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An approach is presented for simulating multipulse nuclear magnetic resonance (NMR) spectra of polycrystalline solids directly in the frequency domain. The approach integrates the symmetry pathway concept for multipulse NMR with efficient algorithms for calculating spinning sideband amplitudes and performing interpolated finite-element numerical integration over all crystallite orientations in a polycrystalline sample. The numerical efficiency is achieved through a set of assumptions used to approximate the evolution of a sparse density matrix through a pulse sequence as a set of individual transition pathway signals. The utility of this approach for simulating the spectra of complex materials, such as glasses and other structurally disordered materials, is demonstrated. [ABSTRACT FROM AUTHOR]

Reduced order models (ROMs) are often coupled with concurrent multiscale simulations to mitigate the computational cost of nonlinear computational homogenization methods. Construction (or training) of ROMs typically requires evaluation of a series of linear or nonlinear equilibrium problems, which itself could be a computationally very expensive process. In the eigenstrain‐based reduced order homogenization method (EHM), a series of linear elastic microscale equilibrium problems are solved to compute the localization and interaction tensors that are in turn used in the evaluation of the reduced order multiscale system. These microscale equilibrium problems are typically solved using either the finite element method or semi‐analytical methods. In the present study, a reduced order variational spectral method is developed for efficient computation of the localization and interaction tensors. The proposed method leads to a small stiffness matrix that scales with the order of the reduced basis rather than the number of degrees of freedom in the finite element mesh. The reduced order variational spectral method maintains high accuracy in the computed response fields. A speedup higher than an order of magnitude can be achieved compared to the finite element method in polycrystalline microstructures. The accuracy and scalability of the method for large polycrystals and increasing phase property contrast are investigated. [ABSTRACT FROM AUTHOR]

Na 2 Ti 4 O 9 (NTO), an important chemical material, is used in chemical pigments, lithium ion batteries, catalyst carriers, and other fields. Nanoscale NTO crystal was firstly obtained by solvothermal process in this study, and the reactant conditions (time, temperature, solvent, and concentration of NaOH solution) for preparing NTO crystal were investigated. The result reveals that the as-prepared NTO crystal with one-dimensional (1D) rod-like morphology can be obtained in a solvent environment with H 2 O to C 2 H 5 OH via solvothermal process. And then investigating the formation mechanism of 1D NTO crystal based on the solvothermal soft chemical method. In addition, NTO crystal was utilized as the precursor for BaTiO 3 (BT) crystal at desired condition. The [010]-oriented BT polycrystals were directly obtained with NTO precursor via hydrothermal process in low concentration of Ba(OH) 2 solution. The transformation mechanism between BT polycrystals and NTO precursor was revealed, and the process of obtaining functional materials directly from NTO precursor was discussed. The study provides a novel way for the development of small-size barium titanate based functional materials. [ABSTRACT FROM AUTHOR]

TiAl alloys stand out for low density, high specific strength, and excellent creep resistance, making them promising for high‐temperature aerospace applications. However, traditional TiAl alloys suffer from poor room‐temperature ductility and low service temperature that limit their critical applications in aerospace structures. To address these issues, research has focused on improving the mechanical properties of TiAl alloys through alloying and microstructural design. After decades of effort, the evolution of TiAl alloys has progressed from polycrystalline TiAl to high‐performance polysynthetic twinned (PST) TiAl single crystals. The well‐aligned PST TiAl single crystals enriched with Nb enable an excellent combination of strength and ductility, significantly outperforming polycrystalline TiAl alloys. This review summarizes recent progress on TiAl alloys, particularly focusing on newly developed PST single crystals. First, the development history of TiAl alloys is overviewed; then their crystal structures, phase diagrams, and typical microstructures are systematically discussed, along with the design strategies based on alloying elements. Additionally, recent advances in TiAl columnar crystals, which are between polycrystals and single crystals, are reviewed. Subsequently, the mechanical anisotropy, preparation methods, and superior mechanical properties of the PST single crystals are analyzed in detail. The final remark highlights the future development and application prospects of TiAl alloys. [ABSTRACT FROM AUTHOR]

X-ray excited radioluminescence was demonstrated in Pr-doped lithium niobate polycrystalline samples with varying lithium-to-niobium ratios (R LN). The samples' phase structures, excitation and emission spectra, and radioluminescence were experimentally analyzed to investigate the tuning effects of R LN. Theoretical calculations based on Density Functional Theory (DFT) were conducted to elucidate the underlying mechanisms, and thermoluminescence curves were measured to verify the predictions of the theoretical analysis. We suggest that both photoluminescence and radioluminescence properties can be effectively tailored by adjusting the crystal structure, as well as the depth and density of electron traps within the LiNbO 3 :Pr matrix through R LN modulation. This research contributes to the development and practical implementation of scintillation materials derived from rare-earth-doped lithium niobate. [ABSTRACT FROM AUTHOR]

Hydrogenated two-dimensional (2D) Si nanosheet is a layered semiconductor synthesized by topotactic conversion of CaSi2 in HCl solution at low temperatures. The unavailability of scalable thin film deposition techniques has hindered the experimental analysis of physical properties. This study has investigated the synthesis of CaSi2 films by close-spaced evaporation and their topotactic conversion to 2D Si nanosheet films. A single-phase CaSi2 (6R) formation window was identified in the growth temperature range of 800–950 °C. Secondary phases (CaSi and Si polycrystals) formed outside the optimal window have also been identified. The x-ray pole figure of the representative CaSi2 film has shown that the film grows epitaxially with two epitaxial variants on the Si(111) surface with (0001) orientation. The CaSi2 films with and without the Si polycrystals have been subjected to low-temperature HCl solution treatment. Mostly hydrogenated 2D Si nanosheet films were synthesized without the Si polycrystals, while CaSi2 remained with the Si polycrystals, highlighting the importance of single-phase CaSi2 films. [ABSTRACT FROM AUTHOR]

Grain boundary plays a vital role in thermoelectric transports, leading to distinct properties between single crystals and polycrystals. Manipulating the grain boundary to realize good thermoelectric properties in polycrystals similar as those of single crystals is a long-standing task, but it is quite challenging. Herein, we develop a liquid-phase sintering strategy to successfully introduce Mg2Cu nano-sintering-aid into the grain boundaries of Mg3(Bi, Sb)2-based materials. The nano-aid helps to enlarge the average grain size to 23.7 μm and effectively scatter phonons, leading to excellent electrical transports similar as those of single crystals and ultralow lattice thermal conductivity as well as exceptional thermoelectric figure of merit (1.5 at 500 K) and conversion efficiency (7.4% under temperature difference of 207 K). This work provides a simple but effective strategy for the fabrication of high-performance polycrystals for large-scale applications. The authors develop a liquid-phase sintering strategy to effectively enlarge material's grain sizes, thereby achieving single crystal-like electronic transport properties in polycrystalline Mg3(Bi, Sb)2. [ABSTRACT FROM AUTHOR]

