Variation Of Lattice Constants Research Articles

Investigating coherent and semi-coherent interfacial structures and energetics in [formula omitted] interfaces: Theoretical insights into aluminum matrix composites bonding

Understanding the intricate interfacial structures and energetics between ceramics and aluminum is crucial for elucidating the mechanical properties of aluminum matrix composites (AMCs). However, previous theoretical simulations primarily focused on coherent interfaces, neglecting lattice constant variations on heterogeneous interfaces, which has led to discrepancies with experimentally observed semi-coherent interfaces. Here, using recently synthesized Al/Al3BC AMCs as a case study to systematically construct six semi-coherent interfacial models containing 383 to 588 atoms. These models are used to investigate the Al(11¯1)/Al3BC(0001) and Al(3¯11¯)/Al3BC(0001) structures and their associated energetics. Additionally, we examine 39 coherent interfaces for comparison. Work of adhesion and interfacial energy results reveal that the stable termination for semi-coherent interfaces is Al(B), which contrasts with AlC termination observed in coherent interfaces. Both Al(11¯1)/Al3BC(0001) and Al(3¯11¯)/Al3BC(0001) semi-coherent interfaces demonstrate higher stability but lower bonding strength compared to coherent interfaces. Bonding strength and stability of Al(B)-terminated semi-coherent interface in Al(3¯11¯)/Al3BC(0001) are lower than those in Al(11¯1)/Al3BC(0001). Electronic structure analysis indicates that AlC-terminated coherent interface exhibits greater charge transfer and stronger covalent metal bonds, while the Al(B)-terminated semi-coherent interface shows less charge transfer and more pronounced metallic bond characteristics. These computational insights provide valuable theoretical understanding of interfacial bonding mechanisms inherent in ceramic-reinforced AMCs.

Impact of Gd-substitution on structural, dielectric, spectroscopic, Raman, and photo luminance properties of Ba0.4Sr0.6Co2Fe16O27 ceramics

This paper represents a detailed study of Gd3+ substitutions on Structural, Dielectric, Spectroscopic, Raman, and Photo luminance Properties of Ba0.4Sr0.6Co2Fe16O27 magnetic oxides were prepared using the sol-gel auto combustion method. All of these specimens were sintered at 1100 °C for 5 h. X-ray diffraction analysis (XRD) confirmed the single-phase detection and structural analysis. The lattice parameters a and c show the insignificant behavior 5.893–5.933 Å, and 32.049–32.476 Å with the concentration of gadolinium ions. The crystallite size ranged from 25 to 30 nm, demonstrating a growing tendency as Gd-substitution was enhanced. The discrepancy in the ionic radii of iron (Fe3+) and substituent elements (Gd3+) is the cause of the variation in cell volume and lattice constants. FTIR spectroscopy confirmed the presence of absorption bands (590 and 3000 cm−1) for prepared BaSr-based W-type hexa-ferrites. The vibrational bands of metal oxide ions are responsible for the 590 and 685 cm−1 peaks. The Raman spectrum showed six discrete, brittle peaks: 320, 440, 620, 690, 1300, and 1600 of synthesized nanomaterials—the dielectric constant and dielectric loss increase by substituting the Gd3+ ion. The dielectric parameters and dielectric loss at higher frequencies suggest that the prepared material may be excellent for switching, sensing, and high-frequency applications.

A comprehensive first-principles investigation of structural, electronic, vibrational, optical, thermodynamic and thermoelectric properties of LiZnAs

