Search Results (72)

Magnetic topological insulators (TIs) are promising candidates for realizing the quantum anomalous Hall effect (QAHE) and advancing the development of next-generation low-energy transistors and electronic devices. Doping Bi₂Se₃ with nano-carbon can introduce magnetic order and open the Dirac gap without introducing extrinsic magnetic impurities. In this work, the C_0.06Bi₂Se₃ single crystal was prepared using the Bridgman method, and their electrical and magnetotransport properties were systematically investigated. Temperature-dependent resistivity and magnetoresistance measurements revealed a magnetic-field-induced metal–insulator-like transition near 152 K. Angle-resolved photoemission spectroscopy (ARPES) detected an energy gap of about 43 meV at the Dirac point, confirming that carbon doping modulates the surface state and opens the gap. Pronounced Shubnikov–de Haas oscillations indicate high carrier mobility in C_0.06Bi₂Se₃. Furthermore, the temperature-dependent Kerr spectra shows that the spin relaxation behavior of C₀.₀₆Bi₂Se₃ differs significantly from that of pure Bi₂Se₃; the relaxation process of spin electrons from the surface state (τ_s) dominates the spin dynamics and exhibits distinct trends around 30 K and 150 K due to the interplay of the Dirac gap and impurity-induced states. These results demonstrate the potential of magnetic topological insulator C_0.06Bi₂Se₃ for novel electronic and spintronic applications. Full article

The novel fibrous composites of Al₆₁Cu₂₇Fe₁₂ alloy with a single-crystalline matrix and quasi-crystal phase fraction obtained in situ by directional solidification by the Bridgman method were studied to characterize the voids and their role in composites cracking. The voids were analyzed using light-optical and scanning electron microscopy to study their nature before and after uniaxial tensile tests. Tension tests were performed on plate-like samples up to rupture. The tensile fracture surfaces were also observed and analyzed. The single-crystallinity and crystalographic parameters of composites were studied using the X-ray Laue diffraction method. It was stated that such new type of composite is characterized by a relatively high void content with a ratio of approximately 2.6%. The composite’s cracking is initiated at voids and progress through the voids and stair steps in the matrix and the reinforcing fibers. Full article

Scintillators are important for a wide range of applications in detection and imaging. In this paper, the growth and performance results of advanced large-diameter thallium-based ternary halide crystals are presented. Intrinsic crystals of TlMgCl₃, TlCaCl₃, and other small-diameter TlCaBr₃, and TlCa(Cl,Br)₃, as well as europium-doped TlCa₂Br₅, TlCa(Cl,Br)₃, and TlSr₂I₅ are melt-grown by the Bridgman method. These compounds have a high effective atomic number (Z_eff) and physical densities due to thallium. The best crystal quality and energy resolution (FWHM) at 662 keV are observed for TlMgCl₃, TlCaCl₃, and TlSr₂I₅:Eu at 3.8%, 4.6%, and 3.5%, respectively. The primary decay constants for these compounds are in the range of 0.45 to 0.63 μs. These ternary Tl-halide compounds have proportional or linear response (±0.05%) to γ-rays above 40 keV. Full article

This study evaluates the perfection of the crystal structure of single-crystal turbine blade castings made from the CMSX-4 nickel superalloy. The analysis included primary and secondary crystal orientation measurements using the Ω-scan method and the novel OD-EFG X-ray diffractometer. The selected microstructural parameters of the single crystals were also analyzed, including the assessment of stereological parameters and the degree of porosity. A creep test was performed according to standard procedures and under conditions simulating real operational environments. The model single-crystal turbine blades were manufactured using the Bridgman–Stockbarger method, with variable withdrawal rates of 1 and 3 mm/min. Heat treatment of the single-crystal castings involved solution treatment followed by double aging. The evaluation of structural perfection was carried out in three states: as-cast, after solution heat treatment, and after double aging. The crystallographic orientation of the blades was determined on both the airfoil and the root part. The study determined how crystallographic orientation and microstructural parameters influence the creep resistance of the castings. It was found that in the as-cast condition, the greatest influence on high creep strength has a small deviation of the primary and constant value of secondary crystal orientation along the height of the blade casting. After heat treatment, the highest creep resistance was obtained for the blade manufactured at a withdrawal rate at 1 mm/min. Full article