Small‐angle X‐ray tensor tomography and the related wide‐angle X‐ray tensor tomography are X‐ray imaging techniques that tomographically reconstruct the anisotropic scattering density of extended samples. In previous studies, these methods have been used to image samples where the scattering density depends slowly on the direction of scattering, typically modeling the directionality, i.e. the texture, with a spherical harmonics expansion up until order ℓ = 8 or lower. This study investigates the performance of several established algorithms from small‐angle X‐ray tensor tomography on samples with a faster variation as a function of scattering direction and compares their expected and achieved performance. The various algorithms are tested using wide‐angle scattering data from an as‐drawn steel wire with known texture to establish the viability of the tensor tomography approach for such samples and to compare the performance of existing algorithms. [ABSTRACT FROM AUTHOR]

The necessity for high operational temperatures presents a considerable obstacle to the commercial viability of solid oxide fuel cells (SOFCs). The introduction of active co-dopant ions to polycrystalline solid structures can directly impact the physiochemical and electrical properties of the resulting composites including crystallite size, lattice parameters, ionic and electronic conductivity, sinterability, and mechanical strength. This study proposes cobalt–iron-substituted gadolinium-doped ceria (CoxFe1-xGDC) as an innovative, nickel-free anode composite for developing ceramic fuel cells. A new co-precipitation technique using ammonium tartrate as the precipitant in a multi-cationic solution with Co2+, Gd3+, Fe3+, and Ce3+ ions was utilized. The physicochemical and morphological characteristics of the synthesized samples were systematically analysed using a comprehensive set of techniques, including DSC/TGA for a thermal analysis, XRD for a crystallographic analysis, SEM/EDX for a morphological and elemental analysis, FT-IR for a chemical bonding analysis, and Raman spectroscopy for a vibrational analysis. The morphological analysis, SEM, showed the formation of nanoparticles (≤15 nm), which corresponded well with the crystal size determined by the XRD analysis, which was within the range of ≤10 nm. The fabrication of single SOFC bilayers occurred within an electrolyte-supported structure, with the use of the GDC as the electrolyte layer and the CoO–Fe2O3/GDC composite as the anode. SEM imaging and the EIS analysis were utilized to examine the fabricated symmetrical cells. [ABSTRACT FROM AUTHOR]

The investigation of strain hardening in metals is complex, with the outcome depending on experimental conditions, that may involve microstructural history, temperature and loading rate. Hardening is commonly measured, after mechanical processing, through controlled mechanical testing, in ways that either distinguish elastic (stress) from total deformation measurements, or by identifying plastic slip contributions. In this paper, we conjecture that hardening effects can be unraveled through statistical analysis of total strain fluctuations during the evolution sequence of profiles, measured in-situ, through digital image correlation. In particular, we hypothesize that the work hardening exponent is related, through a power-law relationship, to a particular exponent arising from principal component analysis. We demonstrate a scaling analysis for synthetic data produced by widely applicable crystal plasticity models for polycrystalline solids. [ABSTRACT FROM AUTHOR]

A sustainable solution to the energy crisis may be found in thermoelectric materials and generators, capable of transforming thermal energy into electrical energy or vice versa. SnSe is one of the emerging thermoelectric materials with distinctive properties. The main advantages of this compound are earth-abundant, inexpensive, non-toxic and it is also known for its high thermoelectric performance. Here we prepared Bi/Te co-doped SnSe polycrystals; whereas, Bi and Te are added with different compositions such as (x = 0.0,0.02,0.04,0.06 and y = 0.03) in (Sn1-xBixSe1-YTeY) matrix by using the solid-state reaction method. XRD data confirms the samples belong to the orthorhombic crystal system with the Pnma space group. DFT calculations were used to see structural stability and electronic properties for pure and doped SnSe samples. Temperature-dependent semiconducting behavior of the samples has been demonstrated by electrical resistivity. The Seebeck coefficient, correlated with carrier concentration and mobility, validates the p-type behavior for the pristine samples and the n-type behavior for co-doped samples. The dominant behavior of phonon scattering has been demonstrated by thermal conductivity analysis. After co-doping there is decrement in total thermal conductivity was observed which 1.3 times lower than SnSe. A theoretical calculation was used to validate experimental results to estimate electrical properties, Seebeck coefficient, specific heat capacity, thermal conductivity, and power factor using Quantum espresso code with Boltzmann transport Equation. 4% Bi-doped sample displayed a significant increment in electrical conductivity and an enhanced Seebeck coefficient, which led to the power factor enhancement of approximately 2.0 times in contrast to the pristine sample and enhanced ZT of about 0.055 which is 3.43 times higher than the pristine SnSe. [ABSTRACT FROM AUTHOR]

0D organic–inorganic metal halides (OIMHs) with intriguing luminescence encoded in their diverse crystal structure open wide opportunities for next‐generation optoelectronics. Yet, this structural diversity makes their precise synthesis challenging. Here, a facile yet efficient off‐stoichiometry antisolvent precipitation protocol is devised to synthesize pure Bmpip2PbBr4 (Bmpip = 1‐butyl‐1‐methylpiperidinium) polycrystals. Optical investigations reveal that the key to suppressing the by‐product, Bmpip9[Pb3Br11][PbBr4]2, generally occurring in a typical stoichiometric synthesis is to create a Br‐rich environment to promote the [PbBr4]2− formation while suppressing the formation of [Pb3Br11]5−. Moreover, this off‐sociometric protocol can be extended to the precise synthesis of Bzmim3SbCl6 (Bzmim = 1‐benzyl‐3‐methylimidazolium) polycrystals through the meticulous control of [SbCl6]3− formation in the solution. The resulting Bzmim3SbCl6 polycrystals show a nominal light yield of 24600 photons MeV−1, which is 6.8 times higher than that of its by‐product, namely Bzmim2SbCl5, and outperforms that of commercial LuAG:Ce. As a result, the scintillators made of Bzmim3SbCl6@PMMA achieve a decent spatial resolution of 8.3 lp mm−1. This work highlights the importance of regulating the metal polyhalide intermediates in precisely synthesizing 0D OIMHs. [ABSTRACT FROM AUTHOR]

