Properties Of Single-crystalline Research Articles

Interfacial Engineering for Controlled Crystal Mosaicity in Single-Crystalline Perovskite Films.

Organic-inorganic hybrid perovskites have attracted significant attention for optoelectronic applications due to their efficient photoconversion properties. However, grain boundaries and irregular crystal orientations in polycrystalline films remain issues. This study presents a method for producing crystalline-orientation-controlled perovskite single-crystal films using retarded solvent evaporation. It is shown that single-crystal films, grown via inverse temperature crystallizationwithin a confined space, exhibit enhanced optoelectronic property. Using interfacial polymer layer, this method produces high-quality perovskite single-crystalline films with varying crystal orientations. Density functional theory calculations confirm favorable adsorption energies for (110) surfaces with methylammonium iodide and PbI2 terminations on poly(3-hexylthiophene), and stronger adsorption for (224) surfaces with I and methylammonium terminations on polystyrene, influenced by repulsive forces between the thiophene group and the perovskite surface. The correlation between charge transport characteristics and perovskite single-crystalline properties highlights potential advancements in perovskite optoelectronics, improving device performance and reliability.

Impact of Lithium Sources on Growth Process and Structural Stability of Single‐Crystalline Li‐rich Layered Cathodes

Single‐crystalline (SC) Li‐rich layered oxides have garnered significant attention due to their inhibited lattice oxygen release and reduced crack formation compared with polycrystalline (PC) counterparts. However, it raises a crucial question regarding the selection of prevailing lithium sources—Li2CO3 and LiOH·H2O—for the solid‐state synthesis of SC cathodes, which critically impacts the technical route and future development of SC materials. Herein, a series of SC Li‐rich layered cathodes were synthesized using these two lithium sources. The SC materials prepared with LiOH·H2O (LRO−H) exhibited larger grain sizes compared with those using Li2CO3 (LRO−C). This can be attributed to the lower phase transition temperature of the precursor to spinel phase, which promotes further SC growth during solid‐state reactions. Furthermore, LRO−H demonstrated excellent electrochemical stability, whereas LRO−C exhibited superior initial capacities. To balance these attributes, a mixed lithium sources system (LRO−M) was proposed, showing superior Li+ diffusion kinetics and suppressed layered−to−spinel transformation, resulting in excellent rate performance and an extended battery lifespan. Altogether, these findings provide critical insights into the impact of lithium sources on the growth process, structural stability, and electrochemical properties of SC Li‐rich layered cathodes, guiding the synthesis and design of next‐generation cathode materials.

Field-induced effects in the spin liquid candidate PbCuTe2O6

${\mathrm{PbCuTe}}_{2}{\mathrm{O}}_{6}$ is considered to be one of the rare candidate materials for a three-dimensional quantum spin liquid (QSL). This assessment was based on the results of various magnetic experiments, performed mainly on polycrystalline material. More recent measurements on single crystals revealed an even more exotic behavior, yielding ferroelectric order below ${T}_{\text{FE}}\ensuremath{\approx}1\phantom{\rule{0.28em}{0ex}}\text{K}$, accompanied by distinct lattice distortions, and a somewhat modified magnetic response which is still consistent with a QSL. Here we report on low-temperature measurements of various thermodynamic, magnetic, and dielectric properties of single-crystalline ${\mathrm{PbCuTe}}_{2}{\mathrm{O}}_{6}$ in magnetic fields $B\ensuremath{\le}14.5\phantom{\rule{0.28em}{0ex}}\text{T}$. The combination of these various probes allows us to construct a detailed $B\text{\ensuremath{-}}T$ phase diagram including a ferroelectric phase for $B\ensuremath{\le}8$ T and a $B$-induced magnetic phase at $B\ensuremath{\ge}11$ T. These phases are preceded by or coincide with a structural transition from a cubic high-temperature phase into a distorted noncubic low-temperature state. The phase diagram discloses a ferroelectric quantum critical point at ${B}_{c1}=7.9\phantom{\rule{0.28em}{0ex}}\text{T}$, where the second-order phase transition line associated with ferroelectric order is suppressed to zero. In addition, a magnetic quantum phase transition is revealed at ${B}_{c2}=11\phantom{\rule{0.28em}{0ex}}\text{T}$. The corresponding phase transition to a field-induced magnetic order at $B>{B}_{c2}$ is likely to be of first order. Field-induced lattice distortions, observed in the state at $T>1$ K and which are assigned to the effect of spin-orbit interaction of the ${\mathrm{Cu}}^{2+}$ ions, are considered as the key mechanism by which the magnetic field couples to the dielectric degrees of freedom in this material.

