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1.
The effect the conditions of preparing thermoelectric solid solutions of Bi0.5Sb1.5Te3 + 0.06 wt % Pb by hardening from the liquid state with subsequent hot pressing have on their thermoelectric properties is studied. It is found that the optimum thermoelectric quality factors are achieved at a 2200–2800 rpm rate of copper disc rotation.  相似文献   

2.
Spectra of optical absorption in Bi0.5Sb1.5Te3 films grown on mica and KBr substrates have been investigated for T = 145 and 300 K. The data obtained have been analyzed together with the data of investigations on the fundamental absorption edge for Bi2Te3 available in the scientific literature. It has been revealed that the interband absorption spectra for both Bi0.5Sb1.5Te3 and Bi2Te3 represent a superposition of two components corresponding to direct and indirect allowed optical transitions. In this case, the least energy gap separating the valence band and the conduction band is direct for Bi2−xSbxTe3 (x ≤ 1.5, T = 300 K). For Bi0.5Sb1.5Te3 the temperature variation rates have been estimated for the thresholds of direct and indirect interband transitions. It has been shown that this solid solution is direct gap solution at T ≥ 145 K. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 50–52, July, 2008.  相似文献   

3.
This work considers the effect of vacuum annealing on the thermoelectric properties of Sb0.9Bi1.1Te2.9Se0.1 thin film and Sb0.9Bi1.1Te2.9Se0.1–C composites with various carbon contents produced by ion-beam deposition in an argon atmosphere. The electrical resistivity and the thermopower of Sb0.9Bi1.1Te2.9Se0.1–C nanocomposites are found to be dependent on not only the carbon concentration but also the type and the concentration of intrinsic point defects of the Sb0.9Bi1.1Te2.9Se0.1 solid solution, which determine the type of conductivity of Sb0.9Bi1.1Te2.9Se0.1 granules. The power factors are estimated for films of Sb0.9Bi1.1Te2.9Se0.1 solid solution and films of Sb0.9Bi1.1Te2.9Se0.1–C composites and found to have values comparable with the values for nanostructured materials on the basis of (Bi,Sb)2(Te,Se)3 solid solutions.  相似文献   

4.
The effect thermal treatment in a vacuum has on the thermoelectric properties of Sb0.9Bi1.1Te2.9Se0.1 solid solution thin films obtained via ion-beam sputtering in an argon atmosphere is considered. It is established that the specific resistance and thermopower are determined by the type and concentration of intrinsic point defects of the Sb0.9Bi1.1Te2.9Se0.1 solid solution. The power factor values are found to be comparable to those of nanostructured materials based on (Bi,Sb)2(Te,Se)3 solid solutions.  相似文献   

5.
Thin films of Sb2Te3 and (Sb2Te3)70(Bi2Te3)30 alloy and have been deposited on precleaned glass substrate by thermal evaporation technique in a vacuum of 2?×?10?6 Torr. The structural study was carried out by X-ray diffractometer, which shows that the films are polycrystalline in nature. The grain size, microstrain and dislocation density were determined. The Seebeck coefficient was determined as the ratio of the potential difference across the films to the temperature difference. The power factor for the (Sb2Te3)70 (Bi2Te3)30 and (Sb2Te3) is found to be 19.602 and 1.066 of the film of thickness 1,500 Å, respectively. The Van der-Pauw technique was used to measure the Hall coefficient at room temperature. The carrier concentration was calculated and the results were discussed.  相似文献   

6.
The effect of Ga doping on the temperature dependences (5 K ≤ T ≤ 300 K) of the Seebeck coefficient α, electrical conductivity σ, thermal conductivity coefficient κ, and thermoelectric figure of merit Z of p-(Bi0.5Sb0.5)2Te3 single crystals has been investigated. It has been shown that, upon Ga doping, the hole concentration decreases, the Seebeck coefficient increases, the electrical conductivity decreases, and the thermoelectric figure of merit increases. The observed variations in the Seebeck coefficient cannot be completely explained by the decrease in the hole concentration and indicate a noticeable variation in the density of states due to the Ga doping.  相似文献   

7.
The results of the theoretical investigation of the surface electronic structure of A2VB3VI compounds containing topologically protected surface states are reported. The ideal Bi2Te3, Bi2Se3, and Sb2Te3 surfaces and surfaces with an absent external layer of chalcogen atoms, which were observed experimentally as monolayer terraces, have been considered. It has been shown that the discrepancy between the calculated Fermi level and the value measured in the photoemission experiments can be attributed to the presence of the “dangling bond” states on the surface of the terraces formed by semimetal atoms. The fraction of such terraces on the surface has been estimated.  相似文献   

