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Investigation of Structural and Elastic Stability, Electronic, Magnetic, Thermoelectric, Lattice-Dynamical and Thermodynamical Properties of Spin Gapless Semiconducting Heusler Alloy Zr2MnIn Using DFT Approach
摘要： In recent times, spin gapless semiconductors (SGS) have attracted much attention as a promising candidate for spintronics and thermoelectric applications due to their high carrier concentration and good thermoelectric figure of merit. In this paper, we have carried out a systematic theoretical investigation of the structural, elastic, thermal, electronic, magnetic, thermoelectric, lattice dynamical and thermodynamical properties of Zr2MnIn using density functional theory (DFT) based first principle calculations. The band structure calculation shows indirect band gap in a spin down channel and zero band gap in a spin up channel of valence and conduction bands confirming the spin gapless semiconducting nature of Zr2MnIn. The structural and dynamical stability of the antiferromagnetic phase of Zr2MnIn has also been investigated. Magnetization in Zr2MnIn originates due to the d state electrons of Zr atoms, which follows the Slater Pauling rule: Mt = Zt (cid:2) 18. Phonon dispersion curves exhibit real frequency of phonon modes throughout the Brillouin zone, which confirms the dynamical stability of the antiferromagnetic phase of Zr2MnIn. Thermodynamical properties including specific heat and Debye temperature have been calculated using phonon density of states. A higher value of the thermoelectric figure of merit 1.25, predicts that this alloy as good thermoelectric properties with better output efficiency.
关键词： Spin gapless semiconductor (SGS),magnetic moment,structural and elastic stability,thermoelectric and lattice dynamical properties,electronic structure
更新于2025-09-23 15:23:52
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Core-shell structure of ZnO/Co3O4 composites derived from bimetallic-organic frameworks with superior sensing performance for ethanol gas
摘要： In recent years, metal-organic frameworks (MOFs), especially zeolite-imidazole frameworks (ZIFs), have been attracting widespread attention as templates for the synthesis of sensing materials. Limited researches, however, have been carried out to utilize bimetallic ZIFs in gas sensing, as the existing studies mostly involve mono-metallic ZIFs. Here in, the core-shell structure of ZnO and Co3O4 composite (CS-ZnO/Co3O4) was synthesized via chemical etched to Co/Zn based zeolitic imidazolate framework (Co/Zn-ZIF) with subsequent annealing. The morphology, composition and surface characteristics of the as-obtained samples were confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET). Moreover, the gas sensing measurements were implemented under various atmospheres. The response of CS-ZnO/Co3O4 sensor to 100 ppm ethanol at 200 °C achieves 38.87, which is 2.8 times that of single-shell ZnO/Co3O4 (SS-ZnO/Co3O4). The improved response is mainly attributed to the core-shell structure, which offers larger surface area, more active sites for gas diffusion and the formation of p-n heterojunction between ZnO and Co3O4.
关键词： Bimetallic-organic framework,Core-shell structure,ZnO/Co3O4,Ethanol gas sensor
更新于2025-09-23 15:23:52
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Optical, magnetic and ferroelectric properties of Ba0.2Cu0.8-xLaxFe2O4 (x?=?0.2–0.6) nanoparticles
摘要： The Ba0.2Cu0.8-xLaxFe2O4 (x = 0.2, 0.4 & 0.6) (BCLF) nanoparticles were prepared by hydrothermal method and further characterized for structural, morphological, optical, magnetic, and ferroelectric properties. The structural analysis was carried out using X-ray diffraction spectra. These results revealed that all the samples showed the presence of cubic spinel phases. The Fourier transform infrared (FTIR) studies expressed the formation of broad (ν1) and narrow (ν2) absorption bands which can reflect the arrangement of cations between tetrahedral (ν1) and octahedral (ν2) sites. The surface morphology was studied using the field emission scanning and transmission electron microscopes (FESEM & TEM). The FESEM pictures expressed the gradual formation of nanofibers with increase of La-content. The variation of optical bandgap (Eg~1.96–2.15 eV) as a function of substituent concentration was elucidated. The magnetization versus applied magnetic field (M–H) loops of BCLF nanoparticles showed the superparamagnetic nature which can be useful for the biomedical applications. The cation distribution was made between the octahedral (B) and tetrahedral (A) sites using the Neel's two-sublattice model.
