Skipetrov, E. P.Bogdanov, E., VKovalev, B. B.Skipetrova, L. A....
7页
查看更多>>摘要：We synthesize a single-crystal Pb1-x-ySnxScyTe ingot and investigate the magnetic properties (2.0 <= T <= 300 K, B <= 3 T) of alloys cut from it (x = 0.045-0.175, y <_ 0.04). At low temperatures, all samples exhibit paramagnetic contribution to the magnetization, which contradicts the generally accepted model of doping-induced rearrangement of the electronic structure of alloys and is most likely due to the paramagnetism of electrically neutral Sc2+ ions or their clusters. In p-type samples, a high-temperature ferromagnetic ordering with a Curie temperature as high as T-C = 145-150 K is found, presumably due to the RKKY hole-mediated interaction of Sc2+ ions. We obtain dependences of the concentration of paramagnetic ions, of the paramagnetic Curie-Weiss temperature Theta and of the Curie temperature T-C on the concentrations of scandium and tin. At temperatures T < 100 K, the spin-glass-like behavior of magnetization and ferromagnetic hysteresis loops in the field dependences of magnetization are detected, indicating the formation of a mixed ferromagnetic-spin glass phase. (C) 2021 Elsevier B.V. All rights reserved.
Bhamu, K. C.Kang, Sung GuKushwaha, A. K.Rai, D. P....
10页
查看更多>>摘要：We report the structural, mechanical, electronic, optical, thermoelectric properties and spectroscopic limited maximum efficiency (SLME) of oxide double perovskite structure Ba2SbNbO6 and Ba2SbTaO6 compounds. All the investigations were performed through the first-principles density functional theory (DFT). The results obtained for the elastic constants affirms the mechanical stability of the studied double perovskite compounds. The calculated data of bulk modulus (B), shear modulus (G), and Young's modulus (E) for Ba2SbTaO6 are found to be greater than those of Ba2SbNbO6. The obtained ratio of Bulk to shear modulus (B/G) shows that Ba2SbNbO6 and Ba2SbTaO6 are ductile in nature and are suitable for the device fabrications. The electronic properties of studied compounds are explained in terms of their energy bands, total and partial density of states. The computed electronic band structure reveals the direct band gap semiconducting nature of both compounds. The energy dependent optical properties such as, dielectric tensor, optical conductivity, absorption, reflectivity, refraction and energy loss for both the studied compounds are investigated and are explained in order to highlight the potential of studied compounds for the photovoltaic applications. In addition to electronic and optical properties, we have also studied the electron relaxation time-dependent thermoelectric properties, such as Seebeck coefficient, electronic thermal conductivity, electrical conductivity, thermoelectric power factor, and the thermoelectric figure of merit as a function of chemical potential at various temperatures for p-type and n-type charge carriers. The high absorption spectra and good thermoelectric figure of merit reveal that both the studied compounds, Ba2SbXO6 (X = Nb, Ta) are promising materials for photovoltaic and thermoelectric applications. The calculated SLME of 26.8% reveals that Ba2SbNbO6 is an appealing candidate for single-junction solar cells. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Mechanoluminescence (ML) materials exhibit great potential in the fields of light sources, displays, and stress sensors because they can convert mechanical stimuli into luminescence. Most ML materials exhibit weak brightness and limited colors; therefore, tunable colors are highly desired. Herein, a facile strategy for tuning the ML of a flexible composite of zinc sulfide (ZnS) phosphor and all-inorganic CsPbX3 (X = Cl, Br, and I) perovskite quantum dots (PeQDs) is demonstrated. A broad color expression with a narrow emission band was achieved under low stretching-releasing stress by changing the halide component of CsPbX3. The color conversion between ZnS and PeQDs is a radiative combination and reabsorption process, and full color tuning from 510 to 710 nm occurred because of the bandgap tailoring of PeQDs. Furthermore, some proof-of concept devices, including multicolor displays and white light sources, were demonstrated by changing the composition of PeQDs. This work provides a versatile approach to fine-tune the ML spectrum, thereby paving the way for applications such as piezophotonic displays and white light sources. (C) 2021 Published by Elsevier B.V.