The Bridgman method for single-crystal growth enables the formation of crystals at the lower end of the molten material by cooling it under a precisely controlled temperature gradient. This makes it particularly suitable for producing high-quality single-crystal materials. Over the years, the Bridgman technique has become widely adopted for growing single crystals of semiconductors, oxides, sulfides, fluorides, as well as various optoelectronic, magnetic, and piezoelectric materials. Recently, there has been growing interest in metal halide materials, with the growth of high-quality metal halide single crystals emerging as a major focus for both the scientific community and industry. However, traditional solution-based single-crystal growth methods have several limitations, such as slow growth rates, inconsistent crystal quality, challenges in solvent selection, and difficulties in controlling saturation levels. These issues present significant obstacles, particularly when large, defect-free, high-quality single crystals are needed for certain high-performance materials. As a result, the Bridgman method has emerged as an effective solution to overcome these challenges. This review provides an overview of various categories of metal halide single-crystal systems grown using the Bridgman method in recent years. The systems are classified based on their dimensionality into three-dimensional, two-dimensional, and zero-dimensional metal halide structures. Furthermore, we highlight novel metal halide single crystals developed through the Bridgman technique. Additionally, we offer a brief introduction to the structures, properties, and applications of these single crystals, underscoring the crucial role of the Bridgman method in advancing research in this field. Full article

This study reviews the advanced anti-counterfeiting applications of CsCdCl₃, a lead-free all-inorganic perovskite crystal exhibiting dynamic luminescent properties responsive to temperature and UV light. Using synthesis methods such as Bridgman and hydrothermal techniques and incorporating dopants like bromine and tellurium, this research achieves improved luminescent stability, spectral diversity, and afterglow characteristics in CsCdCl₃. The crystal demonstrates extended afterglow, photochromic shifts, and temperature-sensitive luminescence, enabling applications in 4D encoding for secure data encryption and in cold-chain temperature monitoring for pharmaceuticals. Despite these promising attributes, the challenges related to photostability, batch consistency, and environmental resilience persist, necessitating further exploration into the optimized synthesis and doping strategies to enhance material stability. These findings underscore the potential of CsCdCl₃ for high-security information storage, pharmaceutical anti-counterfeiting, and real-time environmental sensing, positioning it as a valuable material for the next generation of secure, intelligent packaging solutions. Full article

The material family halide perovskites has been critical in recent room-temperature radiation detection semiconductor research. Cesium lead bromide (CsPbBr₃) is a halide perovskite that exhibits characteristics of a semiconductor that would be suitable for applications in various fields. In this paper, we report on the correlations between material purification and crystal material properties. Crystal boules of CsPbX₃ (where X = Cl, Br, I, or mixed) were grown with the Bridgman growth method. We describe in great detail the fabrication techniques used to prepare sample surfaces for contact deposition and sample testing. Current–voltage measurements, UV–Vis and photocurrent spectroscopy, as well as photoluminescence measurements, were carried out for material characterization. Bulk resistivity values of up to 3.0 × 10⁹ Ω∙cm and surface resistivity values of 1.3 × 10¹¹ Ω/□ indicate that the material can be used for low-noise semiconductor detector applications. Preliminary radiation detectors were fabricated, and using photocurrent measurements we have estimated a value of the mobility–lifetime product for holes (μτ)_h of 2.8 × 10⁻⁵ cm²/V. The results from the sample testing can shed light on ways to improve the crystal properties for future work, not only for CsPbX₃ but also other halide perovskites. Full article

In this study, we report the growth and comprehensive spectroscopic analysis of TmF₃-doped CaF₂ crystals, grown using the vertical Bridgman method. The optical absorption and photoluminescence properties of both trivalent (Tm³⁺) and divalent (Tm²⁺) thulium ions were investigated. Optical absorption spectra in the UV-VIS-NIR range reveal characteristic transitions of Tm³⁺ ions, as well as weaker absorption bands corresponding to Tm²⁺ ions. The Judd–Ofelt (JO) formalism was applied to determine the intensity parameters Ω₂, Ω₄, and Ω₆, which were used to calculate radiative transition probabilities, branching ratios, and radiative lifetimes for the Tm³⁺ ions. The emission spectra showed concentration-dependent quenching effects, with significant emissions observed for the concentration of 0.1 mol% TmF₃ under excitation at 260 nm and 353 nm for Tm³⁺ ions and at 305 nm for Tm²⁺ ions. A new UV emission associated with divalent Thulium is reported. The results indicate that higher TmF₃ concentrations lead to increased non-radiative energy transfer, which reduces luminescence efficiency. These findings contribute to the understanding of the optical behavior of Tm-doped fluoride crystals, with implications for their application in laser technologies and radiation dosimetry. Full article