8.
The specific features of the electronic and spin structures of a triple topological insulator Bi2Te2.4Se0.6, which is characterized by high-efficiency thermoelectric properties, have been studied with the use of angular- and spin-resolved photoelectron spectroscopy and compared with theoretical calculations in the framework of the density functional theory. It has been shown that the Fermi level for Bi2Te2.4Se0.6 falls outside the band gap and traverses the topological surface state (the Dirac cone). Theoretical calculations of the electronic structure of the surface have demonstrated that the character of distribution of Se atoms on the Te–Se sublattice practically does not influence the dispersion of the surface topological electronic state. The spin structure of this state is characterized by helical spin polarization. Analysis of the Bi2Te2.4Se0.6 surface by scanning tunnel microscopy has revealed atomic smoothness of the surface of a sample cleaved in an ultrahigh vacuum, with a lattice constant of ~4.23 Å. Stability of the Dirac cone of the Bi2Te2.4Se0.6 compound to deposition of a Pt monolayer on the surface is shown.  相似文献   

9.
The electrochemical behaviors of BiIII, TeIV and SbIII single ions and their mixtures were investigated in nitric acid and hydrochloric acid system separately. Based on which, BixSb2−xTey thermoelectric films were prepared by potentiostatic electrodeposition from the solutions with different concentrations of BiIII, TeIV and SbIII in the two acid systems. The morphologies, compositions, structures, Seebeck coefficients and resistivities of the deposited thin films were characterized and compared by ESEM (or FESEM), EDS, XRD, Seebeck coefficient measurement system and four-probe resistivity measuring device respectively. The results show that although BixSb2−xTey thermoelectric thin film which structure is consistent with the standard pattern of Bi0.5Sb1.5Te3 can be gained in both of the two acid solutions by adjusting the deposition potential, their morphologies and thermoelectric properties have big differences in different acid solutions.  相似文献   

10.
Epitaxial c-oriented Bi2Te3 films 1.2 μm in thickness are grown by the hot wall method for a low supersaturation of the vapor phase over the surface of mica substrates. The hexagonal unit cell parameters a = 4.386 Å and c = 30.452 Å of the grown films almost coincide with the corresponding parameters of stoichiometric bulk Bi2Te3 crystals. At T = 100 K, the Hall concentration of electrons in the films is on the order of 8 × 1018 cm?3, while the highest values of the thermoelectric coefficient (α ≈ 280 μV K?1) are observed at temperatures on the order of 260 K. Under impurity conduction conditions, conductivity σ of the films increases upon cooling in inverse proportion to the squared temperature. In the temperature range 100–200 K, thermoelectric power parameter α2σ of Bi2Te3 films has values of 80–90 μW cm?1 K?2.  相似文献   

11.
The Fermi surface anisotropy of (Bi1?x Sbx)2Te3 single crystals (0.25 ≤ x ≤ 1) was studied by analyzing the angular dependence of the frequency of Shubnikov-de Haas oscillations and the effect of tin and silver doping on the thermoelectric power in these crystals in the temperature range 77 ≤ T ≤ 300 K. It was shown that silver doping of (Bi1?x Sbx)2Te3 mixed crystals produces acceptors, while silver in Bi2Te3 acts as a donor. Tin also exhibits acceptor properties. Both tin and silver doping of p-(Bi1?x Sbx)2Te3 mixed crystals decrease the thermoelectric power due to an increase in the hole concentration.  相似文献   

12.
Theoretical studies of the bulk and surface electronic structures of PbBi4Te7 are presented. The PbBi4Te7 compound has a layered structure of five-layer (Bi2Te3) and seven-layer (PbBi2Te4) blocks alternating along the hexagonal axis. Analysis of the spin-orbit-induced inversion of the band gap edges indicates that this compound is a three-dimensional topological insulator. The topological properties of this compound are mainly determined by the PbBi2Te4 blocks. The Dirac cone is formed on the PbBi4Te7(0001) surface near the $ \bar \Gamma $ \bar \Gamma point for any block (either Bi2Te3 or PbBi2Te4) forming the surface. It is shown that the Dirac state can be localized not only on the surface but also deeply beneath it.  相似文献   

13.
The effect of an ultrathin Pb film deposited on the surface of Bi2Se3 and Sb2Te3 compounds on the electronic state structure of topological insulators is studied experimentally by the angle-resolved photoemission spectroscopy (ARPES) technique. The following features are revealed: formation of two-dimensional quantum-well states in the near-surface region, an increase in the binding energy of the Dirac cone and the core levels, and a simultaneous electronic states intensity redistribution in the system in photoemission spectra. The results obtained show that topological states may coexist at the interface between studied materials and a superconductor, which seems to be promising for application in quantum computers.  相似文献   