查看更多>>摘要：Herein, to investigate the photodegradation of methylene blue (MB) under UV light irradiation and the photocatalytic activity of chemically derived ZnO, ZnO: Co 5% nano rod-like thin films and ZnO/ZnO: Co 5% homojunction, the role of grain size and microstrain on their structural, optical, electrical and photocatalytic properties were studied. Hexagonal wurtzite structure, the doping of Co2+ into ZnO host lattice, reduced crystallite/grain size, and enhanced microstrain have been confirmed by structural and morphological analysis. The presence and the atomic content of Zn/Zn2+, Co/Co2+, O/O2- elements, and ions have been confirmed by EDS and XPS measurements. The n/p-type conductivity in nano rod-like film and p-n bilayers have been verified by Hall and I-V characterizations. The PL analysis showed that the decreased luminescence intensity and the formation of defect/trapping centers by Co2+ doping and formation of p-n homojunction as crystallite/grain size decreased while microstrain increased. With 5% Co-doping and the emergence of p-n homojunction, the photocatalytic efficiency (eta %) was reduced compared with parent ZnO photocatalyst, while the crystallite/grain size decreases and microstrain enhances. The decreased eta % was attributed to the reduced crystallite/grain size, increment of microstrain, and the generation of defects/ trapping centers via 5% Co-doing and formation of ZnO/ZnO:Co 5% nano rod-like homojunction. These results demonstrate that the fabrication of p-n homojunction will not always result in an enhanced eta % even if it puts down the recombination of light-induced charge transporters. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Transition metal oxides (TMOs) are deemed as promising next-generation anode materials for alkali-ion batteries owing to their high energy density. However, the structures of the TMOs electrode materials are destroyed due to the huge volume changes during charging/discharging, so that the batteries cannot pro -vide a long cycle life. Herein, a unique hierarchical MnMoO4@nitrogen-doped carbon (MnMoO4@NC) core-shell microspheres are synthesized as an advanced electrode material for lithium-ion batteries (LIBs) and potassium-ion batteries (PIBs). Specifically, the semi-hollow microspheres structures of MnMoO4 formed by self-assembly of nanoparticles can improve its utilization efficiency and the speed of ion transfer. Moreover, the uniform nitrogen-doped carbon layer not only improves the structural stability of MnMoO4 but also enhances the electrical conductivity of the overall composite. The resultant MnMoO4@NC as an anode for LIBs delivers 817 mAh g(-1) after 800 cycles at 1 A g(-1), and for PIBs remains 95 mAh g(-1) over 400 cycles at 0.5 A g(-1). (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：In this paper, preparation of long afterglow phosphor with different emission colors in the system Zn2SiO4:Eu3+, Dy3+, Mn2+ was done via melt-quenching technique. The effect of adding mono-di-and tridopant on the phosphorescence properties was studied. Also, the effect of applying different heat treatment programs on the appearance of glass-ceramic (GC) to get transparent or opaque materials were optimized. DTA, XRD, SEM, UV-visible NIR, and fluorescence spectrophotometer were used to characterize the obtained materials. The results revealed crystallization of willemite and zinc borate; both Mn and Dy addition enhanced the degree of crystallization while Eu depressed it. Heat treatment at 650 degrees C/5 h revealed transparent glass-ceramic (TGC), above this temperature opaque glass-ceramic was appeared. Calculation of optical band gap (E-opt), Urbagh energy (Delta E) and refractive index were located in the range: 2.1-2.8 eV, 0.53-0.79 eV and 2.45-2.64 respectively. Lifetime decay was increased by increasing heat treatment temperature; it reaches similar to 2 h after irradiation at 260 nm for 30 min giving green emission at 558 nm. Visual appearance for the emitting light varies from white, red, yellow to blue color. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Herein, bimetal nickel-cobalt phosphate (NiCoP) nanostructures coated on nickel foam (NF) were synthesized for hybrid supercapacitors by a facile one-step potentiostatic electrodeposition method. The optimization of the capacitive performance for supercapacitors was achieved by varying the deposition time from 5 to 20 min. When the electrodeposition time was 15 min, an optimal performance with the NiCoP/NF2 was achieved. A specific capacity of 883 C.g(-1) was recorded at a current density of 1 A.g(-1), a best rate performance of 87% along with a highest coulombic efficiency of 100%, revealing good capacitive performance and excellent reversibility. Furthermore, NiCoP/NF-2 was assessed as a positive electrode in a hybrid supercapacitor. Using activated carbon (AC) as a negative electrode, the assembled device exhibited an energy density of 54 Wh.kg(-1) at a power density of 2.7 kW.kg(-1) with a large working potential window of 0-1.8 V. After charging to 3.6 V for 19 s, two hybrid supercapacitor devices connected in series could light up a red LED for 191 s, which indicates that the proposed electrodeposition synthesis process and the prepared NiCoP composites hold high potential for applications in the field of energy storage technology. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：The growth of CdO-In2O3 amorphous oxide semiconductor alloys with high mobility in a wide composition range, suitable for many optoelectronic applications, has been previously reported using room temperature sputtering. In the present work, we synthesized Cd1-xInxO1+delta alloy thin films across the entire composition range using the non-vacuum, low-cost sol-gel spin coating method. Structural, electrical and optical properties of these alloy films were studied using a variety of analytical tools. We find that the alloy films become amorphous within the In composition range of 0.2 < x < 0.7, while films with x < 0.2 and x > 0.7 have the rocksalt CdO and bixbyite In2O3 structure, respectively. As-grown amorphous alloys have resistivity in the ranging from high 10(-3) to low 10(-2) Omega-cm due to their relatively low mobility of < 10 cm(2)/Vs. Electrical properties of these amorphous films are improved after annealing at similar to 400 degrees C with a mobility of similar to 10 cm(2)/Vs and a low resistivity in the low 10-3 Omega-cm range. The optical gap varies from 2.54 to 3.52 eV with increasing In mole fraction, so that transmittance > 85% over a wide transmission window of similar to 400-1600 nm can be achieved. The low temperature, low-cost non-vacuum processing, wide bandgap tunability, and low resistivity, make these sol-gel alloy films promising materials for optoelectronic applications, especially on organic layers and/or flexible substrates. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：In this work, we study the effect of sputtering pressures on the thermoelectric properties of GeTe films. The working pressures were differentiated from 3 to 30 mTorr, and the as-deposited films were annealed at 623 K for 10 min in Ar atmosphere. The results show that the working pressure has a significant effect on the Ge content and crystalline size. The turning trend of the Seebeck coefficient with different sputtering pressures corresponds to the Ge content. The surface morphology of annealed film will change from cracks to voids with increasing sputtering pressure. This behavior can be explained by the growth mechanisms model. The voids and relatively low crystalline size of GeTe films affect to the reduction of the electrical conductivity. In addition, the void content decreased as film thickness was increased. Therefore, controlling the working pressures in the sputtering process and film thickness is important for the thermoelectric performance of GeTe thin film. In our work, we prove that the thermoelectric properties of GeTe films could be optimized effectively by simply tuning different sputtering conditions. (c) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Two-dimension (2D) nanomaterials with high specific area, low density and special electric behavior have attracted tremendous interest in the field of electromagnetic wave (EMW) absorption. Continuous and growing efforts have been committed to satisfy the demands of good impedance matching and strong attenuation capacity of 2D-based EMW absorption nanomaterials in past several years, and the ultimate aim of these materials is to develop potential candidates of high-performance absorption materials. In this review, we will summarize the latest progress (in the last four years) of 2D nanomaterials for EMW absorption, including graphene, MXenes, MoS2 nanosheets, layered double hydroxides (LDHs), graphite-like C3N4 (g-C3N4), and other representative transition metal dichalcogenides (TMDs). Moreover, the synthesis methods, structures, absorption mechanisms and performances of some excellent achievements will be presented. The aim of this review is to provide readers with a systematic overview of the relationship between 2D structures and absorption properties, and guide the future design of novel 2D electromagnetic wave absorption materials (EWAMs) by discussing the impedance matching and attenuation capacity of these recent advances. This review also intends to prompt fresh concepts for designing prominent high performances EWAMs. (C) 2021 Elsevier B.V. All rights reserved.
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