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1.
Chia-Jyi Liu Gao-Jhih Liu Chun-Wei Tsao Yo-Jhih Huang 《Journal of Electronic Materials》2009,38(7):1499-1503
We report on the successful hydrothermal synthesis of Bi0.5Sb1.5Te3, using water as the solvent. The products of the hydrothermally prepared Bi0.5 Sb1.5Te3 were hexagonal platelets with edges of 200–1500 nm and thicknesses of 30–50 nm. Both the Seebeck coefficient and electrical
conductivity of the hydrothermally prepared Bi0.5Sb1.5Te3 were larger than those of the solvothermally prepared counterpart. Hall measurements of Bi0.5Sb1.5Te3 at room temperature indicated that the charge carrier was p-type, with a carrier concentration of 9.47 × 1018 cm−3 and 1.42 × 1019 cm−3 for the hydrothermally prepared Bi0.5Sb1.5Te3 and solvothermally prepared sample, respectively. The thermoelectric power factor at 290 K was 10.4 μW/cm K2 and 2.9 μW/cm K2 for the hydrothermally prepared Bi0.5Sb1.5Te3 and solvothermally prepared sample, respectively. 相似文献
2.
Atmospheric water may condense on the surface of Bi2Te3-based compounds constituting the Peltier module, depending on the operating environment used. In the stage of disposal, Bi2Te3-based compounds may come into contact with water in waste disposal sites. There are very few publications about the influence of condensed water on Peltier modules. Bi2Te3-Sb2Te3 or Bi2Te3-Bi2Se3 pseudo binary system compounds are used as p-type material or n-type material, respectively. The lattice distortion will be induced in the crystal of Bi2Te3-based compounds by element substitution due to the reduction in their thermal conductivity. However, the influence of element substitution on the corrosion behavior of Bi2Te3-based compounds remains unclear. In this study, the influence of element substitution on the corrosion behavior of Bi2Te3-based compounds with practical compositions has been investigated. Bi0.5Sb1.5Te3 or Bi2Te2.85Se0.15 was prepared by the vertical Bridgman method. The electrochemical properties at room temperature were evaluated by cyclic voltammetry in a standard three-electrode cell. The working electrolyte was a naturally aerated 0.6 or 3.0 mass% NaCl solution. From the tendency for corrosion potential for all the samples, the corrosion sensitivity of ternary compounds was slightly higher than that of binary compounds. From the trend of current density, it was found that Bi0.5Sb1.5Te3 had a corrosion resistance intermediate between Bi2Te3 and Sb2Te3. On the other hand, corrosion resistance was affected despite a small amount of Se substitution, and the corrosion resistance of Bi2Te2.85Se0.15 was close to or lower than that of Bi2Se3. From the observation results of the corrosion products, the trends of morphology and composition of corrosion products for Bi0.5Sb1.5Te3 or Bi2Te2.85Se0.15 were consistent with those of Sb2Te3 or Bi2Se3, respectively. From the results of x-ray photoelectron spectroscopy for the electrolyte after testing, the possibility that a corrosion product diffuses to the environment including the salt was suggested in Bi0.5Sb1.5Te3. However, the amount of dissolved corrosion product was very low, and the chemical stability of the corrosion product was not changed or improved by element substitution. 相似文献
3.
HyunWoo You Sung-Hwan Bae Jongman Kim Jin-Sang Kim Chan Park 《Journal of Electronic Materials》2011,40(5):635-640
Nanocrystalline Bi2Te3 films were deposited on (100) GaAs substrates using a modified metalorganic chemical vapor deposition (MOCVD) system, and
the effect of growth parameters on the structural properties were investigated. The modified MOCVD system employed a mixing
room for the formation of nanoparticles of Bi2Te3 by gas-phase reaction and a graphite susceptor for growth of nanoparticles on the substrate. The grown films contained many
crystallites of nanosize, and large crystallites consisted of small particles a few tens of nanometer in size. This nanostructured
film approach can be an economical way of producing high-performance thermoelectric films with nanostructure compared with
other top-down methods. 相似文献
4.