14.
We present a laser-based transfer method for the novel application of fabricating elements for planar thermoelectric devices. Thin films of thermoelectric chalcogenides (Bi2Te3, Bi2Se3 and Bi0.5Sb1.5Te3) were printed via laser-induced forward transfer (LIFT) onto polymer-coated substrates over large areas of up to ~15 mm2 in size. A morphological study showed that it was possible to partially preserve the polycrystalline structure of the transferred films. The films’ Seebeck coefficients after LIFT transfer were measured and resulted in ?49±1 μV/K, ?93±8 μV/K and 142±3 μV/K for Bi2Te3, Bi2Se3 and Bi0.5Sb1.5Te3, respectively, which were found to be ~23±6 % lower compared to their initial values. This demonstration shows that LIFT is suitable to transfer sensitive, functional semiconductor materials over areas up to ~15 mm2 with minimal damage onto a non-standard polymer-coated substrate.  相似文献   

15.
The effect of suppression of intrinsic conduction in the narrow-band-gap p-Bi0.5Sb1.5Te3 semiconductor subjected to plastic deformation is revealed. The effect consists in slowing down the decrease in the thermopower coefficient at high temperatures due to intrinsic conduction. The observed effect can be caused by an enhancement of the misorientation of crystal grains or by the formation of linear structural defects (dislocations, microcracks), which are responsible for the decrease in the mobility of predominantly minority charge carriers.  相似文献   

16.
范平  蔡兆坤  郑壮豪  张东平  蔡兴民  陈天宝 《物理学报》2011,60(9):98402-098402
本文采用离子束溅射Bi/Te和Sb/Te二元复合靶,直接制备n型Bi2Te3热电薄膜和p型Sb2Te3热电薄膜.在退火时间同为1 h的条件下,对所制备的Bi2Te3薄膜和Sb2Te3薄膜进行不同温度的退火处理,并对其热电性能进行表征.结果表明,在退火温度为150 ℃时,制备的n型Bi2Te3关键词: 薄膜温差电池 2Te3薄膜')" href="#">Sb2Te3薄膜 2Te3薄膜')" href="#">Bi2Te3薄膜 离子束溅射  相似文献   

17.
P-type Bi2Te3-based thermoelectric semiconductors were prepared, having a grain-refined microstructure and a preferred orientation of anisotropic crystallographic structure. Disks with a nominal composition of Bi0.5Sb1.5Te3.0 were cut from an ingot grown by the vertical Bridgman method (VBM) and deformed at 473 K under a pressure of 6.0 GPa by high-pressure torsion (HPT). The crystal orientation was characterized by X-ray diffraction. The microstructures were characterized using optical microscopy and scanning electron microscopy (SEM). It was found that the HPT disks had a fine and preferentially oriented grain compared to that of the VBM disks. Further, the power factor of the HPT disks was about twice as large as that of the VBM disks. These results indicate that HPT is effective in improving the thermoelectric properties of Bi2Te3-based thermoelectric semiconductors.  相似文献   

18.
Based on the results of electron density functional calculations of the electronic band structure of semiconductors Sb2Te3, Ge, Te, and semimetal Sb, the parameters of critical points in the electron density distribution (maxima, minima, and saddle points) in the lattices of the above materials are found. The data obtained are used to analyze the chemical bond nature in Sb2Te3.  相似文献   

19.
The temperature dependence of the Raman spectra of Bi2Te3 and Bi0.5Sb1.5Te3 thermoelectric films was investigated. The temperature coefficients of the Eg(2) peak positions were determined as –0.0137 cm–1/°C and –0.0156 cm–1/°C, respectively. The thermal expansion of the crystal caused a linear shift of the Raman peak induced by the temperature change. Based on the linear relation, a reliable and noninvasive micro‐Raman scattering method was shown to measure the thermal conductivity of the thermoelectric films. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

20.
We have investigated the structural and thermoelectric properties of (Sb1-xBix)2Te3 thin films on CdTe(111)B. Analysis of X-ray diffraction patterns (–2 scans and rocking curves) of the films shows that they are of high quality and that they are well aligned with their (00.1) axis normal to the substrates. Measurements of the temperature-dependent thermoelectric power, resistivity, and Hall coefficient of the films were performed with respect to the binary composition, x. For the samples in the range 0.2<x<0.3, the room-temperature thermopower values were in the range 159–184 V/K, the room-temperature carrier concentrations were 3.93–5.13×1019 cm-3, and the room-temperature mobilities were 24.6–64.0 cm2V-1s-1. PACS 72.20.Pa; 72.80.Jc; 73.6l.Le  相似文献   

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