Thermoelectric transport properties of single-crystalline ZrCoBi half-Heusler

Half-Heusler compounds are one of most promising thermoelectric materials for power generation at high temperatures. Recent studies focus on fine-grained polycrystalline samples because of their lower thermal conductivity, and the induced defects are found to play an important role in the thermoelectric transport properties. Here, we report the thermoelectric transport properties of single-crystalline ZrCoBi. Two samples from different batches clarify the same charge carrier concentration of ~1020 cm-3, denoting the robust Fermi level position in the ZrCoBi single crystals. The high electron density is attributed to the Zr interstitial point defects. Moreover, a high power factor of over 3.3 mWm-1K-2 is achieved in the single-crystalline ZrCoBi. By comparing the thermoelectric properties of single-crystalline and fine-grained polycrystalline samples, we reveal the role of grain boundary scattering in reducing the thermal conductivity from ~11.5 Wm-1K-1 to ~9 W/mK at 300 K. The present work declares the significance of defects in tuning the transport properties of ZrCoBi half-Heusler compound.

Учет разупрочнения вблизи свободной поверхности в прямой модели физической теории пластичности

Current industrial demands require the improvement of existing technologies and the creation of new ones that allow the production of parts and structures with advanced performance properties. Es-pecially important are the issues of design and analysis of thermomechanical treatment of metals and al-loys by intensive inelastic deformation methods. The study of manufacturing processes for miniaturized parts deserves special attention. The boundary value problems arising in this case belong to the class of physically and geometrically nonlinear problems of the mechanics of deformable solids, for the solution of which it is necessary to develop appropriate mathematical models. Most classical models are based on the macrophenomenological theory of elastoplasticity. However, in the processes under consideration, significant structural changes occur at the meso- and microscale that have a significant influence on the physical and mechanical characteristics of the processed materials and the performance characteristics of the products. These changes are not described by the mentioned theories. An effective approach to de-scribe these processes is to use multilevel models of crystal plasticity. Despite the tendency to miniaturize products, the parameters of such models are usually determined from the results of experiments on mac-rosamples. The question arises whether such parameters are valid for the analysis and modeling of real structures with typical length scales below 500 μm, where the internal and external boundaries of crystal-lites play a special role. In this study, the influence of the free surface on the mechanical properties of single crystalline and polycrystalline materials is considered. Modification of the basic direct crystal plas-ticity model of elastoviscoplasticity to account for the softening of slip systems near free boundaries due to easier exit of dislocations to the surface is proposed.

In silico study on probing atomistic insights into structural stability and tensile properties of Fe-doped hydroxyapatite single crystals