All‐inorganic CsPbI3 perovskite is a promising emitter for deep‐red light‐emitting diodes (LEDs). However, presently fabricated CsPbI3 polycrystalline films are composed of island‐like polycrystals, encountering the problems of serious interface current leakage and low‐efficiency carrier radiative recombination. Here, a CsPbI3‐xBrx quantum dots (QDs) matrix encapsulated CsPbI3 polycrystal film is reported to address the low‐efficiency issue of island‐like CsPbI3 polycrystalline film applied in deep‐red LEDs. The developed QDs matrix encapsulation strategy has two benefits. One is the filling of void space in the island‐like CsPbI3 polycrystal film to suppress the interface current leakage. The other more important benefit is utilizing the strong carrier confinement effect of QDs to strengthen the formation of excitons in the composite film and thus improve the electroluminescence efficiency. Moreover, interesting grain growth is found between CsPbI3‐xBrx QDs and CsPbI3 polycrystals, which further enhances the exciton transfer effect brought by the QDs matrix and optoelectronic properties of the fabricated composite films. Based on the obtained high‐quality QDs/polycrystal composite films, efficient and bright deep‐red LEDs are achieved with a peak external quantum efficiency of 15.24% and a maximum luminance of 3691 cd m−2. [ABSTRACT FROM AUTHOR]

The work is devoted to the study of the second-harmonic generation (SHG) process as a result of random quasi-phase-matching of thulium laser radiation in ZnSe polycrystals. A linear dependence of the SHG efficiency on the nonlinear medium length has been observed in the experiment. The efficiencies of SHG in ZnSe polycrystals with average grain sizes from 35 μ m to 380 μ m were compared. The obtained results are in good agreement with the theory in the case of a Gaussian grain size distribution. [ABSTRACT FROM AUTHOR]

Various types of grain growth behavior have been observed in polycrystals with faceted boundaries. The grain growth behavior observed in many different ceramic as well as metallic systems has been well explained by the mixed mechanism principle of grain growth and microstructural evolution. However, relatively few studies have considered repetitive grain growth in materials. To examine the generality of the microstructural evolution principle, two cases of repetitive grain growth during solid-state sintering are considered, one metallic (Ni) and one ceramic system (BaTiO 3). The observed repetitive grain growth behavior with an increased sintering temperature (in the case of Ni) and sintering time (in the case of BaTiO 3) supports well the generality of the mixed mechanism principle. [ABSTRACT FROM AUTHOR]

Inorganic lead-free metal halide perovskites are being rigorously explored as a substitute for organic lead-based materials for various energy device applications. Germanium as a replacement for lead has been proven to give exemplary results theoretically, and there have been promising results. The current work presents the investigation of CsGeI3 (CGI) polycrystals grown using a solution-free melt-growth technique with low-cost precursors. A soak-ramp profile was designed to synthesize polycrystalline powders, which were evaluated for stability. X-ray diffraction and Raman spectroscopy analysis suggest the formation of CsGeI3 perovskite powders, matching the reported literature. Diffuse reflectance spectroscopy measurements showed the bandgap of the polycrystals to be around 1.6 eV. A prominent photoluminescence peak was obtained at 767 nm. The powders were examined using thermogravimetric analysis to assess the thermal degradation pathways. The as-grown inorganic perovskite polycrystals were relatively stable during storage under ambient conditions. Theoretical studies were also carried out to support the experimental data. Calculations were performed with different approximations, including local density approximation (LDA), generalized gradient approximation (GGA), and Heyd–Scuseria–Ernzerhof (HSE) approximation, out of which the HSE approximation yielded the most accurate results that matched the experimental findings. Moreover, for the CGI device with Ag electrodes simulated using SCAPS-1D software, highest incident photon-to-electron conversion efficiency was observed. The obtained optical and structural properties indicate the suitability of the synthesized CsGeI3 perovskite polycrystals for photovoltaic applications, specifically solar cells and light-emitting diodes. [ABSTRACT FROM AUTHOR]

We study low-salt, binary aqueous suspensions of charged colloidal spheres of size ratio Γ = 0.57, number densities below the eutectic number density nE, and number fractions of p = 1.00–0.40. The typical phase obtained by solidification from a homogeneous shear-melt is a substitutional alloy with a body centered cubic structure. In strictly gas-tight vials, the polycrystalline solid is stable against melting and further phase transformation for extended times. For comparison, we also prepare the same samples by slow, mechanically undisturbed deionization in commercial slit cells. These cells feature a complex but well reproducible sequence of global and local gradients in salt concentration, number density, and composition as induced by successive deionization, phoretic transport, and differential settling of the components, respectively. Moreover, they provide an extended bottom surface suitable for heterogeneous nucleation of the β-phase. We give a detailed qualitative characterization of the crystallization processes using imaging and optical microscopy. By contrast to the bulk samples, the initial alloy formation is not volume-filling, and we now observe also α- and β-phases with low solubility of the odd component. In addition to the initial homogeneous nucleation route, the interplay of gradients opens various further crystallization and transformation pathways leading to a great diversity of microstructures. Upon a subsequent increase in salt concentration, the crystals melt again. Wall-based, pebble-shaped β-phase crystals and facetted α-crystals melt last. Our observations suggest that the substitutional alloys formed in bulk experiments by homogeneous nucleation and subsequent growth are mechanically stable in the absence of solid–fluid interfaces but thermodynamically metastable. [ABSTRACT FROM AUTHOR]

Solution growth is a promising method for rapidly and stably preparing high-quality silicon carbide (SiC) single crystals. However, the coexistence of polycrystalline parasitism and solid inclusions during the growth of SiC in high-temperature solutions above 1800 °C still poses a serious threat to the quality of single crystals. Herein, we introduce an innovative Mn-based cosolvent for controlling the stable and fast growth of cubic-type silicon carbide (3C–SiC) single crystals at low temperatures. Firstly, our thermodynamic analysis reveals that SiC is the only stable solid compound in the low-temperature solution (1500–1600 °C) of the Si–Mn–C system, which is an important condition for the stable growth of crystals. Compared to typical solvents like Si–Cr, Si–Ti, and Si–Fe, the Si–Mn solvent exhibits the highest solubility and supersaturation for carbon. Secondly, our solubility calculations of SiC in the solvent show that the Mn-rich solvent can significantly increase the solubility of SiC. Thirdly, we successfully grew 3C–SiC single crystals from Si–Mn solution at 1500 °C without other SiC polymorphs produced. Rapid growth of SiC crystals in Mn-rich solution was achieved by modulating the content of Mn. Our work highlights the superiority of Si–Mn cosolvents in facilitating rapid growth of 3C–SiC single crystals at low temperatures. It introduces a novel approach by applying phase diagram calculation techniques to design suitable solvent systems for the solution growth of SiC single crystals. [ABSTRACT FROM AUTHOR]

