查看更多>>摘要：? 2022 Elsevier B.V.The present research is conducted to investigate the effect of Au coating on the physical properties of the nanostructured Bi2S3 for optoelectronics applications. The Bi2S3 films are deposited using the chemical vapor deposition (CVD) at three different temperatures. The structural analysis shows the formation of polycrystalline orthorhombic Bi2S3 films and Bi-rich composition. In addition, the morphological studies indicate dense and compact films with nanorod-like morphology on the surface. Optical evolution of Bi2S3 films demonstrates an increase in the optical energy band gap (Eg) once the deposition temperature increases. Moreover, the addition of Au coating increases the absorption intensity and Eg of the samples in comparison with the Free-coated samples. The Mott-Schottky analysis indicates the highest carrier concentration amount (7.67 ×10+18 cm?3) for the Au-coated samples which are deposited at 420 °C. The photodetector characteristics of the fabricated p-Si/n-Bi2S3 heterojunction devices show meaningful improvement in the quality parameters (QPs), including gain (G) and sensitivity (S). The charge transportation mechanism of the devices is discussed in detail calculating ideality factor (n), carrier mobility (μ), and trap-filled limited potential (VTFL).
查看更多>>摘要：? 2022 Elsevier B.V.Based on characteristic multielectron conversion reactions, transition-metal oxides are regarded as potential anode candidates for the new generation of lithium-ion batteries (LIBs) because they are endowed with high specific capacity. Nevertheless, the inferior electronic conductivity and larger volume change lead to fast capacity decay during cycling. Herein, we propose a novel electrophoretic deposition strategy to prepare binder-free Mn3O4/graphene hybrid electrodes and overcome these two obstacles simultaneously. In the rationally designed structure, Mn3O4 nanoparticles are well encapsulated in the conductive network constructed by interconnected graphene sheets. In the process of cycling, thanks to the excellent flexibility of graphene and the rich voids in this sandwiched structure, not only the structural integrity but also the unobstructed conductive network can be ensured. In addition, it is verified that electrode kinetics is a fast process for surface-controlled lithium storage. From this perspective, in addition to high reversible specific capacity (880 mAh g?1 at 0.1 A g?1), the prepared Mn3O4/graphene hybrid electrode possesses outstanding rate capability (678 mAh g?1 at 5 A g?1) and remarkable cycling stability (neglectable capacity decay after 500 cycles at 1 A g?1).
查看更多>>摘要：? 2022 Elsevier B.V.Obtaining detailed transmission and transition parameters of transparent materials is of vital importance for photonic engineering applications. In this work, we prepare a series of lanthanide active ions (Ln, Ln = Nd, Sm, Dy, Ho, Er, Tm) doped Y2Zr2O7 (YZO) transparent ceramics through solid-state reaction method without any sintering aids, and its transmittance is very close to the theoretical limit. The Ln activator doping dependent refractive index, Abbe number, and theoretical transmission are investigated detailedly. Besides, the J-O intensity parameters Ωi (i = 2, 4, 6) of the prepared transparent YZO:Ln ceramics are obtained using J-O theory, and we elaborate on how the corresponding factors determine the variation of these parameters. Furthermore, combining theoretical calculations and spectroscopy characterization, this work provides a valuable reference of spectroscopic properties, such as spontaneous transition probabilities, radiation lifetime, and fluorescence branch ratio, in transparent lanthanide zirconate ceramics.
查看更多>>摘要：? 2022 Elsevier B.V.The correlation between the generalized stacking fault energy and the strengthening mechanisms of Cr–Fe–Co–Ni high-entropy alloys during uniaxial tensile deformation is investigated using molecular dynamics simulations. An increase in the Cr and Fe content decreases the generalized stacking fault energy, while an opposite trend is observed for the content of Co and Ni. A linear correlation is identified between the unstable stacking fault energy and the yield stress. Alloys with a lower Fe content and higher Co and Ni contents show a higher unstable stacking fault energy, and hence higher yield stress. A high density of Lomer–Cottrell locks or deformation twins leads to higher flow stress. The deformation twins play a more important role in enhancing the flow stress as compared to sessile dislocations. Additionally, high unstable stacking fault energy is required to stabilize the defects formed and contribute to increasing flow stress. For a low unstable stacking fault energy, the plastic deformation progresses at lower stress and a bidirectional defect transformation is observed. The results agree with recent experiments and serve as guidelines for how the composition can be used to enhance the yield strength and the efficiency of strengthening mechanisms in Cr–Fe–Co–Ni high-entropy alloys.