The structural, electronic, vibrational, optical, thermodynamic and thermoelectric properties of Nowotny–Juza filled tetrahedral semiconductor LiZnAs under high pressure is investigated using the plane-wave pseudo-potential approach in the frame work of density functional theory (DFT) within the generalized gradient approximation (GGA). The calculated lattice constant (a0) and bulk modulus (B0) at ambient pressure are consistent with earlier reported experiment and theoretical results. The variation in Lattice constant, Bulk modulus (B0), Young modulus (Y), Shear modulus (G), Elastic anisotropy factor (A), Poission ratio (μ), Paugh (B/G) ratio and Elastic constants with pressure is analyzed and concluded. Electronic band structure calculations reveal that with applied pressure direct band gap increases and the indirect band gap decreases. Thermodynamic properties reveals thermodynamically stability with pressurize conditions. The real and imaginary parts of the Dielectric function (ε), Refractive index (η), Extinction Coefficient (k), Optical Conductivity (s), Electron/Optical Energy Loss Function (L), Absorption Coefficient (α), Reflectivity (R) at different pressure conditions are correspondingly studied. With applied pressure the absorption spectra shows a blue shift which makes LiZnAs as potential candidates for the application of optoelectronic devices in ultraviolet frequency range. The thermoelectric properties like Seebeck coefficient (S), Electrical conductivity (σ), and Electronic thermal conductivity (k) and Power factor (PF) have been studied as a function of temperature and chemical potential. Positive value of calculated Seebeck coefficient with temperatures ensures the p-type semiconducting nature of LiZnAs. Results provides theoretical guidance for future experimental investigations and industrial applications of LiZnAs.

An in-depth look at the structural, electronic, optical, and thermal properties of the cubic Be x Mg y Zn1−x−y O quaternary alloys

In the present research work, the structural, electrical, optical, and thermodynamic properties of the BexMgyZn1−x-yO quaternary alloy were investigated. Its conventional structure, which is composed of the binary compounds ZnO, BeO, and MgO, and their ordered ternary alloys BexZn1−xO, BexMg1−xO, and MgxZn1−xO are examined. A non-linear variation of lattice constants (a) and bulk modulus (B) as a function of the compositions (x, y) in BexMgyZn1−x-yO alloys is observed due to varying atomic radii of the constituent elements leading to the structural distortion against compositional changes. Both the ternary and quaternary alloys exhibit semiconducting properties, characterized by a direct bandgap ranging from 2–4 eV. This indicates their absorption and emission of light in the visible region of the spectrum, making them promising candidates for optoelectronic applications. The results of optical characteristics display the variation of refractive index and absorption coefficient of these alloys with respect to composition and wavelength. Present results will forecast the possible applications and guidelines for synthesizing such alloys under extreme conditions.

Organic-inorganic PTAA-SiGe transparent optical materials performance analysis for photo device applications

The SiGe materials has currently received a lot of interest due to its application for the advancement of optoelectronics and related sensor technologies. Its promising stability, and band gap-dependent performance for both bulk and nano-crystalline properties are vital as optical materials. To investigate the electrical performance of SiGe active materials based photo device, the spin coated organic p-materials contact is developed on sputtered SiGe on Quartz and ITO glass substrates. Both Si0.8Ge0.2 and Si0.9Ge0.1 films greater than 85 % visible band transparency are predicted that the deposited SiGe is nano-crystalline nature. It is also revealed from absorption-based band gap, AFM grain size and XRD analysis. The transmittance of SiGe thin film is increased with the microstrain of the films as a result, better opto-electrical performance is displayed. Ge composition though slightly makes variation of lattice constant and strain effect however, relatively lower transmittance films greater current density is exhibited. A higher rectifying ratio for lower transparent SiGe material deposited on ITO glass substrate is shown in the dark. Transparency and optoelectrical performance viewpoint white light illuminated PTAA/Si0.8Ge0.2 is shown better on Quartz substrate whereas the dark analysis PTAA/Si0.9Ge0.1 is realized more favorable on ITO glass substrate.

DFT calculations for electronic and magnetic properties of full Heusler Fe2MnAs alloy in perfect and defect structures

First-principles calculations within the framework of the density functional theory were conducted using the FP-LAPW method to investigate the electronic and magnetic properties of the Full-Heusler Fe2MnAs alloy. The study encompassed the examination of its perfect structure as well as the variation of lattice constants around the ground state. The negative value of the calculated formation energy suggests that the alloy may form spontaneously. From a magnetic perspective, Fe2MnAs exhibit a ferromagnetic order. The alloy also shows a high spin-polarization that may be increased, transforming the alloy into a half-metal, with the contraction of the lattice constant. Furthermore, the investigation delved into the effect of point defect formation. The calculated formation energies for vacancies, antisite, and exchange defects suggest the likely occurrence of some of these defects within the Fe2MnAs compound. Significantly, certain defects contribute to the spin-polarization of the alloy, effectively rendering it a fully half-metallic material.