Co₇Zn₇Mn₆ is a $\beta$-Mn-type alloy belonging to the Co_xZn_yMn_z ($x+y+z=20$) family that notoriously features a skyrmionic magnetic phase below the ferromagnetic ordering temperature and, in addition, a reentrant spin glass transition at low temperatures. In this work, we have studied the effect of partial substitution of Mn by Fe in the magnetic properties of this alloy. Samples of Co₇Zn₇Mn_6−xFe_x, $0\le x\le 1$, were synthesised using the Bridgman–Stockbarger method, and their structure and composition were fully characterised by XRD and EDS. VSM and AC susceptibility measurements show that the partial substitution of Mn by Fe increases $T_{\mathrm{C}}$ and the skyrmionic region of the magnetic phase diagram is suppressed for $x>0.5$. The AC susceptibility behaviour at low temperatures can be ascribed to the presence of a reentrant spin glass state observed for all compositions, with a spin glass freezing temperature, $T_{\mathrm{g}}$, that shifts to lower temperatures as the Fe content increases. Full article

SiMo ductile cast iron combines ease of part fabrication with good mechanical properties, including a usable plasticity range. Its poor corrosion resistance inherited from grey cast iron could be alleviated through alloying with Al or Cr additions capable of forming a dense oxide scale protecting the substrate. However, the presence of Al and Cr in cast iron tends to make the material brittle, and their optimum alloying additions need to be studied further. The present work was aimed at investigating the effect of crystallization rates on microstructure changes during directional crystallization of SiMo-type alloys with up to 3.5% Al and 2.4% Cr. The experiment was performed using the Bridgman–Stockbarger method. The tubular crucible was transferred from the hot section to cold section at rates ranging from 5 mm/h to 30 mm/h with a 4/5 crucible length and then quenched. The introduced Al promoted graphitization up to a point, wherein, at the highest applied addition, the graphite precipitation preceded crystallization of the rest of the melt. A rising level of Cr in these alloys from 1% to 2.4% resulted in the formation of low and high contents of pearlite, respectively. The higher crystallization rates proved effective in increasing the ferrite content at the expense of pearlite. In the investigated cast iron samples with smaller applied alloying additions, Widmanstätten ferrite or ausferrite, i.e., fine acircular phase, were often found. The switch from directional crystallization to quenching caused a transition from a liquid to solid state, which started with nucleation of islands of fine austenite dendrites with chunky graphite eutectic separating them. As these islands expanded, they pushed alloying additions to their sides, promoting carbide or pearlite formation in these places and forming a super-cell-like structure. The performed experiments helped gather information concerning the sensitivity of the microstructure of SiMo cast iron modified with Al and Cr to crystallization rates prevailing in heavy cast structures. Full article

Metallic materials are commonly characterized through tensile tests. For ductile metals, a consistent part of the test occurs after the necking onset. A first estimate of the post-necking behavior could be obtained by extrapolating the mathematical model that fits the pre-necking law. However, as well known, the accuracy of the predictions would not be guaranteed. Therefore, over the past decades many efforts have been devoted to dealing with the necking phenomenon. The most popular correction formula proposed by Bridgman is an analytical method based on the neck geometry. Despite being widely used, it may not be accurate at large strains due to the assumption of uniform distribution of the equivalent stress and equivalent strain in the specimen minimum cross-section. Starting from Bridgman’s idea and in order to overcome its limitations, the present paper develops an efficient method to calibrate the hardening law of isotropic metallic materials at large strains. The proposed method requires to record the outer contour of the necking zone during the test and to build a dataset of necking deformed shapes. Experimental quasi-static tensile tests were analyzed with the proposed approach, which appears promising when critically compared with other methods. Full article

PbF₂ single crystals are usually grown in the temperature gradient region by the Bridgman–Stockbarger method. Temperature distribution during the growth process is particularly important for the preparation of high-quality crystals. In this study, the temperature field during the growth of the PbF₂ single crystals was simulated based on the finite element method. The temperature distribution and temperature gradient changes in the crucible were investigated at different growth stages, including the seeding, shouldering, and iso-diameters stages. The calculated results show that as the crucible position continues downward during the growth process, the axial temperature gradient increases and then decreases from the bottom to the top of the crucible, with almost flat isotherms near the solid–liquid interface where the axial temperature gradient is larger. At the shoulder below the crucible, the solid–liquid interface was improved by adjusting the tilt angle. Furthermore, based on a novel design of the heat-insulating baffle, the concave solid–liquid interface in the iso-diameter stage can be effectively adjusted to realize a lower radial temperature gradient. This study provides theoretical guidance for the optimization of the growth of high-quality PbF₂ crystals by the Bridgman method. Full article