Hydroxyapatite (HA, Ca10PO4(OH)2) is a widely explored material in the experimental domain of biomaterials science, because of its resemblance with natural bone minerals. Specifically, in the bioceramic community, HA doped with multivalent cations (e.g., Mg2+, Fe2+, Sr2+, etc.) has been extensively investigated in the last few decades. Experimental research largely established the critical role of dopant content on mechanical and biocompatibility properties. The plethora of experimental measurements of mechanical response on doped HA is based on compression or indentation testing of polycrystalline materials. Such measurements, and more importantly the computational predictions of mechanical properties of single crystalline (doped) HA are scarce. On that premise, the present study aims to build atomistic models of Fe2+-doped HA with varying Fe content (10, 20, 30, and 40 mol%) and to explore their uniaxial tensile response, by means of molecular dynamics (MD) simulation. In the equilibrated unit cell structures, Ca(1) sites were found to be energetically favourable for Fe2+ substitution. The local distribution of Fe2+ ions significantly affects the atomic partial charge distribution and chemical symmetry surrounding the functional groups, and such signatures are found in the MD analyzed IR spectra. The significant decrease in the intensity of the IR bands found in the Fe-doped HA together with band splitting, because of the symmetry changes in the crystal structure. Another important objective of this work is to computationally predict the mechanical response of doped HA in their single crystal format. An interesting observation is that the elastic anisotropy of undoped HA was not compromised with Fe-doping. Tensile strength (TS) is systematically reduced in doped HA with Fe2+ dopant content and a decrease in TS with temperature can be attributed to the increased thermal agitation of atoms at elevated temperatures. The physics of the tensile response was rationalized in terms of the strain dependent changes in covalent/ionic bond framework (Ca–P distance, P–O bond strain, O–P–O angular strain, O–H bond distance). Further, the dynamic changes in covalent bond network were energetically analyzed by calculating the changes in O–H and P–O bond vibrational energy. Summarizing, the current work establishes our foundational understanding of the atomistic phenomena involved in the structural stability and tensile response of Fe-doped HA single crystals.

Competition of magnetocrystalline anisotropy of uranium layers and zigzag chains inUNi0.34Ge2single crystals

Structural and thermodynamic properties of single-crystalline ${\mathrm{UNi}}_{1\ensuremath{-}x}{\mathrm{Ge}}_{2}$ with $x=0.66$ have been investigated by measuring magnetization, specific heat, and thermal expansion over a wide range of temperatures and magnetic fields. The measurements revealed the emergence of a long-range antiferromagnetic ordering of uranium magnetic moments below the N\'eel temperature ${T}_{\mathrm{N}}=45.5(1)\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ and the existence of two easy axes in the studied compound, namely, $b$ and $c$, which correspond to the plane of the uranium zigzag chains. Magnetic field applied along these two crystallographic directions induces in the system a first-order metamagnetic phase transition (from antiferromagnetism to field-polarized paramagnetism), and the width of the magnetic hysteresis associated with that transition reaches as much as about 40 kOe at the lowest temperatures. A magnetic phase diagram developed from the experimental data showed that the metastable region associated with that magnetic hysteresis forms a funnel that narrows toward the N\'eel point in a zero magnetic field. The four-layer Ising model has successfully predicted the collinear antiferromagnetic structure in ${\mathrm{UNi}}_{0.34}{\mathrm{Ge}}_{2}$ (known from earlier reports), its magnetic phase diagram, and temperature and field variations of its magnetization. Moreover, it suggests that the first-order phase transition extends down to a zero magnetic field, although it is barely detectable in the experiments performed in low magnetic fields. According to this model, the second-order phase transition occurs in the compound only in a zero field.

Plant-mediated synthesis of NiO(II) from Lantana camara flowers: a study of photo-catalytic, electrochemical, and biological activities

In this study, nickel oxide nanoparticles (NiO NPs) were synthesized using Lantana camara flower extracts. Electrochemical (EIS and PDP) are conducted on the synthesized NiO NPs nanoparticles to show the corrosion inhibition efficiency. An XRD analysis showed that NiO-NPs generated a FCC structure that exhibited single-crystalline properties. SEM images showed particle size to be between 40 and 50 nm, which matched the average size determined from the XRD pattern. As compared to the reported spectrum, Fourier-transform infrared spectroscopy confirms the formation of NiO-NPs. A degradation study of Methylene blue (MB dye) photocatalytically showed up to 96–98%. Furthermore, the study reveals NiO-NPs possess antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Micrococcus luteus. These nanoparticles were made in a sustainable and cost-efficient manner. The research paves the way for future developments in the fields of biomedical applications.

Determination of Constitutive Parameters of Crystal Plasticity using Micro-pillar Testing with Pure Aluminum

The uniaxial compression test using the micrometer-sized specimen is employed to evaluate elastic-plastic deformation behavior of the selective single crystal from polycrystalline materials. Through reflecting these properties into the crystal plasticity finite element method (CPFEM), elastic-plastic analyses of the polycrystalline materials can be performed based on the single crystalline properties of real materials. In this study, the micro-pillar compression tests were conducted in the some single crystals of recrystallized polycrystalline pure aluminum. A method identifying CRSS, work hardening parameters and anisotropic elastic constants was proposed. The predicted stress-strain curves of single crystals obtained by CPFEM agree well with the original experimental data.