查看更多>>摘要：? 2022 Elsevier B.V.The present work deals with synthesis and optical properties of NaGdMgTeO6: x% Eu3+ (x = 2%, 4%, 6%, 8%, 10%, 12%, and 14%) double layered perovskite phosphors synthesized via conventional solid state ceramic route. X-ray diffraction profile along with Rietveld refinement reveals the single phase nature of the compounds. Further Raman and FTIR spectroscopy were carried out to deduce the structural modifications induced by the substitution of Eu3+ ions at Gd3+ site. A direct bandgap of 3.5 eV suggests that these phosphors can be efficiently excited using ultraviolet radiation. The compound can be efficiently excited by 265 nm and gives red emission at 615 nm corresponding to 5D0- 7F2 electric dipole transition of Eu3+ ions. The optimum doping concentration of Eu3+ is obtained as 8 mol% beyond which concentration quenching occurs. Thermal activation energy of the phosphor is evaluated as 0.2 eV. Thermal stability and other phosphor parameters show its potential application in solid state lighting. The relative temperature sensitivity and absolute sensitivity obtained by measuring fluorescence intensity ratio of 5D0→ 7F1 to 5D0→7F2 is 0.23%K-1 and 0.0072 K?1 respectively. Judd-Ofelt parameters were evaluated which are in good agreement with the results obtained from PL spectra. Judd-Ofelt theory is further extended to evaluate thermometric parameters by considering the emissions from 5D0 and 5D1 thermally coupled energy levels (TCLs) of Eu3+ ions. A good match is observed between thermometric parameters obtained by conventional method and Judd-Ofelt theoretical model. All the results suggested that NaGdMgTeO6: Eu3+ phosphors have potential applications in solid state lighting and optical thermometry.
查看更多>>摘要：? 2022 Elsevier B.V.The Ni–Mn–based shape memory alloys as a promising candidate of elastocaloric material has been reported in many literatures, especially on bulk samples. The as-spun ribbon, which has a larger surface area and is more efficient for heat transfer, is rarely studied and hence of importance. In the present work, we succeeded in producing very long as-spun Ni–Fe–Mn–(Al, In) ribbons, with around 300 mm in length. The microstructure and mechanical properties of these as-spun ribbons were thoroughly investigated by scanning electron microscopy and electron backscattered diffraction (SEM-EBSD), nanoindentation and 3-points bending experiments. Through SEM-EBSD analyses, the microstructure and texture of the as-spun ribbons were studied. A gradient in microstructure exists along the thickness direction (TD) of the ribbon, which is induced by the temperature gradient during fast rate solidification, resulting in fine equiaxed grains along the surface contacted with the rotating wheel in melt spinning process and elongated grains, respectively. Both equiaxed and elongated grains possess a strong {001} fiber texture (<001>//TD). Nanoindentation analyses show little variation of hardness between the two different microstructures. The ductility index of both Ni–Fe–Mn–Al and Ni–Fe–Mn–In ribbons are within the range of intermetallic materials. The substitution of In by Al allows to increase very slightly the ductility index, which can reach 0.75. The fine equiaxed grains show better tensile resistance than the elongated grains in 3-points bending test. The substitution of In by Al improves the maximum bending strain by a factor of 3. The maximum strain for Ni–Fe–Mn–Al as-spun ribbons can reach 3% before fracture. Fractography shows that, the intergranular fracture is the main damage mechanism in these as-spun ribbons.
查看更多>>摘要：? 2022 Elsevier B.V.In this work, the temperature-induced phase transition of (Pb0.99Nb0.02)[(Zr0.70Sn0.30)1-xTix]0.98O3 (PNZST) ceramics near the morphotropic phase boundary (MPB) was investigated systematically. Increasing Ti content will stabilize the ferroelectric (FE) phase and destabilize the antiferroelectric (AFE) phase in PNZST ceramics, resulting a switching from AFE to FE. When x = 0.06, the composition has an initial AFE phase and can be induced into a stable FE phase at external electric field and when x = 0.08, the composition is normal FE. With increasing temperature, the poled PNZST sample (x = 0.06 and 0.08) will experience a ferroelectric-antiferroelectric-paraelectric (FE-AFE-PE) transition. The increasing Ti content will result in higher FE-AFE transition temperature. A step “0–1” voltage signal up to 90 V and a current pulse can be achieved in a specific circuit when the poled ceramics were heated. An electric energy of 13.7 mJ/cm3 was obtained during the heating process. And when the composition is closer to the AFE/FE boundary (x = 0.06), the voltage step signal is steeper because the charge release is more intensive. The special output electrical signal makes the PNZST ceramics near the MPB with potential applications for temperature sensor, temperature-controlled switch and temperature-driven pulsed power source. The phase transition properties can be further modified by modify the compositions near the MPB to satisfy different applications.