First-principles investigation on structural, electronic, magnetic, mechanical and thermodynamic properties of half-metallic Zn-based all-d-metal equiatomic quaternary Heusler alloys

This study employs first-principles calculations based on density functional theory (DFT) to investigate the structural, electronic, magnetic, mechanical, and thermodynamic properties of Zn-based all-d-metal equiatomic quaternary Heusler alloys (EQHAs) XX'YZn (X = Fe, Ni, Co; X' = V, Cr; Y = Nb, Ti, Zr, Hf). The investigation encompasses three distinct structural types of all-d EQHAs, with the energy calculations revealing the Type-I configuration as the most stable. The electronic structure of the all-d EQHAs demonstrate 100% spin polarization. Specifically, NiVTiZn and NiVZrZn exhibit characteristics of half-metallic ferromagnets, while FeVNbZn, CoCrTiZn, CoCrZrZn, and CoCrHfZn manifest traits of half-metallic ferrimagnets. Notably, we have conducted computations concerning the magnetic properties of these six alloys, revealing that their principal magnetic moments stem from V and Cr atoms. This study analyzes the influence of lattice constant variations on the magnetic properties of the alloys and the width of the spin down energy gap. Results demonstrate that within the ranges of lattice constants from 5.6 Å to 6.4 Å for FeVNbZn, 5.5–6.6 Å for NiVTiZn, 5.8–6.8 Å for NiVZrZn, 5.8–6.7 Å for CoCrTiZn, 5.9–6.8 Å for CoCrZrZn and 6.0–6.9 Å for CoCrHfZn, these alloys maintain their stable half-metallic attributes. Furthermore, the investigated alloys demonstrate mechanical stability, exhibiting ductility and anisotropic characteristics. These investigations underscore the potential application prospects of half-metallic all-d EQHAs in spintronic devices.

Effect of Cr cations addition on the structural, morphological, optical, and photocatalytic properties of Er-doped ZnO structures

In this work, we have investigated the effect of Cr3+ cations addition on the structural, morphological, optical, and photocatalytic properties of Er-doped ZnO structures. The Zn(1-(x-y))ErxCryO compound, where [(x; y) = (0.00; 0.00), (0.02; 0.01), (0.02; 0.02) and (0.02; 0.03)] was synthesized by the co-precipitation method and thermally treated at 100 °C for 6 h. The structural study showed that the dopant cations concentrations, cause variations in lattice constants, and increase the crystallite size and the strain in the ZnO crystal lattice. The structural atomic disorder was confirmed by Raman and photoluminescence spectroscopies, with VO, VO+, and VO++ type oxygen vacancy defects dominating. The samples exhibited different morphologies depending on the dopant concentration (plates-like, irregular hemispherical particles, and octahedrons-like structures). In the photocatalytic test, the methylene blue (MB) dye degradation under UV irradiation increased as a function of Cr3+ cations concentration, achieving a degradation rate of 37.4 ± 1.9% for the sample containing 2% of Er3+ cations and 3% of Cr3+ cations. In addition, the MB dye removal capacity by the Zn(1-(x-y))ErxCryO compound was incremented to above 85% using an optimized H2O2 concentration. Finally, the irradiated solution did not show toxicity against Artemia salina, indicating that the intermediate photoproducts formed are not toxic.