Influence of B Content on the Magnetostrictive Properties of Single-Crystalline, Poly-Crystalline, and Amorphous Fe-Co-B Alloy Films

Influence of B Content on the Magnetostrictive Properties of Single-Crystalline, Poly-Crystalline, and Amorphous Fe-Co-B Alloy Films

Resistive Switching Effects of Crystal‐Ion‐Slicing Fabricated LiNbO3 Single Crystalline Thin Film on Flexible Polyimide Substrate

AbstractThe fabrication process and resistive switching properties of flexible single crystalline LiNbO3 (LN) thin films are reported in this paper. Single crystalline LN thin films are transferred onto polyimide (PI) substrate by crystal‐ion‐slicing (CIS) technique using benzocyclobutene (BCB) as bonding layer. Low energy Ar+ irradiation is carried out to introduce a layer with high concentration oxygen vacancies. Uniform and stable resistive switching behaviors are observed in different memristor cells on the same thin film, which can be attributed to the single crystalline properties of the fabricated LN thin films. The on/off ratio is almost the same even when the LN thin film is bended either to different radii or thousand times. Thus, based on CIS technique and Ar+ irradiation, the fabrication method of flexible single crystalline thin films for flexible memristor is established. These results indicate that single crystalline LN thin film on PI substrate is a promising candidate structure for flexible memristor devices. A novel conduction model combined filamentary mechanism and Schottky emission mechanism is proposed to explain the resistive switching behavior.

Evidence of nontrivial Berry phase and Kondo physics in SmBi

Realization of semimetals with non-trivial topologies such as Dirac and Weyl semimetals, have provided a boost in the study of these quantum materials. Presence of electron correlation makes the system even more exotic due to enhanced scattering of charge carriers, Kondo screening etc. Here, we studied the electronic properties of single crystalline, SmBi employing varied state of the art bulk measurements. Magnetization data reveals two magnetic transitions; an antiferromagnetic order with a Neel temperature of ~ 9 K and a second magnetic transition at a lower temperature (= 7 K). The electrical resistivity data shows an upturn typical of a Kondo system and the estimated Kondo temperature is found to be close to the Neel temperature. High quality of the crystal enabled us to discover signature of quantum oscillation in the magnetization data even at low magnetic field. Using a Landau level fan diagram analysis, a non-trivial Berry phase is identified for a Fermi pocket revealing the topological character in this material. These results demonstrate an unique example of the Fermiology in the antiferromagnetic state and opens up a new paradigm to explore the Dirac fermion physics in correlated topological metal via interplay of Kondo interaction, topological order and magnetism.

Superelasticity and shape memory effect in zirconia nanoparticles

Superelasticity and shape memory effect are two key properties of zirconia-based ceramics which are mediated by the reversible tetragonal to monoclinic phase transformation. Although experimental studies discovered that the shape memory behavior of ceramics can be improved by reducing the grain boundary density, degradation in shape memory response still happens after a few cycles of loading–unloading–heating–cooling. In this work, superelastic and shape memory properties of single crystalline and polycrystalline yttria stabilized tetragonal zirconia (YSTZ) nanoparticles are studied by atomistic simulations. Fully recoverable superelastic strain (8.3%) is observed in a single crystalline nanoparticle by merely removing the compressive load. However, the shape memory behavior degrades with the increase of loading–unloading–heating–cooling cycles. In other words, a higher temperature is required for an additional strain recovery, but certain residual displacement may still remain after few cyclic loadings. Amorphous phase formation and its accumulation around the applied load contact area, as well as an increase in surface roughness are responsible for the observed degradation of shape memory response. In a polycrystalline YSTZ nanoparticle, besides the regular reverse transformation at the end of cyclic loading, most amorphous phase transfers back to the original tetragonal structure. However, a small amount of monoclinic phase is restrained by the permanent amorphous phase and grain boundaries at the end of cyclic loading, causing degradation of shape memory behavior.

