In this study, we report the fabrication of n-type flexible thermoelectric fabrics using layered Bi2Se3 nanoplate/polyvinylidene fluoride (PVDF) composites as the thermoelectric material. These ...composites exhibit room temperature Seebeck coefficient and electrical conductivity values of −80 μV K–1 and 5100 S m–1, respectively, resulting in a power factor approaching 30 μW m–1K–2. The temperature-dependent thermoelectric properties reveal that the composites exhibit metallic-like electrical conductivity, whereas the thermoelectric power is characterized by a heterogeneous model. These composites have the potential to be used in atypical applications for thermoelectrics, where lightweight and flexible materials would be beneficial. Indeed, bending tests revealed excellent durability of the thermoelectric fabrics. We anticipate that this work may guide the way for fabricating high performance thermoelectric fabrics based on layered V–VI nanoplates.
We investigated spin-to-charge conversion in sputtered Bi43Se57/Co20Fe60B20 heterostructures with in-plane magnetization at room temperature. High spin-to-charge conversion voltage signals have been ...observed at room temperature. The transmission electron microscope images show that the sputtered bismuth selenide thin films are nanogranular in structure. The spin-pumping voltage decreases with an increase in the size of the grains. The inverse Edelstein effect length (λIEE) is estimated to be as large as 0.32 nm. The large λIEE is due to the spin-momentum locking and is further enhanced by quantum confinement in the nanosized grains of the sputtered bismuth selenide films. We also investigated the effect on spin-pumping voltage due to the insertion of layers of MgO and Ag. The MgO insertion layer has almost completely suppressed the spin-pumping voltage, whereas the Ag insertion layer has enhanced the λIEE by 43%.
In this paper, we synthesized Bi2Se3-NFs@rGO composite and analyzed electro chemical properties. Bi2Se3-NFs@rGO composite improved specific capacity, cycle stability and ion conductivity by rGO ...composite.
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•The synthesis of Bi2Se3 nanoflakes(NFs) by organic molecules as selenium precursor.•Synthesized homogenously nanoflakes by oleylamine as surfactant.•Bi2Se3-NFs@rGO composite exhibits high specific capacity compared to previous articles.•Analyzed the mechanism of Bi2Se3-NFs@rGO composite via Ex-situ TEM and Ex-situ XRD.
Metal selenides have gained attention as alternative anode materials for lithium-ion batteries, with increasing demand for electro-vehicles and appliances. Bismuth selenide has significant potential as anode materials in lithium-ion batteries. Nevertheless, metal selenides have essential drawbacks, such as volume expansion and poor cycle performance. In this paper, bismuth selenide synthesized homogeneous morphology-like nanoflakes (NFs) using the wet chemical method. We combined these nanoflakes with reduced graphene oxide to improve their structural stability. The Bi2Se3-NFs@rGO composite showed enhanced specific capacity from 750 mAhg−1 to 1100 mAhg−1 at 100 mAg−1. Furthermore, at a current density of 500 mAg−1, it reached a specific capacity (819 mAhg−1) after 300 cycles and demonstrated a coulombic efficiency of 96 %.
A method is presented that enables the template assisted electrochemical deposition of tens of micrometer thick, compact and stoichiometric Bi2Se3 micropillars. This is achieved by modifying the ...acidic electrolyte that contains 1 M HNO3 with potassium chloride salt and introducing resting pulses during the plating process. We demonstrate the successful deposition into photoresist templates with mold diameters down to 30 µm and thicknesses up to 45 µm. Cross-sectional EDX line measurements confirm an optimal stoichiometry of Bi:Se 40:60 along the growth direction, independent of the micropillar diameter. XRD and Raman measurements after electrochemical deposition point to a primarily orthorhombic structure. To illustrate the potential of this electrochemical method for thermoelectric applications, Seebeck coefficient and electrical conductivity of 45 µm thick orthorhombic Bi2Se3 pillars with 30 and 50 µm diameter are measured for five different electrodeposition runs. An average electrical conductivity of 8.6 S/m (SD = 4.5 S/m) and a high average negative Seebeck coefficient of -162 µV/K (SD = 32 µV/K) was determined. The process presented here is highly promising for the reliable synthesis of Bi2Se3 micropillars, which can be integrated in thermoelectric micro generators or sensors.