The thermally stable zirconium-based MOF, UiO-66, was employed for the preparation of bonded porous-layer open-tubular (PLOT) GC columns. The synthesis included the in situ growth of the UiO-66 film on the inner wall of the capillary through a one-step solvothermal procedure. SEM–EDX analysis revealed the formation of a thin, continuous, uniform, and compact layer of UiO-66 polycrystals on the functionalized inner wall of the column. The average polarity (ΔIav = 700) and the McReynolds constants reflected the polar nature of the UiO-66 stationary phase. Several mixtures of small organic compounds and real samples were used to evaluate the separation performance of the fabricated columns. Linear alkanes from n-pentane to n-decane were baseline separated within 1.35 min. Also, a series of six n-alkylbenzenes (C3–C8) were separated within 3 min with a minimum resolution of 3.09, whereas monohalobenzene mixtures were separated at 220 °C within 14s. UiO-66 PLOT columns are ideally suited for the isothermal separation of chlorobenzene structural isomers at 210 °C within 45 s with Rs ≥ 1.37. The prepared column featured outstanding thermal stability (up to 450 °C) without any observed bleeding or significant impact on its performance. This feature enabled the analysis of various petroleum-based samples. [ABSTRACT FROM AUTHOR]

The CaAl2SiO6 (CASO) aluminosilicate polycrystals doped with Ce3+ and Nd3+ ions have been synthesized using the sol–gel method. The XRD diffractograms, excitation and emission spectra, as well as the decay time profiles were measured and discussed. The energies of Nd3+ levels in CASO polycrystals were assigned. A series of crystalline powders were divided into two groups, with slightly different crystal symmetry. The CIE chromatic coordinates and colour purity were calculated. Refractive indices and bandgap energies were estimated. The influence of spectroscopic properties, depending on the symmetry and doping ratio, was analysed. Obtained research results explain the influence of doped ions on the spectroscopic properties of CaAl2SiO6 and provide a new perspective on aluminosilicate compounds. [ABSTRACT FROM AUTHOR]

Octreotide is the first synthetic peptide hormone, consisting of eight amino acids, that mimics the activity of somatostatin, a natural hormone in the body. During the past decades, advanced instrumentation and crystallographic software have established X-Ray Powder Diffraction (XRPD) as a valuable tool for extracting structural information from biological macromolecules. The latter was demonstrated by the successful structural determination of octreotide at a remarkably high d-spacing resolution (1.87 Å) (PDB code: 6vc1). This study focuses on the response of octreotide to different humidity levels and temperatures, with a particular focus on the stability of the polycrystalline sample. XRPD measurements were accomplished employing an Anton Paar MHC-trans humidity-temperature chamber installed within a laboratory X'Pert Pro diffractometer (Malvern Panalytical). The chamber is employed to control and maintain precise humidity and temperature levels of samples during XRPD data collection. Pawley analysis of the collected data sets revealed that the octreotide polycrystalline sample is remarkably stable, and no structural transitions were observed. The compound retains its orthorhombic symmetry (space group: P212121, a = 18.57744(4) Å, b = 30.17338(6) Å, c = 39.70590(9) Å, d ~ 2.35 Å). However, a characteristic structural evolution in terms of lattice parameters and volume of the unit cell is reported mainly upon controlled relative humidity variation. In addition, an improvement in the signal-to-noise ratio in the XRPD data under a cycle of dehydration/rehydration is reported. These results underline the importance of considering the impact of environmental factors, such as humidity and temperature, in the context of structure-based drug design, thereby contributing to the development of more effective and stable pharmaceutical products. [ABSTRACT FROM AUTHOR]

An impedance model based on the Volmer–Heyrovsky–Tafel mechanism was developed to study the kinetics of the hydrogen evolution reaction on polycrystalline gold electrodes at moderate overpotentials in aqueous H2SO4 (0.5 and 1.0 M) solutions. The model was optimized on data from potentiodynamic polarization and electrochemical impedance spectroscopy, and model parameters were extracted. Consistent with expectations, the magnitude of the impedance data indicated a higher rate of hydrogen evolution at lower pH. Also, the fractional surface coverage of adsorbed hydrogen ( θ H a d s ) increases with increasing overpotential but the small value of θ H a d s indicates only weak adsorption of H on gold. Tafel slopes and exchange current densities were estimated to be in the range of 81–124 mV/dec, and 10−6 and 10−5 A/cm2 in H2SO4 (0.5 and 1.0 M), respectively. The results show that the model accounts well for the experimental data, such as the steady-state current density. Sensitivity analysis reveals that the electrochemical parameters ( α 1 ,   α 2 ,   k 1 0 ,   k − 1 0 ,   a n d   k 2 0) associated with the kinetics of the hydrogen evolution reaction have a major impact on the calculated impedance but the standard rate constant for hydrogen oxidation reaction ( k − 2 0) does not strongly affect the calculated impedance. [ABSTRACT FROM AUTHOR]

Polycrystalline and mesocrystalline zinc ferrite were successfully fabricated via a solvo-thermal method using different salt precursors. This study found that when iron sulfate salt was used as a precursor, polycrystalline zinc ferrite was formed. Polycrystalline zinc ferrite is a well-dispersed 400-nm sphere solid particle. Primary nano-crystals have highly preferred orientations; however, defects exist among the particles. When iron chloride salt was used as a substitute as a prime material, mesocrystalline zinc ferrite was synthesised. The products are shaped as hollow-spheres with an average size of approximately 500 nm and are composed of nano-crystal sub-units aligned in a highly oriented crystallographic structure. Zinc ferrite mesocrystalline samples have many voids, and the inter-spaces of their structure indicate the high porosity hollow-sphere architecture of zinc ferrite. The experimental results show that specific adsorption of Cl− and SO 4 2− ions on the surface plays a crucial role during the growth process of products with different morphologies and crystallographic structures. Cl− adsorption on the surface may promote the formation of mesocrystal hollow-sphere particles; whereas, SO 4 2− gives rise to polycrystalline solid spheres. The use of the as-prepared products as catalysts for the photo-Fenton degradation of Rhodamine B (RhB) with an H 2 O 2 oxidant under visible-light irradiation and the effects of reaction conditions, including pH, catalyst amount and H 2 O 2 contratentation on the removal of RhB, were investigated. The reuse of the catalysts and a possible catalytic mechanism were also proposed. These results indicate that mesocrystalline hollow-sphere zinc ferrite is a favourable catalyst for dye degradation photo-Fenton processes. [Display omitted] [ABSTRACT FROM AUTHOR]

N-type polycrystalline SnSe is considered as a highly promising candidates for thermoelectric applications due to facile processing, machinability, and scalability. However, existing efforts do not enable a peak ZT value exceeding 2.0 in n-type polycrystalline SnSe. Here, we realized a significant ZT enhancement by leveraging the synergistic effects of divacancy defect and introducing resonance level into the conduction band. The resonance level and increased density of states resulting from tungsten boost the Seebeck coefficient. The combination of the enhanced electrical conductivity (achieved by increasing carrier concentration through WCl6 doping and Se vacancies) and large Seebeck coefficient lead to a high power factor. Microstructural analyses reveal that the co-existence of divacancy defects (Se vacancies and Sn vacancies) and endotaxial W- and Cl-rich nanoprecipitates scatter phonons effectively, resulting in ultralow lattice conductivity. Ultimately, a record-high peak ZT of 2.2 at 773 K is achieved in n-type SnSe0.92 + 0.03WCl6. N-type polycrystalline SnSe shows inferior ZT to p-type polycrystalline due to its high thermal conductivity and lower power factor. The authors overcome the problem via the synergy of divacancy defect and introducing resonance level into the conduction band. [ABSTRACT FROM AUTHOR]