Macroscopic properties of single-crystalline and polycrystalline graphene on soft substrate for transparent electrode applications

Large-area graphene synthesized by a chemical vapor deposition (CVD) method is promising for a flexible, stretchable transparent electrode but suffers from structural defects such as grain boundaries, which causes to degrade its physical properties. Recently, preparation methods of large-scale growth templates for single-crystalline graphene (SCG) were reported, but the macroscopic properties of SCG have not been adequately examined yet. Here, an SCG-based flexible, stretchable graphene transparent electrode is successfully demonstrated, which shows superior optoelectrical, electromechanical, and barrier properties compared to polycrystalline graphene (PCG)-based transparent electrodes. The result exhibits the grain boundary effect of graphene on soft substrates on a macroscopic scale and a great promise toward realizing a tremendous performance improvement of graphene-based flexible transparent electrodes on a large scale.

Effect of Single Crystallization on Thermoelectric Performance Improvement of Ba8CuxSi46−x Clathrate

The thermoelectric properties of single-crystalline and polycrystalline n-type Ba8CuxSi46−x type I clathrate were investigated and compared. Single-crystalline Ba8CuxSi46−x clathrate was synthesized by the Czochralski (CZ) method with a Cu content gradient, while spark plasma sintering (SPS) was used for the reorganization of polycrystalline materials. The same Cu content resulted in almost the same Seebeck coefficient in both single-crystalline and polycrystalline crystals, while the power factor $$ \left( {{\text{PF}} = S^{2} /\rho } \right) $$ of single-crystalline clathrate is twice that of polycrystalline clathrate. Thus, single crystallization is effective for the synthesis of high-efficiency thermoelectric materials in a type I Ba8CuxSi46−x clathrate ternary system.

Thermal conductivity of exfoliated and chemical vapor deposition-grown tin disulfide nanofilms: role of grain boundary conductance

Tin disulfide (SnS2) is a layered two-dimensional (2D) semiconductor material that shows great potentials in applications such as photodetectors, sensors, field-effect transistors, thermoelectric power generators, etc. The understanding of thermal transport in SnS2 is important for the optimization of thermal management and energy transport and conversion processes in these devices. Here we compare the in-plane thermal conductivities of mechanically exfoliated single-crystalline and chemical vapor deposition (CVD)-grown polycrystalline SnS2 nanofilms measured using the Raman optothermal technique. The polycrystalline SnS2 film with a grain size of 250 nm has a low in-plane thermal conductivity of 4.8–5.6 W m−1 K−1, which is approximately half that of the single-crystalline SnS2 film due to phonon scattering at the grain boundaries. The thermal transport across crystal grains is simulated using two approaches: (1) A finite element model with generated Voronoi cells, and (2) an empirical equation that takes into account the grain boundary thermal conductance (G′). The two approaches yield similar values for the effective G′, as well as consistent dependences of the in-plane thermal conductivity on the average grain size. It is predicted that the in-plane thermal conductivity of the polycrystalline SnS2 film can be substantially reduced with finer grains. The results of this work offer a fundamental understanding of the thermal transport properties of single-crystalline and polycrystalline SnS2 films from different growth methods, and demonstrate the potential to control the thermal conductivity of SnS2 by tuning the grain size for future thermoelectric applications.

Novel rhodamine probe for colorimetric and fluorescent detection of Fe3+ ions in aqueous media with cellular imaging.

A novel rhodamine-pyridine conjugated spectroscopic probe RhP was synthesized and its X-ray single crystalline properties were revealed with tabulation. The RhP displayed a distinct pale-pink colorimetric and "turn-on" fluorescent response to Fe3+ in aqueous media [H2O:DMSO (95:5, v/v)] than that of other interfering ions. During the Fe3+ recognition, the absorption (UV-Vis) and photoluminescence (PL) spectral studies revealed new peaks at 561 and 592nm, respectively. The 1:1 stoichiometry and binding sites were verified by Job's plot, ESI-mass, and 1H NMR titrations. Subsequently, LOD and binding constant for RhP+Fe3+ complex were estimated as 102.3nM and 6.265×104M-1 from linear fitting and Benesi-Hildebrand plots, correspondingly. Sensor reversibility of RhP+Fe3+ by EDTA was demonstrated by UV/PL and TRPL investigations. Moreover, the photoinduced energy transfer mechanism and band gap changes were established from the DFT interrogations. Lastly, cellular imaging studies were carried out to authenticate the real applicability of RhP in Fe3+ detection.