A series of lithium niobate crystals co-doped with uranium and indium was successfully grown by the modified vertical Bridgman method for the first time. With increasing In³⁺ ion doping concentration, the segregation coefficient of uranium and indium progressively deviated from 1. The structural refinement indicated that uranium ions with high valence preferred to occupy the Nb sites in LN: In, U crystals. LN: In_2.0, U_0.6 achieved multi-wavelength holographic writing with diffraction efficiency comparable to commercial crystals LN:Fe_0.3, demonstrating a response time that was four times shorter than LN:Fe_0.3. XPS analysis was employed to investigate the valence states of In³⁺ ions in LN: In_2.0, U_0.6, in which uranium ions presented three valences of +4, +5 and +6. Furthermore, the ‘real threshold concentration’ of In³⁺ ions in LN: In, U was calculated using the Li-vacancy model, which is consistent with the results obtained from the experimental study of the OH⁻ absorption spectrum. Discussions on the photorefractive centers in LN: In, U are also provided. This study not only demonstrates the impact of doping In³⁺ ions on the growth of LN:U crystals, but also offers new insights into the photorefractive properties of LN in the visible band. Full article

Finite element modeling for designing and optimizing lightweight titanium aerospace components requires advanced simulation tools with adequate material modeling. In this sense, a hybrid strategy is proposed in this work to identify the parameters of the Johnson–Cook plasticity and damage laws using a combined direct-inverse method. A direct calibration method for plasticity law is applied based on the literature-reported data of strain-stress curves from experimental tensile tests at different temperatures and strain rates. The triaxiliaty-dependent fracture parameters of the Johnson–Cook damage law at reference conditions of strain rate and temperature (d₁, d₂, and d₃) are calibrated with the direct method based on new data of experimental evolution of computed average fracture strain with the average stress triaxiality. The validation is performed with numerical results from an accurate micromechanics-based Ti64 model. The inverse calibration method is used to determine the strain rate and temperature-dependent damage parameters (d₄ and d₅) through large strain simulations of uniaxial tensile tests. The numerical results, including average strain and necking profile at fracture, are then utilized to calculate stress triaxiality by the Bridgman criterion for adjusting parameters d₄ and d₅. The calibrated model yields a 2.1% error for plasticity and 3.4% for fracture predictions. The experimental and simulated load-bearing capacity using the micromechanics damage model differed by only 1%. This demonstrates that the SC11–TNT model of Ti64 is reliable for identifying the Johnson–Cook damage law through the accurate use of inverse methods. The hybrid calibration strategy demonstrates the potential capability of the identified Johnson–Cook model to accurately predict the design load-carrying capacity of Ti64 aerospace components under different deformation rates and temperatures while accounting for material damage effects. Full article

The ³He gas is commonly used for the detection of thermal neutrons. However, with the depletion of ³He gas, there is a need to develop new solid scintillators for thermal neutron detection. Solid scintillators containing ⁶Li, which have large neutron capture cross-sections and a large amount of energy released by transmutation reactions, are commonly used as alternative candidates. However, only single-crystal scintillators are currently used, and their ⁶Li concentration is limited by their chemical composition. In this study, we designed, grew, and evaluated a new eutectic scintillator, Rb₂CeCl₅/LiCl, which can improve the ⁶Li concentration compared with single-crystal scintillators. Rb₂CeCl₅, which was selected as the scintillator phase, has excellent scintillator properties (light yield: 36,000 photons/MeV, decay time: mostly 24 ns, slightly 153 ns), and is less deliquescent than other halide scintillators. The crystal grown using the vertical Bridgman method exhibited a eutectic phase composed of Rb₂CeCl₅ and LiCl. The eutectic crystals exhibited Ce³⁺ 5d-4f emissions, with a peak between 360 and 370 nm. The Rb₂CeCl₅ phase was identified as the luminescent phase via cathodoluminescence mapping, and 16,000 photons/neutron of the light yield and 56.1 ns of the decay time were observed. This study indicates that the Rb₂CeCl₅/LiCl eutectic scintillator is a promising candidate for use in thermal neutron detectors. Full article