the shorter bond was directed towards the aniline. The switch in the tautomer structure is concluded to be due to both the electronic properties of the substituents and the intermolecular hydrogen bonding in the crystal lattice. [ABSTRACT FROM AUTHOR]

This work aims to present the building blocks for an all direct laser written integrated spectrometer in the mid-infrared (3.39–4.1 μm range) based on the SWIFTS (Stationary Wave Integrated Fourier Transform Spectrometer) principle. In a SWIFTS-Gabor configuration, the light from the source interferes with itself in the middle of a channel waveguide, creating a stationary wave. This interferogram is then sampled through scattering centers placed on top of the waveguide that radiate the light they extract onto a detector placed directly on the sample. Finally, the spectrum of the source is retrieved through a Fourier transform. To implement a SWIFTS, two main photonic functions are required: the waveguide and the scattering centers. In this work, both functions have been created using Direct Laser Writing (DLW), a versatile technique, allowing to easily access 3D configurations and to reduce fabrication time. DLW focuses a femtosecond laser onto a sample so as to locally change the crystal lattice, resulting in its structural modification. The waveguides presented here are surface half-circular cladding structures made through type II modifications in the sample, and the scattering centers are surface damage tracks (also referred to as grooves). These surface tracks are creating dielectric discontinuities in the evanescent part of the stationary wave, resulting in the light being radiated outside the waveguide. All of these are made in a z-cut lithium niobate substrate for future implementation of the electro-optic effect. We demonstrate that we have functional waveguides in the mid-IR and that our grooves are extracting the stationary wave as expected, showing promising results for future implementation of a complete mid-IR SWIFTS using DLW. [ABSTRACT FROM AUTHOR]

Lithium cobalt oxide is a convenient model material for the vast family of cathode materials with a layered structure and still retains some commercial perspectives for microbatteries and some other applications. In this work, we have used ab initio calculations, x-ray diffraction, Raman spectroscopy, and a theoretical physical model, based on quasi-harmonic approximation with anharmonic contributions of the three-phonon and four-phonon processes, to study a temperature-induced change of Raman spectra for LiCoO2. The obtained values of shift and broadening for Eg and A1g bands can be used for quantitative characterization of temperature change, for example, due to laser-induced heating during Raman spectra measurements. The theoretical analysis of the experimental results lets us conclude that Raman spectra changes for LiCoO2 can be explained by the combination of thermal expansion of the crystal lattice and phonon damping by anharmonic coupling with comparable contributions of the three-phonon and four-phonon processes. The obtained results can be further used to develop Raman-based quality control tools. [ABSTRACT FROM AUTHOR]

An estimation of category of liquid crystalline (LC) phase based on composite lattices using linear algebra and lattice parameters is proposed. The vector space in three dimensions (3 D) is dissolved in the initial phase into two dimensions (2 D) , and one dimension (1 D) subspace in a 3D crystal, respectively, rotate and/or slide between each other during thermal process. In linear algebra, this state is designated as [ 2 D ⊕ 1 D ] composite subspaces of vector. As per linear algebraic approach, [ 2 D ⊕ 1 D ] is not identical with 3D, and the mathematical sign ⊕ indicates addition directly. The phase is represented as [ 2 D ⊕ 1 D ] lattice-based composite phase. Apart from the [ 2 D ⊕ 1 D ] phase, two more mixed phases with [ 1 D ⊕ 1 D ] and [ 1 D ⊕ 1 D ⊕ 1 D ] may also be theoretically studied using linear algebra. Finally, the category of phase is proposed to be analyzed with link to its transition temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] The serious combination of abundant electrons/holes in bulk primarily hinders the efficiency in the photocatalytic reaction. It is crucial to control the spatial charge dynamics through delicately designing the crystal configuration of photocatalyst. In this work, a modified tungsten trioxide nanosheet colloid (M-WO 3) was synthesized by an ion exchange method. Compared to pristine WO 3 (P-WO 3), the crystal lattice vibration frequency of M-WO 3 increases from 2.8 meV to 4.3 meV, which effectively prohibits electron–phonon coupling and powerfully accelerates the separation and transfer of photoinduced charge carriers. Irradiated by visible-light, M-WO 3 shows much higher photocatalytic bacterial inactivation performance than P-WO 3. In addition, this regulation method increases the surface charges of the WO 3 colloid to improve its stability, which endows this colloid photocatalyst with broad prospects in practical photocatalytic antibacterial applications. This work offers guidance to construct efficiently separated photoinduced electron/hole pairs of the colloid photocatalyst by designing its crystal structure. [ABSTRACT FROM AUTHOR]