Stress Concentration Induced by the Crystal Orientation in the Transient-Liquid-Phase Bonded Joint of Single-Crystalline Ni3Al

Single-crystalline Ni3Al-based superalloys have been widely used in aviation, aerospace, and military fields because of their excellent mechanical properties, especially at extremely high temperatures. Usually, single-crystalline Ni3Al-based superalloys are welded together by a Ni3Al-based polycrystalline alloy via transient liquid phase (TLP) bonding. In this study, the elastic constants of single-crystalline Ni3Al were calculated via density functional theory (DFT) and the elastic modulus, shear modulus, and Poisson’s ratio of the polycrystalline Ni3Al were evaluated by the Voigt–Reuss approximation method. The results are in good agreement with previously reported experimental values. Based on the calculated mechanical properties of single-crystalline and polycrystalline Ni3Al, three-dimensional finite element analysis (FEA) was used to characterize the mechanical behavior of the TLP bonded joint of single-crystalline Ni3Al. The simulation results reveal obvious stress concentration in the joint because of the different states of crystal orientation between single crystals and polycrystals, which may induce failure in the polycrystalline Ni3Al and weaken the mechanical strength of the TLP bonded joint. Furthermore, results also show that the decrease in the elastic modulus of the intermediate layer (i.e., polycrystalline Ni3Al) can relieve the stress concentration and improve the mechanical strength in the TLP bonded joint.

Effect of Grain Sizes on Thermoelectric Properties of Extruded Samples of Bi0.5Sb1.5Te3 Solution

Electrical and thermal properties of single crystalline and extruded samples of a p-type Bi0.5Sb1.5Te3 solid solution with various grain sizes are studied in a wide temperature range of 80–300 K. It is revealed that the grain sizes significantly affect the values of the thermal-e. m. f. (α), electrical conductivity (σ), and thermal conductivity (χ) coefficients of the samples under study.

Magnetic impurity bands in Ga1−xMnxS : Towards understanding the anomalous spin-glass transition

We report on the magnetic and electronic properties of single-crystalline ${\mathrm{Ga}}_{0.91}{\mathrm{Mn}}_{0.09}\mathrm{S}$, which is a quasi-two-dimensional diluted magnetic semiconductor (DMS). Through an analysis of magnetization data, we show the existence of an anomalously high spin-glass transition temperature at 11.2 K. Using density functional theory (DFT), we characterize the properties contributing to the spin-glass transition through an examination of the electronic and magnetic properties for ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{S}$ with $x$ varying from 0.00 to 0.18 by randomly substituting Mn atoms into the gallium (Ga) lattice sites. We show that the presence of magnetic atoms produces impurity bands in the electronic structure, where an analysis of the density of states shows an increase in magnetic impurity bands at the Fermi level that lowers the semiconducting gap and is consistent with diluted magnetic semiconductors. Furthermore, this indicates that the spin-glass transition in ${\mathrm{Ga}}_{0.91}{\mathrm{Mn}}_{0.09}\mathrm{S}$ is similar to other DMS materials, where the primary mechanism is likely through magnetic exchange. However, the increased electron density in the system with Mn doping could explain the anomalously higher spin-glass transition temperature in ${\mathrm{Ga}}_{0.91}{\mathrm{Mn}}_{0.09}\mathrm{S}$. In comparison with the substantially lower transition temperatures in related II-VI based systems (i.e., ${\mathrm{Zn}}_{1\ensuremath{-}x}\mathrm{Mn}{}_{x}\mathrm{Te}$), the high transition temperature is associated with more metallic spin-glass systems that interact through RKKY exchange, which leads to the conclusion that there may be a combination of interactions occurring in these systems. Further measurements on the other substitution percentages will hopefully clarify these interactions.