Extended defects, including exposed surfaces and grain boundaries (GBs), are critical to the properties of polycrystalline solid electrolytes in all‐solid‐state batteries (ASSBs). These defects can alter the mechanical and electronic properties of solid electrolytes, with direct manifestations in the performance of ASSBs. Here, by building a library of 590 surfaces and grain boundaries of 11 relevant solid electrolytes—including halides, oxides, and sulfides— their electronic, mechanical, and thermodynamic characteristics are linked to the functional properties of polycrystalline solid electrolytes. It is found that the energy required to mechanically "separate" grain boundaries can be significantly lower than in the bulk region of materials, which can trigger preferential cracking of solid electrolyte particles in the grain boundary regions. The brittleness of ceramic solid electrolytes, inferred from the predicted low fracture toughness at the grain boundaries, contributes to their cracking under local pressure imparted by lithium (sodium) penetration in the grain boundaries. Extended defects of solid electrolytes introduce new electronic interfacial states within bandgaps of solid electrolytes. These states alter and possibly increase locally the availability of free electrons and holes in solid electrolytes. Factoring effects arising from extended defects appear crucial to explain electrochemical and mechanical observations in ASSBs. [ABSTRACT FROM AUTHOR]

The grain growth behavior during an AC flash event was examined in 8 mol% yttria‐stabilized cubic zirconia (8Y‐CSZ) polycrystals. The effects of current/power densities on the grain growth behavior were investigated in 8Y‐CSZ samples with different specific surface areas at a constant sample temperature and applied field strength. The grain growth rate of flash‐treated 8Y‐CSZ was 300 times faster than that of heat‐treated 8Y‐CSZ at the same sample temperature in the absence of an electric current/field, suggesting that the promoted grain growth cannot be ascribed only to a thermal effect but also to an athermal effect occurring during the AC flash event. Moreover, the grain growth during the flash treatment strongly depends on the applied current/power densities and grain size; in particular, the grain growth showed enhancements with increasing applied current/power densities and for relatively small grain sizes. This result suggests that the grain boundary diffusivity of cations, which are regarded as the rate‐controlling species for grain growth, could be accelerated by tuning the current/power densities during the flash event. The grain growth mechanism was characterized using a grain growth exponent (n) value of 4.8 for the flash treatment at high current/power densities and using a conventional value of n = 3 under normal heat treatment conditions. The dependence of the grain growth behavior on the AC current/power density suggests that because the cation diffusivity is accelerated due to the formation of numerous point defects during the AC flash event, the grain growth mechanism might depend on the current/power densities and differ from that of conventional grain growth. [ABSTRACT FROM AUTHOR]

The recent COVID-19 pandemic has made everyone aware of the threat of viruses and the growing number of antibiotic-resistant bacteria. It has become necessary to find new methods to combat these hazards. One tool that could be used is UVC radiation, i.e., 100–280 nm. Currently, the available sources of this light are mercury vapor lamps. However, the modern world requires more compact, mercury-free, and less energy-consuming light sources. This work presents the results of our research on a new material in which efficient UVC radiation was obtained. Here, we present the results of research on Ca9Y(PO4)7 polycrystals doped with Pr3+ ions prepared using the solid-state method. The absorption, excitation, emission, and emission decay profiles of praseodymium(III) ions were measured and analyzed. The upconversion emission in the UVC region excited by blue light was observed. Parameters such as energy bandgap, refractive index, and thermal stability of luminescence were determined. The studied phosphate-based phosphor possesses promising characteristics that show its potential in luminescent applications in future use in medicine or for surface disinfection. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) panels are energy production elements that are directly and catastrophically affected by climatic conditions. In this study, the performances of monocrystalline and polycrystalline photovoltaic panels, which are most commonly used in photovoltaic systems, were experimentally examined in summer and winter seasons. A comparison was made of the factors affecting the electrical performance of PV panels in summer and winter seasons under geographical climatic conditions at Istanbul University—Cerrahpaşa Avcılar center. In this experimental study, monocrystalline and polycrystalline PV panels with a power of 100 W were used. By drawing the characteristic curves of the current–voltage–power parameters, which are the electrical output parameters of the PV panels, seasonal performance comparisons were made comparatively with different weather conditions following the instantaneous effect in Avcilar, Istanbul. [ABSTRACT FROM AUTHOR]

Low-yttria doped zirconia polycrystals (Y-TZP) have recently emerged as new fine-grained zirconia ceramics exhibiting a promising combination of high fracture toughness and strength. In this investigation, we optimized the strength and fracture toughness of 2Y-TZP ceramics prepared by gelcasting and pressureless sintering. The 2Y-TZP ceramics with optimized processing reached a mean biaxial strength of 1070 MPa, similar to the strength obtained for the standard 3Y-TZP ceramics. However, a higher transformability of tetragonal grains in 2Y-TZP ceramics resulted in a stronger transformation toughening effect compared with 3Y-TZP ceramics. The fracture toughness obtained for 2Y-TZP exceeded that of 3Y-TZP (7.7 vs. 5.2 MPa m0.5). The differences in the microstructure and toughening mechanism between 2Y-TZP and 3Y-TZP were described, and the potential benefits of the 2Y-TZP were discussed. [ABSTRACT FROM AUTHOR]

Calculating the elastic and mechanical characteristics of non‐crystalline solids can be challenging due to the high computational cost of ab initio methods and the low accuracy of empirical potentials. This paper proposes a computational technique for efficient calculations of mechanical properties of polycrystals, composites, and multi‐phase systems from atomistic simulations with high accuracy and reasonable computational cost. The calculated elastic moduli of polycrystalline diamond and their dependence on grain size are determined using a developed approach based on actively learned machine learning interatomic potentials (MLIPs). These potentials are trained on local fragments of the polycrystalline system, and ab initio calculations are used to compute forces, stresses, and energies. This technique allows researchers to perform extensive calculations of the mechanical properties of complex solids with different compositions and structures, achieving high accuracy and facilitating the transition from ideal (single crystal) systems to more realistic ones. [ABSTRACT FROM AUTHOR]