Significant thermoelectric power and large magnetoresistance associated with elastic coupling in ternary PbBi2Te4

We present a detailed analysis of the structural and transport properties of PbBi2Te4 crystals. Thermal variations of lattice constants, as well as unit cell volume, follow a linear dependence but deviate from linearity around ∼ 100 K. The resistivity exhibits a semi-metallic character in its temperature dependence with a reasonably high magnetoresistance (MR) up to ∼ 90% at 2 K. The MR results comply with Kohler's rule, being a semi-classical two-band approach, when measurements are carried out below ∼ 100 K along the crystallographic c-axis, suggesting possible structural correlation. However, the MR results do not confirm to this rule when measured perpendicular to the c-axis. The absolute value of S is noteworthy, as it leads to a systematic increase with temperature to a thermoelectric power of ∼ 5 μW/cm-K2 at 300 K. To understand the Hall conductivities, we employ a two-band model that considers the interplay between electron and hole mobilities, as well as carrier densities. This interplay, in addition to the structural correlation, plays crucial roles in fine-tuning the MR and thermoelectric properties.

Behaviors of AlGaN Strain Relaxation on a GaN Porous Structure Studied with d-Spacing Crystal Lattice Analysis.

The high porosity of a GaN porous structure (PS) makes it mechanically semi-flexible and can shield against the stress from the thick growth template on an overgrown layer to control the lattice structure or composition within the overgrown layer. To understand this stress shield effect, we investigated the lattice constant variations among different growth layers in various samples of overgrown Al0.3Ga0.7N on GaN templates under different strain-relaxation conditions based on d-spacing crystal lattice analysis. The fabrication of a strain-damping PS in a GaN template shields against the stress from the thick GaN template on the GaN interlayer, which lies between the PS and the overgrown AlGaN layer, such that the stress counteraction of the AlGaN layer against the GaN interlayer can reduce the tensile strain in AlGaN and increase its critical thickness. If the GaN interlayer is thin, such that a strong AlGaN counteraction occurs, the increased critical thickness can become larger than the overgrown AlGaN thickness. In this situation, crack-free, thick AlGaN overgrowth is feasible.

Structural, optical, electrical and magnetic tuning based on Zn substitution at A site in yttrium doped spinel ferrites

The series of Zn2+ doped Co–Ni–Y spinel ferrites with compositional formula Co0.6Ni0.4-xZnxFe1.9Y0.1O4 where x = 0.0, 0.1, 0.2, 0.3, 0.4 were synthesized by chemical co-precipitation technique. Structural, optical, electrical and magnetic properties were explored by X-ray diffraction (XRD), Ultra violet spectroscopy (UV–Vis), Fourier transformation infrared spectroscopy (FTIR), four-point probes I–V technique and Vibrating sample magnetometer (VSM), respectively. Variations in lattice constants were detected with the insertion of Zn due to the difference in ionic radii of Zn2+ (0.82 Å) and Ni2+ (0.79 Å). FTIR outcomes exposed the existence of tetrahedral frequency absorption band in the range of 545.24–522.34 cm−1. Optical band gap energy (Eg) determined from the UV–Vis data was observed to be decreased from 3.86 to 1.84 eV. DC electrical resistivity of synthesized nanoferrites showed decreased nature in the range of 1.46 x 1010–7.78 x 107 Ω-cm for x = 0.0–0.4, respectively. Remarkable values of coercivity and microwave frequency signified that fabricated nanoferrites are highly applicable in high frequency switching devices.

Band alignment study at the SrTaO2N / H2O interface varying lattice constants and surface termination from first-principles calculations

In the search for new renewable energy to replace fossil fuels, Hydrogen is one of the most promising candidates for clean energy production. But cheap Hydrogen separation and storage is still a big challenge. Photoelectrochemical devices look promising for the decomposition of the water molecule into 2H2 + O2. Every day new materials and combinations are discovered or invented to improve the efficiency of the complex total process. A necessary condition for the photoelectrochemical process to work without a bias voltage is that the minimum of the semiconductor conduction band must be more positive than the reduction potential H+ to H2, whereas the maximum of the semiconductor valence band must be more negative than the oxidation potential of H2O to O2. Thus, band alignment studies in interfaces of semiconductors with water become of vital importance.In this work, first-principles calculations based on density–functional theory (DFT) in the all-electron and the pseudo-potential approaches have been performed for the analysis of the band alignment in SrTaO2N/H2O interfaces. Different surface orientations were analyzed, together with the dependence of the gap and band alignment with lattice constants for systems grown on mismatched substrates. Water structures were built from classical molecular dynamics and its electronic structure calculated using DFT. The calculations show that the SrTaO2N (001) is suitable for photoelectrochemical applications on a wide range of lattice constant a, except for a compression/elongation of −2%, −1% and 3%, while SrTaO2N (110) results suitable for photoelectrochemical devices over a wider range of lattice constants from −1% to 3%.