Two new barium iron pnictide–selenides, Ba2FeSbSe5 and Ba2FeBiSe5, were synthesized by a high-temperature solid-state route and their crystal structures were determined using single crystal X-ray ...diffraction. Both compounds are isomorphic to the high pressure phase Ba3FeS5 and crystallize in the orthorhombic space group Pnma (No. 62) with cell parameters of a=12.603(2)/12.619(2)Å, b=9.106(1)/9.183(1)Å, c=9.145(1)/9.123(1)Å and Z=4 for Ba2FeSbSe5 and Ba2FeBiSe5, respectively. According to differential scanning calorimetry, Ba2FePnSe5 compounds exhibit high thermal stability and melt congruently at 1055(5)K (Pn=Sb) and 1105(5)K (Pn=Bi). Magnetic characterizations reveal strong antiferromagnetic nearest-neighbor interactions in both compounds resulting in an antiferromagnetic ordering at 58(1)K for Ba2FeSbSe5 and 79(2)K for Ba2FeBiSe5. The magnetic interactions between Fe3+ centers, which are at least 6Å apart from each other, are mediated by superexchange interactions.
In Ba2FeSbSe5 and Ba2FeBiSe5 the magnetic interactions between Fe3+ centers, which are at least 6 Å apart from each other, are mediated by superexchange interactions.
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•New compounds Ba2FeSbSe5 and Ba2FeBiSe5 have been synthesized.•The crystal structure was determined by single crystal X-ray diffraction.•Both compounds melt congruently at temperatures above 1000K.•Ba2FeSbSe5 and Ba2FeBiSe5 exhibit AFM ordering at 58K (Sb) and 70K (Bi).•Magnetic exchange between Fe3+ is mediated by either Se–Sb(Bi)–Se or Se–Ba–Se bridges.
We report on the electronic states and the transport properties of three-dimensional topological insulator (Bi1−xSbx)2Se3 ternary alloy thin films grown on an isostructural Bi2Se3 buffer layer on InP ...substrates. By angle-resolved photoemission spectroscopy, we clearly detected Dirac surface states with a large bulk band gap of 0.2-0.3 eV in the (Bi1−xSbx)2Se3 film with x = 0.70. In addition, we observed by Hall effect measurements that the dominant charge carrier converts from electron (n-type) to hole (p-type) at around x = 0.7, indicating that the Fermi level can be controlled across the Dirac point. Indeed, the carrier transport was shown to be governed by Dirac surface state in 0.63 x 0.75. These features suggest that Fermi-level tunable (Bi1−xSbx)2Se3-based heterostructures provide a platform for extracting exotic topological phenomena.
The topologically protected surface states of three-dimensional (3D) topological insulators have the potential to be transformative for high-performance logic and memory devices by exploiting their ...specific properties such as spin-polarized current transport and defect tolerance due to suppressed backscattering. However, topological insulator based devices have been underwhelming to date primarily due to the presence of parasitic issues. An important example is the challenge of suppressing bulk conduction in Bi2Se3 and achieving Fermi levels (E F) that reside in between the bulk valence and conduction bands so that the topologically protected surface states dominate the transport. The overwhelming majority of the Bi2Se3 studies in the literature report strongly n-type materials with E F in the bulk conduction band due to the presence of a high concentration of selenium vacancies. In contrast, here we report the growth of near-intrinsic Bi2Se3 with a minimal Se vacancy concentration providing a Fermi level near midgap with no extrinsic counter-doping required. We also demonstrate the crucial ability to tune E F from below midgap into the upper half of the gap near the conduction band edge by controlling the Se vacancy concentration using post-growth anneals. Additionally, we demonstrate the ability to maintain this Fermi level control following the careful, low-temperature removal of a protective Se cap, which allows samples to be transported in air for device fabrication. Thus, we provide detailed guidance for E F control that will finally enable researchers to fabricate high-performance devices that take advantage of transport through the topologically protected surface states of Bi2Se3.
Bi2Se3 attracts intensive attention as a typical thermoelectric material and a promising topological insulator material. However, previously reported Bi2Se3 nanostructures are limited to nanoribbons ...and smooth nanoplates. Herein, we report the synthesis of spiral Bi2Se3 nanoplates and their screw‐dislocation‐driven (SDD) bidirectional growth process. Typical products showed a bipyramid‐like shape with two sets of centrosymmetric helical fringes on the top and bottom faces. Other evidence for the unique structure and growth mode include herringbone contours, spiral arms, and hollow cores. Through the manipulation of kinetic factors, including the precursor concentration, the pH value, and the amount of reductant, we were able to tune the supersaturation in the regime of SDD to layer‐by‐layer growth. Nanoplates with preliminary dislocations were discovered in samples with an appropriate supersaturation value and employed for investigation of the SDD growth process.
Interesting faces with chiseled features: No longer limited to nanoribbons and smooth nanoplates, Bi2Se3 nanostructures in the form of spiral‐type nanoplates with a bipyramid‐like shape characterized by two sets of centrosymmetric helical fringes on the top and bottom faces were formed by a bidirectional growth process. Other evidence for the unique structure and growth mode include herringbone contours, spiral arms, and hollow cores (see picture).
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