Photoluminescence, luminescence excitation spectra, and electrical conductivity of β-Ga2O3-In2O3 solid solutions were studied. For this purpose, polycrystalline samples of unintentionally doped (UID) and doped with Ca or Zr β-Ga2O3-In2O3 solid solution with 20% In were synthesized and characterized. All samples were obtained by the high-temperature solid-phase method from appropriate oxides at 1300 °C at low and high oxygen partial pressure. It was established that UID and doped with Ca2+ or Zr4+ samples synthesized in an oxygen atmosphere were highly resistive, while the samples synthesized in an argon atmosphere had high conductivity. The conductivity was the lowest in the samples doped with Ca2+ and was 10−13 Ω−1 cm−1, while in the samples doped with Zr4+, the electrical conductivity was the highest and reached 10−3 Ω−1 cm−1. The broadband luminescence of β-Ga2O3-In2O3 solid solution is a superposition of three elementary bands with maxima in the violet 3.08 eV, blue 2.73 eV, and green 2.45 eV regions of the spectrum. Doping with Ca2+ or Zr4+ impurities and varying the synthesis atmosphere led mainly to a redistribution of intensities between the elementary luminescence bands. The luminescence arises from the radiative recombination of charge carriers through donor–acceptor pairs and self-localized holes. Donors and acceptors are formed by native defects such as (Gai, VGa, VGaVo) or doping impurities (Zr4+, Ca2+). Unlike the luminescence spectra, the luminescence excitation spectra change significantly when the synthesis conditions vary or when doping with divalent impurities. The excitation band at 4.46 eV is due to electron transitions from the VGa or VGaVO acceptor levels to the conduction band. Electron transitions from acceptor levels of Ca2+ impurities are manifested in the intense excitation band at 4.1 eV. [ABSTRACT FROM AUTHOR]

Grain boundary solute segregation influences most bulk material properties, and understanding solute thermodynamics at grain boundaries is critical for engineering them. However, the vast grain boundary space in polycrystals is challenging to evaluate due to its size, especially for the intrinsically hard-to-compute segregation excess entropy. Here data science methods are used to generate a database of site-wise grain boundary segregation entropy spectra for 155 dilute binary alloys within the harmonic approximation. The spectral framework allows scale bridging between the calculated atomistic site-wise energy-entropy spectra and macroscopic segregation entropy estimates. The results affirm that macroscopic averaging is not sufficient: a spectral treatment of grain boundary segregation is needed to accurately model bulk temperature dependence of grain boundary solute segregation. The calculated spectral entropy database and thermodynamic framework can be applied for both understanding segregation experiments and alloy design exercises, paving the way to a finite-temperature grain boundary genome. [ABSTRACT FROM AUTHOR]

The work is devoted to the analysis of the nonlinear effects resulting from the influence of excess volumes of intergranular boundaries on the structure of segregations of impurity atoms in polycrystals. It is shown that the adsorption isotherm can describe the nonuniformities in the distribution of impurity atoms in the plane of an intergranular boundary. This suggests the existence of adsorption sites at the internal boundaries of polycrystals. It is proven that an excess volume of intergranular boundaries is the main parameter determining the magnitude of impurity segregations at the boundaries. [ABSTRACT FROM AUTHOR]

The paper reports the results of study of composition, emission, and optical properties of polycrystalline W and Mo samples implanted with Ba+ ions and coated with submonolayer Ba atoms by applying Auger electron spectroscopy, secondary electron emission coefficient σ technique, as well as the photoelectron quantum yield Y. The experimental part was carried out by using the instrumentation and under vacuum Р ≈ 10-6 Pa. It is shown that during the implantation of Ba ions in the surface layers of refractory metals, a mechanical mixture of the W + Ba and Mo-Ba types is formed. It has been established that the values of the coefficient of secondary electron emission σ and the quantum yield of photoelectrons Y at the same value of the work function еφ in the case of implantation of Ba+ ions are much larger than in the case of deposition of atoms. The obtained experimental results are substantiated by theoretical calculations. [ABSTRACT FROM AUTHOR]

Grain boundaries (GBs) are transitional, defective, and anisotropic interfaces between adjacent grains with different orientations. However, most models assume that the GB is an isotropic dielectric determined by itself and lacks formation information; these assumptions hinder the theoretical investigation of the effect GBs have on polycrystalline ferroelectrics at the mesoscopic scale. Here, a novel GB model based on the formation mechanism is established for ferroelectric polycrystals. It has been found that the Curie–Weiss temperature range, elastic coefficient, and permittivity of GBs are related to the orientation of adjacent grains and the polarization state. The shielding effect, polarization enhancement, domain continuity, and spontaneous polarization on the GBs are obtained in mesoscopic simulations based on this model. In addition, the proportion of GBs can significantly affect the electric field distribution in grains. It provides a mechanistic explanation for the relationship between the coercive electric field and the proportion of GBs in the previous experiment. By achieving a better mesoscopic description of GBs, the GB model proposed in this work provides an effective investigation tool for electromechanical, electrocaloric, and energy storage of polycrystalline functional materials. [ABSTRACT FROM AUTHOR]

Grain boundaries (GBs) serve not only as strong barriers to dislocation motion, but also as important carriers to accommodate plastic deformation in crystalline solids. During deformation, the inherent excess volume associated with loose atomic packing in GBs brings about a microscopic degree of freedom that can initiate GB plasticity, which is beyond the classic geometric description of GBs. However, identification of this atomistic process has long remained elusive due to its transient nature. Here, we use Au polycrystals to unveil a general and inherent route to initiating GB plasticity via a transient topological transition process triggered by the excess volume. This route underscores the general impact of a microscopic degree of freedom which is governed by a stress-triaxiality-based criterion. Our findings provide a missing perspective for developing a more comprehensive understanding of the role of GBs in plastic deformation. [ABSTRACT FROM AUTHOR]

Using the method of transmission electron microscopy (TEM) of thin foils, the nucleation and propagation of microcracks in various structures of the plastic zone in the polycrystalline low-stability copper–aluminum alloys are studied in the vicinity of their structural-phase transformation into a crack-bearing state. The evolution of misoriented dislocation substructures (DSSs), formed in the low-stability pre-transitional states in the vicinity of the cracking stability loss in the stage of developed plastic strain, is discussed. The relationship between the fine structure surrounding the microcracks and the dislocation substructure formed by the time of the material failure, i.e., the low-stability state of the material in the vicinity of its structural-phase transition into a into a crack-bearing state, is revealed. The principal factors, characterizing the dislocation density in these states of the material and the dislocation density in the substructures where microcracks nucleate, are identified. These factors are the misorientation boundaries of different origins and the long-range stress fields. The changes of the structure and the long-range stress fields are examined as a function of the distance from the microcracks and their tips. [ABSTRACT FROM AUTHOR]