Jan D. König M. Winkler S. Buller W. Bensch U. Schürmann L. Kienle H. Böttner 《Journal of Electronic Materials》2011,40(5):1266-1270
In this work, Bi2Te3-Sb2Te3 superlattices were prepared by the nanoalloying approach. Very thin layers of Bi, Sb, and Te were deposited on cold substrates,
rebuilding the crystal structure of V2VI3 compounds. Nanoalloyed super- lattices consisting of alternating Bi2Te3 and Sb2Te3 layers were grown with a thickness of 9 nm for the individual layers. The as-grown layers were annealed under different conditions
to optimize the thermoelectric parameters. The obtained layers were investigated in their as-grown and annealed states using
x-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive x-ray (EDX) spectroscopy, transmission electron
microscopy (TEM), and electrical measurements. A lower limit of the elemental layer thickness was found to have c-orientation. Pure nanoalloyed Sb2Te3 layers were p-type as expected; however, it was impossible to synthesize p-type Bi2Te3 layers. Hence the Bi2Te3-Sb2Te3 superlattices consisting of alternating n- and p-type layers showed poor thermoelectric properties. 相似文献
5.
Polycrystalline p-type Bi0.5Sb1.5Te3 and n-type Bi2Te2.7Se0.3 thermoelectric (TE) alloys containing a small amount (vol.% ≤5) of SiC nanoparticles were fabricated by mechanical alloying
and spark plasma sintering. It was revealed that the effects of SiC addition on TE properties can be different between p-type and n-type Bi2Te3-based alloys. SiC addition slightly increased the power factor of the p-type materials by decreasing both the electrical resistivity (ρ) and Seebeck coefficient (α), but decreased the power factor of n-type materials by increasing both ρ and α. Regardless of the conductivity type, the thermal conductivity was reduced by dispersing SiC nanoparticles in the Bi2Te3-based alloy matrix. As a result, a small amount (0.1 vol.%) of SiC addition increased the maximum dimensionless figure of
merit (ZT
max) of the p-type Bi0.5Sb1.5Te3 alloys from 0.88 for the SiC-free sample to 0.97 at 323 K, though no improvement in TE performance was obtained in the case
of n-type Bi2Te2.7Se0.3 alloys. Importantly, the SiC-dispersed alloys showed better mechanical properties, which can improve material machinability
and device reliability. 相似文献
6.
The results of studying the thermoelectric properties of p-type Bi0.5Sb1.5Te3 alloy samples prepared by melt spinning quenching are presented. The material after melt spinning is shaped as thin ribbons and has a quasi-amorphous structure. The thermoelectric properties (thermoelectric power and electrical resistance) and crystallization processes of as-prepared melt-spun ribbons are studied at 300–800 K for the first time. The stability range of the initial state, the crystallization-onset temperature, and the effect of thermal annealing on the thermoelectric-power factor of the alloy are determined. 相似文献
7.
The results of studying the galvanomagnetic and thermoelectric properties of thin block Bi92Sb8 and Bi85Sb15 films on mica and polyimide substrates are presented. The method used for measuring the thermoelectric power allowed us to study the temperature dependence the thermoelectric power, without introducing additional deformations into the substrate–film system. A significant difference in the temperature dependences of the galvanomagnetic and thermoelectric properties of films on mica and polyimide is found. The free charge-carrier concentrations and mobilities in the films on mica and polyimide and levels of the chemical potential for electrons and holes are calculated within the two-band approximation. The difference in the charge-carrier parameters for films on mica and polyimide is associated with strains in the film–substrate system. 相似文献
8.
Reflectance spectra of single crystals of Bi2Te3-Sb2Te3 solid solutions containing 0, 10, 25, 40, 50, 60, 65, 70, 80, 90, 99.5, and 100 mol % of Sb2Te3 have been studied in the range of 400–4000 cm−1 at the temperature T = 291 K and with orientation of the vector of the electric-field strength E perpendicular to the trigonal axis of the crystal C
3 (E ⊥ C
3). The shape of the spectra is characteristic of plasma reflection; the spectra include the features in the range 1250–3000
cm−1 corresponding to the optical band gap E
g opt. The features become more pronounced as the content of Bi2Te3 is increased to 80 mol % in the composition of the Bi2Te3-Sb2Te3 solid solution. A further increase in the content of Sb2Te3 is accompanied by discontinuities in the functional dependences of the parameters characterizing the plasma oscillations
of free charge carriers on the solid-solution composition and also by a sharp increase in E
g opt. 相似文献
9.
H. Kitagawa A. Kurata H. Araki S. Morito E. Tanabe 《Journal of Electronic Materials》2010,39(9):1692-1695
The effects of deformation temperature on texture and thermoelectric properties of p-type Bi0.5Sb1.5Te3 sintered materials were investigated. The sintered materials were prepared by mechanical alloying and hot-press sintering.