Atomistic simulations of dislocation plasticity in concentrated VCoNi medium entropy alloys: Effects of lattice distortion and short range order

Face-centered cubic (fcc) high and medium entropy alloys (H/MEAs) have been shown to display superior mechanical properties at low temperatures, but significant improvement of their strength at high temperatures is required for industrial applications at extreme conditions. Recently, it has been shown that the breakthrough of the MEAs from equiatomic/near-equiatomic to non-equiatomic ratios leads to strong MEAs with good ductility. To design new H/MEAs, we consider two important factors that may influence strength: the chemical composition and chemical short range order (CSRO). In this study, we investigate the depinning stress (σc) as a criterion of strength of several compositions of VCoNi concentrated solid solution alloys (CSSAs) including V0.33Co0.33Ni0.33, V0.35Co0.2Ni0.45, V0.33Co0.17Ni0.5, and V0.17Co0.33Ni0.5 at 5 K and 300 K, using atomistic simulations. The chosen interatomic potential is shown to be reliable by comparing experimental/ab initio values and calculated parameters such as lattice constant, shear modulus, depinning stress, and temperature variation of stacking fault width for equimolar VCoNi. We find a good agreement between experimental friction stress and the depinning stress extracted from our results for equimolar VCoNi. Also, we find that Vclusters are the main pinning points of dislocations, and With a random distribution of atoms, we find that the alloy composition V0.33Co0.17Ni0.5 displays the largest depinning stress at both 5 and 300 K. Furthermore, to investigate how CSRO affects the strength of these alloys, we design CSRO into the microstructure using two different methods: In the first method, hybrid Molecular-dynamics/Monte-Carlo simulations were employed to simulate annealing at various temperatures. We observe that such simulations create CSRO so that it increases with decreasing annealing temperature. Recently, the CSRO motif and its concentration in an equimolar VCoNi have been determined by experiment. By modeling this experiment, we also implemented the CSRO into microstructure as the second method. By using both methods, the effect of CSRO on the magnitude of the depinning stress is discussed. It was shown that in both methods, CSRO significantly influences the strength of non-equimolar VCoNi alloys.

Insight of structural, dielectric and spectroscopic characteristics of Ba0.6Sr0.4-xYbxFe12-yCoyO19 M-type hexaferrite

Ba0.6Sr0.4-xYbxFe12-yCoyO19, (0.0≤x ≤ 0.125, 0.0≤y ≤ 1.25) M-type hexaferrite were synthesized using the auto combustion sol-gel process. The synthesized samples were then sintered at 1200 °C for 5 h in a muffle furnace. XRD, FTIR, Raman, and Photoluminescence spectroscopies were used to analyse all the samples. XRD technique was used for structural examination of Ba0.6Sr0.4-xYbxFe12-yCoyO19. The XRD patterns of Yb–Co co-substituted M-type hexaferrites revealed the pure single phase of synthesized samples. Change in Yb–Co concentration influenced lattice parameters and unit cell volume. The variations in lattice constants "a" and "c" values are 5.891–5.862 and 23.180–23.317. FTIR spectroscopic data graphs revealed the formation of several absorption bands from 430 cm−1 to 3000 cm−1. The strain in the unit cell produced by substitution changes in Raman spectra which is also confirmed by XRD. Many 630 nm–700 nm emissions were observed in the PL spectra of Ba0.6Sr0.4-xYbxFe12-yCoyO19. Furthermore, a bandgap of 1.961–1.875 eV was observed for the pure sample. The substitution improves the dielectric losses and Ac conductivity. The Maxwell-Wagner theory was used to investigate the changing trends of characteristics regarding dielectric parameters. The findings show that the samples with the appropriate cationic substitution can be used in microwave and high-frequency applications.