Since 2000, corundum heat-treated by beryllium (Be) has been successfully experimented to lighten the over-dark blue basaltic-related sapphire. In early 2006, advancements in heat treatment techniques in Chanthaburi revealed the ability to darken metamorphic-related blue sapphires using Be treatment, contrary to the previous lightening effect. The role of Be in corundum coloration obviously remains not well understood. Therefore, an experiment involving heat treatment was conducted to study changes in terms of physical, chemical, gemological, and spectroscopic properties of the blue sapphire after beryllium heat treatment, which has never been done before. Natural sapphires from Sri Lanka, varying in color and transparency, were subjected to Be heat treatment across a range of temperatures and in different types of furnaces (e.g. LPG gas, electric, and fuel oil), under both oxidizing and reducing atmospheres. The samples were studied after each heating step for gemological and spectroscopic properties using UV-Vis-NIR and infrared spectroscopy, as well as chemical composition using LA-ICP-MS. The combination of color appearance, absorption spectra, and chemical data suggests the role of beryllium in sapphire coloration. Be-trapped hole yellow color centers formed during oxidation heating can be deactivated through reduction heating. The resulting color is determined by the Mg to Ti ratio, with no influence from Be. However, most beryllium-treated blue sapphires had an Mg/Ti ratio greater than 1. The presence of higher energy level elements, such as Si, may facilitate the formation of blue color by allowing remaining titanium to pair with iron. Therefore, the blue coloration is mainly caused by strong broad absorption bands of Fe2+/Ti4+ IVCT mechanism without Fe2+/Fe3+ IVCT. The study highlights the complex interplay of elements within the crystal lattice and contributes to our understanding of color development mechanisms in beryllium-treated sapphires. [ABSTRACT FROM AUTHOR]

Here we review scanning tunneling microscopy research on the surface determination for various types of kagome materials, including 11-type (CoSn, FeSn, FeGe), 32-type (Fe3Sn2), 13-type (Mn3Sn), 135-type (AV3Sb5, A = K, Rb, Cs), 166-type (TbMn6Sn6, YMn6Sn6 and ScV6Sn6), and 322-type (Co3Sn2S2 and Ni3In2Se2). We first demonstrate that the measured step height between different surfaces typically deviates from the expected value of ±0.4 ∼0.8Å, which is owing to the tunneling convolution effect with electronic states and becomes a serious issue for Co3Sn2S2 where the expected Sn-S interlayer distance is 0.6Å. Hence, we put forward a general methodology for surface determination as atomic step geometry imaging, which is fundamental but also experimentally challenging to locate the step and to image with atomic precision. We discuss how this method can be used to resolve the surface termination puzzle in Co3Sn2S2. This method provides a natural explanation for the existence of adatoms and vacancies, and beyond using unknown impurity states, we propose and use designer layer-selective substitutional chemical markers to confirm the validity of this method. Finally, we apply this method to determine the surface of a new kagome material Ni3In2Se2, as a cousin of Co3Sn2S2, and we image the underlying kagome geometry on the determined Se surface above the kagome layer, which directly visualizes the p-d hybridization physics. We emphasize that this general method does not rely on theory, but the determined surface identity can provide guidelines for first-principles calculations with adjustable parameters on the surface-dependent local density of states and quasi-particle interference patterns. [ABSTRACT FROM AUTHOR]

Out‐of‐plane polarization is a highly desired property of two‐dimensional (2D) ferroelectrics for application in vertical sandwich‐type photoferroelectric devices, especially in ultrathin ferroelectronic devices. Nevertheless, despite great advances that have been made in recent years, out‐of‐plane polarization remains unrealized in the 2D hybrid double perovskite ferroelectric family. Here, from our previous work 2D hybrid double perovskite HQERN ((S3HQ)4EuRb(NO3)8, S3HQ=S‐3‐hydroxylquinuclidinium), we designed a molecular strategy of F‐substitution on organic component to successfully obtain FQERN ((S3FQ)4EuRb(NO3)8, S3FQ=S‐3‐fluoroquinuclidinium) showing circularly polarized luminescence (CPL) response. Remarkably, compared to the monopolar axis ferroelectric HQERN, FQERN not only shows multiferroicity with the coexistence of multipolar axis ferroelectricity and ferroelasticity but also realizes out‐of‐plane ferroelectric polarization and a dramatic enhancement of Curie temperature of 94 K. This is mainly due to the introduction of F‐substituted organic cations, which leads to a change in orientation and a reduction in crystal lattice void occupancy. Our study demonstrates that F‐substitution is an efficient strategy to realize and optimize ferroelectric functional characteristics, giving more possibility of 2D ferroelectric materials for applications in micro‐nano optoelectronic devices. [ABSTRACT FROM AUTHOR]