关键词： Nanoparticles,Structure,Optical properties,Rare Earth,Magnetic properties
更新于2025-09-23 15:23:52
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Structure variation and luminescence enhancement of BaLaMg(Sb, Nb)O6:Eu3+ double perovskite red phosphors based on composition modulation
摘要： A series of BaLaMgSb1-xNbxO6:Eu3+ double perovskite red phosphors was successfully obtained. X-ray diffraction and Rietveld refinement analyses were conducted to determine the phase information and the detailed structure parameters. The coordinate variations of both La3+/Eu3+ and Sb5+/Nb5+ were discussed to elucidate the influence of B-site ion doping on the lattice variation. Luminescence properties, excitation and emission spectra, were presented to show the advantages of doping with Nb5+ ion. Ultraviolet-vis diffuse reflectance spectra were performed to reveal the reason for the decreased emission intensity under the charge transfer band excitation. Moreover, band gap energy was estimated to clarify the relationship between the increased intensity (λex = 395 and 465 nm) and Nb5+ concentration. Intensity ratios of I(615)/I(590) were performed to show the symmetry variation of the lattice. Thermal quenching property was also investigated and the quenching mechanism was discussed in detail based on the ionization process.
关键词： White LED,Structure variation,Thermal quenching mechanism,Double perovskite
更新于2025-09-23 15:23:52
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First-principles study of the electronic structure and optical properties of Eu2+–M (M = Mn2+, Mg2+, Li+) co-doped γ-AlON phosphor
摘要： In our recent work we found γ-AlON:Eu2+ phosphors to hold promise for application in white light-emitting diodes (LEDs). To obtain further insight into Eu2+–M (M = Mn2+, Mg2+, Li+) co-doped γ-AlON, the crystal structure and the electronic and photoluminescence properties of γ-AlON:Eu2+–M (M = Mn2+, Mg2+, Li+) phosphors were studied using first-principle calculations under the framework of density functional theory. Based on the experimental and calculated results, the structure of Eu2+–M (M = Mn2+, Mg2+, Li+) co-doped γ-AlON was established. The calculated results demonstrate that Eu2+ and M (= Mn2+, Mg2+, Li+) can effectively improve the absorption of ultraviolet light by γ-AlON:Eu2+. The absorption coefficient of AlON:Eu2+–Li+ in the ultraviolet blue region of 275–415 nm reached 67,266 cm–1, and the absorption coefficients of AlON:Eu2+–Mn2+ and AlON: Eu2+–Mg2+ at the same doping concentration were 51,219 and 60,575 cm–1, respectively. Our calculations therefore show that the performance of AlON:Eu2+–Li+ is better than AlON:Eu2+–M (M = Mn2+, Mg2+).
关键词： γ-AlON,First principles,Electronic structure,Optical property
更新于2025-09-23 15:23:52
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A Novel Multilayer Sandwich Fabric-based Composite Material for Infrared Stealth and Super Thermal Insulation Protection
摘要： At present, infrared stealth materials for advanced detection and stealth technology is usually prepared with low emissivity coating on the surface, but there are very few efficient infrared stealth materials based on textiles with lightweight and flexible features. In this paper, we designed a carbon nanotube-doped aerogel (CNTAs) sandwich structure on polyimide (PI) fabric by hot pressing and then coated with a low emissivity Al-doped ZnO (ZAO) on the outer surface. The surface emissivity lower than 0.5 due to the existence of ZAO and the thermal conductivity of the intermediate interlayer aerogels as low as 0.013 W/(m?K). Additionally, through experiments, theoretical derivation and simulation analysis, we found the resultant composite demonstrated a high infrared stealth performance with super insulation effect, implying it will have a fine prospect in infrared stealth and thermal insulation protection fields with its unique structure and excellent properties.
关键词： Carbon Nanotube-doped Aerogel,Sandwich Structure,Infrared Stealth,Polyimide Fabric,Thermal Insulation,Al-doped ZnO
更新于2025-09-23 15:23:52
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Reduced order derivation of the two-dimensional band structure of a mixed-mode resonator array
摘要： In this paper, the 2D band structure of a mixed-mode metamaterial resonator array for in-plane waves is investigated. The band structure in the interior and on the boundary of the irreducible Brillouin zone and 1D dispersion diagrams for different propagation angles are calculated numerically and presented. Additionally, a reduced order analytical method is established to compare and approximate the band structure. The studied metamaterial, with a T-shaped cantilever beam as the resonator in its square array repeating unit cells, exhibits branches with mixed P and SV waves except at exactly one angle of propagation. This paper also reports on the occurrence of avoided level crossings, which are related to the existence of exceptional points in the complex domain. A reduced order analytical approach is used that can generate partial (low branches) band structure with relatively little computational effort. The reduced order model agrees well with the numerical results for these low branches and can provide support in mode identification and band sorting. With proper adjustments in parameters, this analytical method will be applicable to other metamaterials that have a similar unit cell structure.