查看更多>>摘要：? 2022 Elsevier B.V.Ferroelectric perovskites are favored for integrated device applications due to their high dielectric constants and strong piezoelectric responses. However, the commonly used lead zirconate titanate system has disadvantages such as toxicity, current leakage, and fatigue. As an alternate lead-free material, this study examines the strain-induced ferroelectric properties of Bi3TaTiO9 (BTTO) thin films. BTTO thin films grown on single crystal Rh and Nb-doped SrTiO3 (Nb:STO) substrates via a pulsed laser deposition were compared. The Rh substrate has induced compressive stress in the BTTO thin film, whereas the Nb:STO substrate has induced tensile stress in the BTTO thin film. The BTTO thin film grown on the Rh substrate displayed a highly a-oriented crystallinity compared with the Nb:STO substrate. Significantly, the BTTO thin film on the Rh substrate exhibited improved ferroelectric properties, such as stronger hysteretic behavior, faster polarization switching, and higher piezoelectric coefficients. The surface morphologies and ferroelectric domains of the BTTO thin films were investigated via atomic force microscopy and piezoelectric force microscopy. Our findings provide insights into strain-engineered ferroelectric thin films and their potential device applications.
查看更多>>摘要：? 2022 Elsevier B.V.FeOOH has emerged as an attractive anode material for Li-ion batteries (LIBs) owing to its low cost and high capacity. However, the inferior electronic conductivity and poor structural stability of FeOOH impede its practical applications. To address these issues, novel hybrids of fluorine-doped FeOOH nanorods/reduced graphene oxide (F-FeOOH NRs/rGO) were synthesized via a simple one-step hydrothermal method. F-FeOOH NRs were grown in situ simultaneously with the reduction of graphene oxide, resulting in strong interfacial coupling of F-FeOOH with rGO. Benefitting from the synergetic effect of rGO and F-doping, the optimized F-FeOOH NRs/rGO hybrid presents a stable capacity of 1207.4 mAh g?1 at the 160th cycle at 0.1 A g?1 and a remarkable rate capability of 777.5 mAh g?1 at 2 A g?1. Furthermore, even after 400 cycles at 1 A g?1, a reversible capacity of 701.4 mAh g?1 can still be maintained. With simple synthesis method and excellent Li-storage performance, the F-FeOOH NRs/rGO hybrid is expected to be a prospective material for LIB anode.
查看更多>>摘要：? 2022 Elsevier B.V.The current paper reports the thermal annealing induced amorphous to crystalline transformation of the quaternary In15Sb10S15Se60 thin films prepared by the thermal evaporation method on glass substrate. The prepared films were annealed at 100 °C, 150 °C, 200 °C, and 250 °C under vacuum conditions. The structural characterization was done by X-ray diffraction and Raman spectroscopy which revealed the amorphous to crystalline transformation and the formation of different phases for the annealed films. The composition of the films was verified by Energy dispersive X-ray analysis, whereas the surface morphology pictures were taken by field emission scanning electron microscopy and atomic force microscope. The changes in both linear and nonlinear optical properties of as-prepared and annealed films were studied from UV-Vis spectroscopy data and related empirical formula. The significant reduction in transmission (55–4%) and shifting of absorption edge due to annealing resulted in the decrease of optical bandgap (from 1.641 eV to 1.301 eV) and increase in linear refractive index. The 3rd order nonlinear susceptibility (9.83 ×10?15 to 2.44 ×10?11 esu) and nonlinear refractive index (4.59 ×10?13 to 6.01 ×10?10 esu) were found to be increased due to more polarization effect. The role of annealing temperatures on the variation of different parameters was elaborately explained on the basis of amorphous to crystalline transition and defect states in the localized region. Based on the observed changes in the linear and nonlinear optical parameters by thermal annealing, the In15Sb10S15Se60 thin films could be a suitable candidate for numerous photonic and optoelectronic applications.
NSTL
Elsevier