Changes in the phase composition of serpentinite from the Zhitikarinsky deposit (Kazakhstan) were studied during heat treatment in the temperature range of 105–800 °C in order to determine the phase that leads to an increase in the reactivity of serpentinite during interactions with acids. In accordance with this, the task was set to consider the influence of temperatures (105 °C, 600 °C, 660 °C, 725 °C, 750 °C and 800 °C), selected according to the extreme points of the main transformations from its derivatogram, on changes in the phase composition. The effects of heat treatment on the phase composition and reactivity of serpentinite during interactions with sulfuric acid were studied and discussed using the diffraction patterns of serpentinite heat treated at selected temperatures for 1 h and using methods of thermodynamic evaluation of the possible reactions in the temperature range of 350–750 °C, as well as establishing the nature of their interaction with sulfuric acid under identical conditions. It has been shown that, in the range of 600–750 °C, the crystal lattice of the structural composition of serpentinite is completely destroyed with the formation of not only magnesium silicates but possibly also magnesium oxide, which leads to the thermal activation of serpentinite in relation to interactions with acids and the improvement of the technological process of extracting magnesium from it. The greatest increase in reactivity was found in serpentinite samples heat treated at temperatures of 725 °C and 750 °C, which can be recommended for the thermal activation of serpentinite before using acid methods to improve the technological performance of the process of extracting magnesium from serpentinite. [ABSTRACT FROM AUTHOR]

The equimolar reaction between 1,9-bis(N,N-dimethylaminomethyl)-5,5′-diphenyldipyrromethane, H2L1 or 1,9-bis(3,5-dimethylpyrazolylmethyl)-5,5′-diethyldipyrromethane, H2L2 and [NiCl2(DME)] in the presence of KH yielded the neutral mononuclear nickel(II) complexes [Ni(L1)-κ4N,N,N,N], 1 and [Ni(L2)-κ4N,N,N,N], 2, respectively. Their X-ray structures revealed the formation of triple chelation by the ligand in both structures with quite different nickel(II)-surrounded square planar geometries owing to the steric difference between –NMe2 and 3,5-dimethylpyrazolyl groups. While the –NMe2 group substituted ligand L1 afforded nickel complex 1 with a plane of symmetry, 3,5-dimethylpyrazole substituted L2 rendered helical chirality in the structure of complex 2. Both the enantiomers (Δ and Λ) of complex 2 were observed in the crystal lattice. Their solution state behaviors were consistent with the solid-state structures as monitored by 1H NMR spectroscopy. Both the enantiomers of complex 2 were present in a dynamic equilibrium in solution and studied by variable temperature 1H NMR spectroscopy. Similar to the chiral complex, the corresponding ligand H2L2 also exhibited chirality as shown by its crystal structure and the two ligand enantiomers participated in a very fast dynamic interconversion, which became slower upon metalation. [ABSTRACT FROM AUTHOR]

NASICON-structured Li 1.3 Al 0.3 Ti 1.7 (PO 4) 3 (LATP) solid electrolyte has low grain boundary conductivity, which impedes its practical application. Herein, W was adopted to partially replace the Al element in LATP to improve its grain boundary conductivity. The W doping reduces the crystal lattice of the electrolyte, which is detrimental to the grain conductivity. But the doping of W can make the grains closely connect and reduce the voids between the grains, which can greatly enhance the grain boundary conductivity. The LATP sample with the W doping content of 0.03 (LATWP003) exhibits the highest total ionic conductivity of 1.186 mS/cm at 30 ℃, which results from the optimum grain boundary conductivity of 2.315 mS/cm. Moreover, the LATWP003 electrolyte displays a negligible electronic conductivity of 2.01×10−9 S/cm. The LiFePO 4 /LATWP003/Li battery with PVDF-HFP polymer protective layer can be charged and discharged. Therefore, the W doped LATP sample is a promising electrolyte for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