关键词： band structure,reduced order model,resonator array,metamaterial,avoided level crossings,mixed-mode waves
更新于2025-09-23 15:23:52
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Growth, morphology and crystal structure of electrodeposited Bi2Se3 films: Influence of the substrate
摘要： In this study, we investigated the growth, morphology and crystal structure of electrodeposited Bi2Se3 films on n-Si, Au and Ru substrates. The range of potentials at which films with good quality and stoichiometry can be grown have been identified. Scanning electron micrographs of the early stages of nucleation and growth suggests the film formation on all three substrates follow the Volmer-Weber growth mode. In the case of Si substrate, a pure orthorhombic phase of Bi2Se3 could be grown which is influenced by the epitaxy of the Si substrate. The Faradaic efficiency of film growth on Si substrate was found to be around 90%. However, on Au and Ru substrates, growth of mainly the rhombohedral phase could be achieved having relatively lower Faradaic efficiencies of 68% and 78%, respectively. The Bi2Se3 films grown on Au at more negative potentials were found to exhibit improvements in the rhombohedral crystal phase. Low temperature annealing was found to transform the orthorhombic or mixed phase crystal structure to that of pure rhombohedral. The onset of phase transformation in the mixed phase Bi2Se3 films (on Au) was found to be around 125°C, determined using in-situ Raman spectroscopy. Aside from the temperature, the duration of heat treatment is identified to play a crucial role in this phase transformation. Based on our findings on room temperature deposition, we conclude that the growth of pure orthorhombic phase is favored on Si, while on Au and Ru, growth of the rhombohedral or mixed phase of Bi2Se3 could be achieved.
关键词： Raman,Annealing,Electrodeposition,Crystal structure,Substrate epitaxy,Bi2Se3,Growth
更新于2025-09-23 15:23:52
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Multi-active sites derived from a single/double perovskite hybrid for highly efficient water oxidation
摘要： The oxygen evolution reaction (OER) plays a crucial role in the application of water splitting, which is a highly competitive option for a sustainable energy future. Thus, it is vital to design highly active and durable electrocatalyst for OER. Herein a hybrid with the nominal composition of Ba2Co1.5Mo0.25Nb0.25O6-d (denoted as BC1.5MN) electrocatalyst consisting of both double perovskite and single perovskite structures is synthesized by a solid-state reaction method. When tested as an electrocatalyst for OER, the BC1.5MN electrocatalyst requires a current density of 10 mA cm-2 at an overpotential of 400 mV, an onset overpotential of 260 mV, and a Tafel slope of 70 mV dec-1, which are superior to that of precious metal oxide IrO2 catalyst. Chronoamperometric and cyclic voltammetry studies demonstrate that the BC1.5MN electrocatalyst has outstanding durability in alkaline solution. The synergistic effect between multi-active sites derived from a single/double perovskite hybrid structure results in one of the most active perovskite-based OER electrocatalysts in alkaline solution.
关键词： hybrid,oxygen evolution reaction,double perovskite,single perovskite,electronic structure
更新于2025-09-23 15:23:52
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Backward wave oscillation suppression study of the helix travelling wave tube
摘要： In this paper, the effect of backward wave oscillation (BWO) on helix slow wave structure performance for TWT has been described. In this paper both the cases tapered and untapered helix slow wave structure (SWS) have been analyzed, caused by BWO for high gain helix TWT. In house developed the one-dimensional (SUNRAY-1D) large signal analysis model has been used for stability analysis of the helix SWS. The analysis on backward wave amplifier gain has been carried out as a function of the taper parameter and frequency parameter. The position and nature of tapering also affect the electronic efficiency as well as the start oscillation current. Hence, position and nature of tapering have been optimized.
关键词： backward wave oscillation (BWO),support rods,instability,Slow wave structure (SWS)
更新于2025-09-23 15:23:52