Spray Pyrolysis (SP), a low-cost chemical procedure was employed to deposit ZnO thin films under optimum conditions at 350 °C using a predetermined precursor concentration of 0.1 M. This study investigates how post-air annealing affects the structural, compositional, morphological, optical, and electrical properties of ZnO thin films. The deposited films were heated by air at 400, 450 and 500 °C for 1 h. X-ray diffraction, scanning electron microscope, x-ray dispersive spectroscopy, Raman spectroscopy, Fourier Transform Infrared Spectroscopy, optical spectroscopy, and Hall effect studies were conducted to investigate how post-air annealing alters the properties of the as-deposited film. XRD measurements show that annealing resulted in the growth of polycrystalline hexagonal wurtzite without the formation of any other phases in ZnO films. When heated to 500 °C, the estimated crystallite size of the as-deposited film increased from 6.22 nm to 6.57 nm. The SEM show the creation of compact and tightly packed films, as well as the visible network of large grains during annealing. Raman and FTIR studies have validated the chemical structure, molecular interactions, and formation of chemical bonds in ZnO thin films. Optical studies show that the energy band gap widens during annealing. Optical profilometer studies verified the uniformity of the deposited film surface. According to Hall effect analysis, conversion of p to n type occurs at an annealing temperature of 450 °C. A ZnO-based MOS gas sensor was found to have better selectivity towards C2H5OH than other test gases such as NH3, NO2, and H2S. At room temperature, the sensor response and recovery time is shorter for NH3 than for C2H5OH test gas. In environmental monitoring, the present gas sensor can detect ethanol. [ABSTRACT FROM AUTHOR]

Image-based micromechanical models, necessary for the development of structure-property-response relations, are far from mature for complex microstructures with multi-modal distributions of morphological and crystallographic features, such as those occurring with cold spray-formed (CSF) aluminum alloys. These materials have a bimodal polycrystalline microstructure composed of recrystallized ultra-fine grains (UFGs) and deformed coarse grains (CGs) within prior particles. A prime reason is the lack of robust approaches for generating statistically equivalent virtual microstructures (SEVM) capturing the statistics of characteristic morphological and crystallographic features, such as grain size, crystallographic orientations, and misorientations. This paper introduces an approach, strategically integrating Generative Adversarial Network-based approaches for producing bimodal CSF AA7050 alloy microstructures, with the synthetic microstructure builder Dream3D for packing prior particles with CGs having statistically equivalent morphological and crystallographic descriptors to electron backscatter diffraction (EBSD) maps. An efficient finite element (FE) simulation approach is developed for the SEVMs to generate local and overall response functions through the creation of sub-volume elements (SVEs). [ABSTRACT FROM AUTHOR]

For the first time, isothermal pressureless flash sintering of 1.5 mol% yttria-stabilized zirconia (1.5YSZ) polycrystals designed for high toughness was performed in a 1-kHz alternating current field (120 V·cm−1). The parameters governing tetragonal phase stability and densification needed to maximize the toughness of 1.5YSZ were investigated by varying the applied current density limit and holding time. A sample with relative density exceeding 98% and indentation toughness of about 13 MPa·m0.5 was sintered at 1100°C by applying 40 mA·mm−2 to the green body for 2 min, where the average steady-state temperature during flash reached 1330°C. Unlike flash sintering of conventional oxide ceramics, the applied current density and densification were not positively correlated despite pore closure. While Joule heating intensified when applying higher current densities, sample densification was hindered as the accelerated grain growth resulted in intergranular cracks which were generated by spontaneous tetragonal-to-monoclinic martensitic phase transformation during cooling. [Display omitted] • First study on flash sintering of high-toughness 1.5 mol% yttria-stabilized zirconia. • Sample with relative density > 98% and toughness of about 13 MPa·m0.5 was produced in 2 min. • Applying higher current density promoted grain growth and hindered densification. • Tetragonal phase stability degraded with increasing grain size. • Cracks formed around monoclinic grains deteriorated sample density and toughness. [ABSTRACT FROM AUTHOR]

The volume average of the constituting properties of a textured polycrystalline aggregate (the Voigt average) provides a simple way to estimate the effective properties of such an aggregate in terms of its crystallographic symmetry, texture symmetry, and the properties of the constituting crystallites. Despite the interest in estimate or characterizing flexoelectric properties, few studies have addressed the problem of finding effective flexoelectric properties from the continuum phases of the constituents. Instead, most of them focus on single-crystals at the atomic level. This study provides, for the first time, closed-form expressions that allow the direct flexoelectric coefficients to be computed for textured polycrystalline dielectrics. Crystallites can belong to any class of cubic symmetry or to the tetragonal T I Laue group, while no restriction is imposed on texture symmetry. These expressions are reduced to very simple ones when cubic crystallites with fiber texture are considered. The proposed formulation provides information on the matrix structure of the homogenized material related to the crystallographic symmetry and texture. We close with some illustrative examples. • Simple algebraic formulas for the 54 direct flexoelectric constants of textured polycrystals. • Valid for any cubic symmetry or tetragonal TI Laue group, no restrictions on texture. • Simplified expressions for cubic crystallites with fiber texture. • Flexoelectric tensor symmetries for isotropic, cubic and tetragonal crystals described in detail. [ABSTRACT FROM AUTHOR]

Low activator concentration in upconversion phosphors has been a hindrance in improving luminescence performance. Herein, we report an Er3+ doping concentration as high as 30 at. % in the CaLuAlO4 upconversion host. The CaLuAlO4:Er3+ phosphors were prepared by the traditional high-temperature solid-state method. Under the excitation of a 980 nm laser, the optimal concentration of Er3+ approaches 30% according to the total integrated intensity of red and green upconversion luminescence. This quenching concentration is one order of magnitude higher than that in the traditional Er3+ doped upconversion polycrystals. The results obtained from first-principles calculations suggest that there are no in-plane or chain rare-earth ions in the cell. This increases the difficulty of propagating excitation energy to quench centers and is advantageous for high doping concentration. Our work can spark people's interest in the research and application of highly doped upconversion phosphors. [ABSTRACT FROM AUTHOR]

The molecular dynamics method is conducted to study the mechanical properties and plastic deformation mechanism of composite materials ASSN‐WC with tungsten carbide (WC) grains added to 304 austenitic stainless steel nanopolycrystals (ASSN) during uniaxial tensile process. The results indicate that the overall strength of ASSN with void defect is decreased, and because of the larger shear model of WC crystal, the overall strength of ASSN‐WC material is improved, and its toughness is not significantly reduced. In the plastic deformation process, under low strain conditions, the main deformation mechanism inside polycrystals is dislocation slip. The slip of dislocations forms extended dislocations and stacking faults, which makes the grains deform. As the strain increases, the dislocation slip inside the grains becomes more intense, and deformation twins appear. The interaction between slip dislocations and grain boundaries makes the grain boundaries hinder the further deformation of the grains, and the strengthening effect on the local area of the material becomes more obvious. Meanwhile, in the process of strain increase, the WC grains do not rotate and deform. This can also effectively hinder the deformation of other grains on the adjacent edges and improve the stiffness of the composite material. [ABSTRACT FROM AUTHOR]