The internal modification with rare earth ion doping proved to be a very effective strategy for improving the luminescent properties of NaYF 4 -based upconversion materials. However, greatly enhancing the luminescence efficiency of NaYF 4 :Yb3+/Er3+ remains a major challenge. Herein, the effects of Sn4+ doping on the structure and luminescent performance of such material were explored. The hydrothermal molten-salt method was applied to synthesize the Sn4+-doped NaYF 4 :Yb3+/Er3+ upconversion materials, and their crystal structures, morphologies, surface chemical composition and element states, and luminescence performance were characterized. It was found that Sn4+ doping can significantly enhance the luminescence intensity and tailor the chromaticity of NaYF 4 :Yb3+/Er3+. In particular, the green (G) and red (R) luminescence intensity levels of the 30 mol% Sn4+ doped material were increased by factors of 26.97 and 38.91, respectively. The R/G ratio was incremented from 0.34 for the undoped material to 0.83 for the 40 mol% Sn4+ doped counterpart. The Sn4+ doping led to the change of lattice distortion and crystal growth pattern of NaYF 4 :Yb3+/Er3+. The mechanism for Sn4+ doping to affect the luminescence properties of the prepared upconversion material was also explored. The changes in luminescence intensity levels and R/G ratios could be attributed to the highly asymmetric distorted lattice and crystal field resulting from Sn4+ doping. [ABSTRACT FROM AUTHOR]

The kinetics of phase transformations in the nitriding process α-Fe → γ'-Fe4N → ε-Fe3-2N of the pre-reduced iron ammonia synthesis catalyst was investigated under in situ conditions (atmospheric pressure, 350 °C) by measuring changes of mass, gas phase composition, and magnetic permeability in a differential tubular reactor. The iron nanocrystallite size distribution according to their specific active surface areas was measured, and it was found that the catalyst is bimodal as the sum of two Gaussian distributions, also differing in the value of the relative magnetic permeability. Relative magnetic permeability of small α-Fe crystals in relation to large crystals is higher by 0.02. In the area of α → γ' transformation, the magnetic permeability dependencies change, proving the existence of two mechanisms of the α-Fe structure change in the α-Fe → γ'-Fe4N transformation. In the first area, a solution of α-Fe (N) is formed with a continuous and insignificant change of the crystal lattice parameters of the iron lattice. In the second area, there is a step, oscillatory change in the parameters of the iron crystal lattice in FexN (x = 0.15, 0.20, 0.25 mol/mol). In the range of γ'-Fe4N → ε-Fe3-2N transformation, a solution is formed, with nitrogen concentration varying from 0.25–0.45 mol/mol. During the final stage of the nitriding process, at a constant value of the relative magnetic permeability, only the concentration of nitrogen in the solution εr increases. The rate of the phenomenon studied is limited by a diffusion rate through the top layer of atoms on the surface of iron nanocrystallite. The estimated value of the nitrogen diffusion coefficient varied exponentially with the degree of nitriding. In the area of the solution, the diffusion coefficient is approximately constant and amounts to 5 nm2/s. In the area of oscillatory changes, the average diffusion coefficient changes in the range of 3–11 nm2/s, and is inversely proportional to the nitrogen content degree. The advantage of the research method proposed in this paper is the possibility of simultaneously recording, under reaction conditions, changes in the values of several process parameters necessary to describe the process. The research results obtained in this way can be used to develop such fields of knowledge as heterogeneous catalysis, materials engineering, sensorics, etc. [ABSTRACT FROM AUTHOR]

In this investigation, an effort was made to introduce Ag into the CeO2 fluorite crystal lattice to form Ce0.99Ag0.01O2-δ (ACRM) using an ammonium hydroxide-assisted co-precipitation method. The resulting powder obtained after the co-precipitation reaction, filtration, and drying was annealed at 800 °C in a muffle furnace to obtain crystalline ACRM. The phase composition and microstructure of the synthesized ACRM were analyzed using a powder X-ray diffractometer (PXRD) and a scanning electron microscope (SEM). The characterized ACRM powder was then subjected to multiple thermochemical thermal reduction (TR) and CO2 splitting (CDS) cycles using a high-temperature thermogravimetric analyzer (TGA). The TR step was conducted using Ar gas as an inert atmosphere, maintaining the temperature at 1400 °C for 60 min. Subsequently, the same powder was subjected to the CDS step by treating it with a gaseous mixture of 50% CO2 and Ar gas at 1000 °C for 30 min. ACRM displayed stable redox reactivity towards thermochemical CDS cycles by generating an average of 50.9 μmol of O2/g·cycle and 101.6 μmol of CO/g·cycle, respectively, over 10 thermochemical cycles. [ABSTRACT FROM AUTHOR]