The hot-press deformation was performed at 723 K and 823 K by applying mechanical pressure in a graphite die. Then, the materials
were extruded in the direction opposite to the direction of applied pressure. X-ray diffraction and electron backscattered
diffraction patterns showed that the hexagonal c-plane tended to align along the extruded direction when the samples were deformed at high temperatures. The thermoelectric
power factor was increased by high-temperature hot-press deformation because of the low electrical resistivity that originated
from the c-plane orientation. 相似文献
10.
Jae-Hong Lim Mi Yeong Park Dong Chan Lim Bongyoung Yoo Jung-Ho Lee Nosang V. Myung Kyu Hwan Lee 《Journal of Electronic Materials》2011,40(5):1321-1325
Thermoelectric Sb
x
Te
y
films were potentiostatically electrodeposited in aqueous nitric acid electrolyte solutions containing different concentrations
of TeO2. Stoichiometric Sb
x
Te
y
films were obtained by applying a voltage of −0.15 V versus saturated calomel electrode (SCE) using a solution consisting
of 2.4 mM TeO2, 0.8 mM Sb2O3, 33 mM tartaric acid, and 1 M HNO3. The nearly stoichiometric Sb2Te3 films had a rhombohedral structure, R[`3]m R\bar{3}m , with a preferred orientation along the (015) direction. The films had hole concentration of 5.8 × 1018/cm3 and exhibited mobility of 54.8 cm2/Vs. A more negative potential resulted in higher Sb content in the deposited Sb
x
Te
y
films. Furthermore, it was observed that the hole concentration and mobility decreased with increasingly negative deposition
potential, and eventually showed insulating properties, possibly due to increased defect formation. The absolute value of
the Seebeck coefficient of the as-deposited Sb2Te3 thin film at room temperature was 118 μV/K. 相似文献
11.
Sang-Ouk Ryu 《Journal of Electronic Materials》2008,37(4):535-539
A phase-change memory device that utilizes an antimony (Sb)-excess Ge15Sb47Te38 chalcogenide thin film was fabricated and its electrical properties were measured and compared with a similar device that
uses Ge22Sb22Te56. The resulting electrical characteristics exhibited I
reset values of 14 mA for Ge22Sb22Te56 and 10.6 mA for Ge15Sb47Te38. Also, the set operation time (t
set) for the device using Ge15Sb47Te38 films was 140 ns, which was more than twice as fast as the Ge22Sb22Te56 device. The relationship between the microstructure and the improved electrical performance of the device was examined by
means of transmission electron microscopy (TEM). 相似文献
12.
Huqin Zhang Jian He Bo Zhang Zhe Su Terry M. Tritt Navid Soheilnia Holger Kleinke 《Journal of Electronic Materials》2007,36(7):727-731
Mo3Sb7, crystallizing in the Ir3Ge7 type structure, has poor thermoelectric (TE) properties due to its metallic behavior. However, by a partial Sb-Te exchange,
it becomes semiconducting without noticeable structure changes and so achieves a significant enhancement in the thermopower
with the composition of Mo3Sb5Te2. Meanwhile, large cubic voids in the Mo3Sb5Te2 crystal structure provide the possibility of filling the voids with small cations to decrease the thermal conductivity by
the so-called rattling effect. As part of the effort to verify this idea, we report herein the growth as well as measurements
of the thermal and electrical transport properties of Mo3Sb5.4Te1.6 and Ni0.06Mo3Sb5.4Te1.6. 相似文献
13.
Cu0.003Bi0.4Sb1.6Te3 alloys were prepared by using encapsulated melting and hot extrusion (HE). The hot-extruded specimens had the relative average density of 98%. The (00l) planes were preferentially oriented parallel to the extrusion direction, but the specimens showed low crystallographic anisotropy with low orientation factors. The specimens were hot-extruded at 698 K, and they showed excellent mechanical properties with a Vickers hardness of 76 Hv and a bending strength of 59 MPa. However, as the HE temperature increased, the mechanical properties degraded due to grain growth. The hot-extruded specimens showed positive Seebeck coefficients, indicating that the specimens have p-type conduction. These specimens exhibited negative temperature dependences of electrical conductivity, and thus behaved as degenerate semiconductors. The Seebeck coefficient reached the maximum value at 373 K and then decreased with increasing temperature due to intrinsic conduction. Cu-doped specimens exhibited high power factors due to relatively higher electrical conductivities and Seebeck coefficients than those of undoped specimens. A thermal conductivity of 1.00 Wm?1 K?1 was obtained at 373 K for Cu0.003Bi0.4Sb1.6Te3 hot-extruded at 723 K. A maximum dimensionless figure of merit, ZT max = 1.05, and an average dimensionless figure of merit, ZT ave = 0.98, were achieved at 373 K. 相似文献
14.