The mechanical properties of carbon polycrystalline materials are crucial because they determine how the material responds to external forces, such as stress and strain, and environmental conditions. By investigating the mechanical properties of carbon polycrystalline materials, researchers can develop insights into their strength, ductility, hardness, and other characteristics, which are vital for their practical applications in industries such as manufacturing, construction, and materials science. Molecular dynamics techniques enable the examination of various polycrystalline configurations and the assessment of their effectiveness. The present study investigates the effects of temperature on the mechanical properties of Carbon polycrystalline. The results show that the ultimate strength and Young’s modulus of the simulated polycrystal are 64.553 Gpa and 355.284 GPa, respectively. Also, the results showed that with increasing temperature to 320 K, Young’s modulus and ultimate strength of carbon polycrystalline increase to 363.185 and 69.417 GPa, respectively. With a further increasing the temperature to 350 k, these parameters decrease to 349.909 and 63.047 GPa. The observed increase in these parameters at lower temperatures may be attributed to the increased atomic mobility of the samples resulting from the initial temperature enlargement. The simulation results are expected to help further understand the influence of temperature on the mechanical properties of carbon polycrystalline materials. [ABSTRACT FROM AUTHOR]

In this thesis, the samples of dental zirconia were sintered to various temperatures (1250,1350, and 1450) °C, and subjected to friction between them in saliva at two different sliding speeds (200 and 400 revolutions per minute) and in various periods (10, 20, and 30 minutes) by using pin on disc wear testing machine, the wear rate was affected by several factors (sintering temperature, sliding speed, and sliding time). Where the rate of wear decreased by the increase of one of these factors with the stabilization of the other two factors. [ABSTRACT FROM AUTHOR]

With the improvement of research on the tooth surface and interface, the rock breaking technology of a polycrystalline diamond compact (PDC) bit has witnessed significant advancements and widespread applications in various domains. However, the current research on the tooth surface and interface is largely independent of each other, lacking integration between the two. This study aims to explore the influence of the connection between the tooth surface and interface on cutting efficiency and failure mechanisms during PDC bit cutting operations. Six different mating structures are selected for analysis, and the cutting process is simulated using Abaqus software in a consistent environment. The study examined the crushing specific energy, stress distribution, cutting force and temperature rise effect of different mating structures. Comparative analysis revealed that the efficiency and failure mechanism of the cutter are influenced by the interface shape, both within the same tooth shape and across different tooth shapes. Among the selected mating structures, the saddle-tooth surface with a radial interface exhibited superior performance in all aspects and demonstrated significant improvements. The findings provide a theoretical foundation for the study of the mechanism behind PDC cutter mating structures. [ABSTRACT FROM AUTHOR]

We propose a method to convert the channeling Rutherford backscattering spectrum yield map of a single crystal to a polycrystal through a matrix rotation technique. The rotation matrix is determined by the deviation of the crystal axial direction from the original z axis. The final yield map is created after averaging the rotated yields using the texture function as the weight factor. For highly oriented pyrolytic graphite (HOPG) exhibiting mosaic spread, the method leads to a Gaussian kernel averaging of the map obtained from a single crystal. The yield map of a single crystal is obtained by a simulation of ion trajectories in a potential field described by Moliere screened Coulomb potentials. Yield maps are calculated under various σ values (standard deviations of mosaic spread). The simulated results are compared with experimental results obtained using 1.2 MeV alpha particle. σ is extracted through the best fitting, demonstrating that the method can be used to obtain texture details. The effects of mosaic spread on minimum yield χ m i n and the half-width at half maximum of angular scans ψ 1 / 2 are systematically modeled and compared with previous theoretical equations. The study also shows that previous theoretical equations are valid only at small σ values. The proposed method can be applied to any type of polycrystal and is not limited to HOPG. It provides near-surface mosaic spread and crystallography information with a longitudinal depth resolution of tens of nanometers and is not influenced by grain shapes. [ABSTRACT FROM AUTHOR]

In this work, bulk Czochralski-grown single crystals of 10 mol. % Al2O3 alloyed β-Ga2O3—monoclinic 10% AGO or β-(Al0.1Ga0.9)2O3—are obtained, which show +0.20 eV increase in the bandgap compared with unintentionally doped β-Ga2O3. Further, growths of 33% AGO—β-(Al0.33Ga0.67)2O3—and 50% AGO—β-(Al0.5Ga0.5)2O3 or β-AlGaO3—produce polycrystalline single-phase monoclinic material (β-AGO). All three compositions are investigated by x-ray diffraction, Raman spectroscopy, optical absorption, and 27Al nuclear magnetic resonance (NMR). By investigating single phase β-AGO over a large range of Al2O3 concentrations (10–50 mol. %), broad trends in the lattice parameter, vibrational modes, optical bandgap, and crystallographic site preference are determined. All lattice parameters show a linear trend with Al incorporation. According to NMR, aluminum incorporates on both crystallographic sites of β-Ga2O3, with a slight preference for the octahedral (GaII) site, which becomes more disordered with increasing Al. Single crystals of 10% AGO were also characterized by x-ray rocking curve, transmission electron microscopy, purity (glow discharge mass spectroscopy and x-ray fluorescence), optical transmission (200 nm–20 μm wavelengths), and resistivity. These measurements suggest that electrical compensation by impurity acceptor doping is not the likely explanation for high resistivity, but rather the shift of a hydrogen level from a shallow donor to a deep acceptor due to Al alloying. Bulk crystals of β-(Al0.1Ga0.9)2O3 have the potential to be ultra-wide bandgap substrates for thin film growth, with a lattice parameter that may even allow higher Al concentration β-Ga2O3 single crystal thin films to be grown. [ABSTRACT FROM AUTHOR]

The FEM simulations of the ECAP including real conditions of the process – the friction between the metal extruded and the die walls, as well as, the channels rounding, were done here in two scales – macro- and micro-. The macroscopic analyses were done for isotopic material with a non-linear hardening using the UMAT user material procedure. The pure Lagrangian approach was applied here. The stress, strains and their increments, as well as, the deformation gradient tensor were recorded for selected finite elements in each calculation step. The displacements obtained in the macroscopic FEM analysis are then used as the kinematic input for the polycrystalline structure. The dislocation slip was included as the source of the plastic deformation here for the face-centered cubic structure. The results obtained with the use of the crystal plasticity show the heterogeneous distribution of stress and strain within the material associated with the grains anisotropy. The results in both micro- and macro- scales are coincident. The FEM analyses show the potential of the application of the crystal plasticity approach for solving elastic-plastic problems including the material forming processes.