Investigation of Boron Nitro Silicone Band Modulation Using the Tight-Binding Method

Boron Nitro silicon (Si2BN), as a 2D material, is used in a wide variety of applications due to its outstanding electrical properties. The electrical parameters of Si2BN need to be defined and engineered precisely to improve the device performance. This paper investigates the band structure and effective parameters of Si2BN using the tight binding approach. The unit cell including 4 atoms is considered for monolayer structure and the Schrodinger equation is calculated to obtain the energy levels. The effect of hopping energy on Si2BN band structure is also studied considering the conduction and valence bands. It is demonstrated that the distance between conduction and valance bands can be modified using the effect of lattice constant variation. The obtained results show that the nature of matter changes with fluctuating hopping energy of Si2BN. Alteration of the material properties can be explained in the form of applied perpendicular electric field to the Si2BN surface or strain and stress effects. The overlap energy variation in the form of band gap modulation is also explored and it is concluded that the band gap is decreased by strengthening of Silicon–Boron interaction. This research emphasized that obtained results are now suitable for being employed in different applications of nanoelectronics.

Effect of laser scanning speed on microstructure and mechanical properties of SLM porous Ti-5Al-5V-5Mo-3Cr-1Fe alloy

In this study, porous Ti-55531(Fe) was fabricated by selective laser melting (SLM) with different laser scanning speeds. The microstructures, surface morphology, inner defects, porosity, microhardness, and compressive behaviors were studied. The variation of lattice constant and hardness were analyzed. The results show that all the specimens have a density of ∼1 g/cm3, and a Vicker’s hardness with a range of 280–320 Hv0.1. The porosity of the SLM-produced materials is greater than the designed value (77%) and increases from 77.33% to 82.33% with the increase of laser scanning speed from 500 mm/s to 1,500 mm/s. Continuous irregular columnar dendrites, a large number of gas-induced defects with small size between 20 and 60 μm and a deep molten pool form in the specimens fabricated with a laser scanning speed less than 1,000 mm/s. Some defects, elongated voids and interrupted columnar dendrites are identified in the specimens fabricated with the laser scanning speed more than 1,000 mm/s caused by the insufficient input energy. All specimens with different laser scanning speeds show the single ß phase patterns. The compressive strength of the specimens with the laser scanning speed of 500 mm/s is maintained at 32 MPa and the compressive strength decreases with the increase of laser scanning speed. The specimens with a scanning speed of 500 mm/s present the best mechanical properties and surface quality.

Investigation of structural, optical and magnetic properties of Y3-xCexFe5-yEryO12 compound

Herein, we have studied the structural, optical and magnetic properties of Y3-xCexFe5-yEryO12 (0.00 ≤ x ≤ 0.02), (0.00 ≤ y ≤ 0.06) compound synthesized via sol gel process. Structural characterization by X-ray diffraction (XRD) confirmed the YIG single phase formation, belong to the Ia3‾d cubic centrosymmetric crystal structure. The lattice constant, lattice strain, dislocation density and average crystallite size variations were calculated and discussed in terms of the rare earth's dopant concentrations. Fourier Transform Infrared Spectroscopy (FTIR) analysis showed redshift for the Fe–O stretching modes as the dopant content increase, testifying the crystal lattice expansion. Raman spectra inspection corroborated the YIG single phase formation and shifts in the vibrational modes confirmed the Ce3+ and Er3+ rare earths inclusion in the sites occupied by Y3+ and Fe3+ cations, respectively. The coral-like of YIG nanoparticles were confirmed by scanning (SEM) and transmission (TEM) microscopies, whereas the existence of the elements Y, Fe, O, Ce and Er, were verified by Energy Dispersive Spectroscopy analysis (EDS). The optical band gap (Eg) decreases, while Urbach energy (Eu) increases varying the Er content. The result confirms the effect of Ce3+ and Er3+ addition on the optical properties of YIG, contributing to localized oxygen vacancy defects formation. Using a phenomenological model, it was shown that, the highest probability of Er3+ cations occupation corresponds to octahedral sites. For the Y2.98Ce0.02Fe5-yEryO12 (0.00 ≤ y ≤ 0.06) compound, the theoretical saturation magnetization (Ms) was calculated from the cation distribution obtained by the phenomenological model, resulting a slight increase with the Er content. The result agrees with the experimental Ms measurements, although for y = 0.06 a discrepancy was detected, which can be attributed to the breaking of collinear array of magnetic moments due to high lattice distortions.

Preparation and Investigation of Thermoelectric Properties of Cu3SbS4-Cu3SbSe4 Solid Solutions

Cu-based ternary chalcogenides composed of earth-abundant and nontoxic elements are considered promising thermoelectric materials, although there are few reports on them. In our previous studies, optimal mechanical alloying (MA) and hot pressing (HP) were used to synthesize Cu3SbS4 (famatinite) and Cu3SbSe4 (permingeatite). In this study, solid solutions of Cu3SbS4-ySey (y = 0–4) were prepared using MA and HP. X-ray diffraction and Rietveld refinement confirmed the formation of Cu3SbS4-Cu3SbSe4 solid solutions. The variation in lattice constants with Se content followed Vegard’s law. As the Se content increased, the carrier concentration and mobility increased. All the specimens exhibited p-type conduction, showing positive Hall and Seebeck coefficients. As the Se content increased, the Seebeck coefficient decreased due to an increase in carrier concentration, while the power factor of the solid solutions was not enhanced compared with that of the end compounds. Cu3SbS2.4Se1.6 exhibited the lowest lattice thermal conductivities of 0.84 Wm-1K-1 at 323 K and 0.56 Wm-1K-1 at 623 K because of phonon scattering (alloying scattering) caused by the formation of the solid solutions. In addition, the thermal conductivity was less than 0.8 Wm-1K-1 at 623 K. This was attributed to the phonon scattering (boundary scattering) caused by several grain boundaries introduced during MA. As the Se content increased, the dimensionless figure of merit gradually increased from 0.14 to 0.39 at 623 K.

Ruddlesden–Popper Faults in NdNiO3 Thin Films

The NdNiO3 (NNO) system has attracted a considerable amount of attention owing to the discovery of superconductivity in Nd0.8Sr0.2NiO2. In rare-earth nickelates, Ruddlesden–Popper (RP) faults play a significant role in functional properties, motivating our exploration of its microstructural characteristics and the electronic structure. Here, we employed aberration-corrected scanning transmission electron microscopy and spectroscopy to study a NdNiO3 film grown by layer-by-layer molecular beam epitaxy (MBE). We found RP faults with multiple configurations in high-angle annular dark-field images. Elemental intermixing occurs at the SrTiO3–NdNiO3 interface and in the RP fault regions. Quantitative analysis of the variation in lattice constants indicates that large strains exist around the substrate–film interface. We demonstrate that the Ni valence change around RP faults is related to a strain and structure variation. This work provides insights into the microstructure and electronic-structure modifications around RP faults in nickelates.

The Investigation of Lattice Properties for Group-IV Sigesn Ternary Alloy: By Using Machine Learning Method

Group-IV SiGeSn ternary alloy is a hot spot in the field of fabricating high-efficient Si-based light source due to its large lattice constant and bandgap variation range. However, due to the high cost and low speed of experimental and computational research, it is difficult to obtain their lattice constants comprehensively and quickly. Machine learning prediction based on statistics is an advanced method to solve this problem. In this paper, based on the existing data of group IV alloys, three machine learning methods such as Random Forest (RF), Support Vector Regression (SVR) and Gradient Boosting Decision Tree (GBDT) have been built to predict the lattice constants of SiGeSn. Firstly, the lattice constants of Group-IV alloys are collected to construct data set; Then, the data set are used to train the machine learning models which describe the quantitative relationship between concentrations and lattice constants; Finally, the prediction performance of these models are compared with each other, and the concentrations with appropriate lattice constants are predicted. The results show the comprehensive performance of SVR model is better than the other two, which means the SVR model can be used to directly predict the lattice constants of SiGeSn.