Tae-Sung Oh 《Journal of Electronic Materials》2009,38(7):1041-1047
The p-type (Bi,Sb)2Te3/(Pb,Sn)Te functional gradient materials (FGMs) were fabricated by hot-pressing mechanically alloyed (Bi0.2Sb0.8)2Te3 and 0.5 at.% Na2Te-doped (Pb0.7Sn0.3)Te powders together at 500°C for 1 h in vacuum. Segment ratios of (Bi,Sb)2Te3 to (Pb,Sn)Te were varied as 3:1, 1.3:1, and 1:1.6. A reaction layer of about 350-μm thickness was formed at the (Bi,Sb)2Te3/(Pb,Sn)Te FGM interface. Under temperature differences larger than 340°C applied across a specimen, superior figures of merit
were predicted for the (Bi,Sb)2Te3/(Pb,Sn)Te FGMs to those of (Bi0.2Sb0.8)2Te3 and (Pb0.7Sn0.3)Te. With a temperature difference of 320°C applied across a specimen, the (Bi,Sb)2Te3/(Pb,Sn)Te FGMs with segment ratios of 3:1 and 1.3:1 exhibited the maximum output powers of 72.1 mW and 72.6 mW, respectively,
larger than the 63.9 mW of (Bi0.2Sb0.8)2Te3 and the 26 mW of 0.5 at.% Na2Te-doped (Pb0.7Sn0.3)Te. 相似文献
15.
In this work, nano-structured Bi2Te3 and PbTe thermoelectric materials were synthesized separately via solvothermal, hydrothermal and low-temperature aqueous
chemical routes. X-ray diffraction (XRD), field-emission scanning-electron microscopy (FESEM), transmission electron microscopy
(TEM), and energy dispersive spectroscopy (EDS) were used to analyze the powder products. Results showed that the as-prepared
Bi2Te3 samples were all single-phased and consisted of irregular spherical granules with diameters of ∼30 nm whereas the PbTe samples
were mainly composed of well-crystallized cubic crystals with average size of approximately 100 nm. Some nanotubes and nanorods
were found in Bi2Te3 and PbTe samples, respectively; these were identified as Bi2Te3 nanotubes and PbTe nanorods by EDS analysis. Possible reaction mechanisms for these syntheses are discussed in detail herein. 相似文献
16.
N. A. Abdullaev N. M. Abdullaev H. V. Aliguliyeva T. G. Kerimova G. S. Mehdiyev S. A. Nemov 《Semiconductors》2011,45(1):37-42
The temperature dependences (T = 5−300 K) of the resistivity in the plane of layers and in the direction perpendicular to the layers, as well as the Hall
effect and the magnetoresistance (H < 80 kOe, T = 0.5−4.2 K) in Bi2Te3 single crystals doped with chlorine and terbium, are investigated. It is shown that the doping of Bi2Te3 with terbium atoms results in p-type conductivity and in increasing hole concentration. The doping of Bi2Te3 with chlorine atoms modifies also the character of its conductivity instead of changing only the type from p to n. In the temperature dependence of the resistivity in the direction perpendicular to layers, a portion arises with the activation
conductivity caused by the hopping between localized states. The charge-transport mechanism in Bi2Te3 single crystals doped with chlorine is proposed. 相似文献
17.
The magnetic susceptibility of Czochralski-grown single crystals of Bi2Te3-Sb2Te3 alloys containing 0, 10, 25, 40, 50, 60, 65, 70, 80, 90, 99.5, or 100 mol % Sb2Te3 has been investigated. The magnetic susceptibility of these crystals was determined at the temperature T = 291 K and the magnetic field H oriented parallel (χ‖) and perpendicularly (χ⊥) to the trigonal crystallographic axis C 3. A complicated concentration dependence of the anisotropy of magnetic susceptibility χ‖/χ⊥ has been revealed. The crystals with the free carrier concentration p ≈ 5 × 1019 cm?3 do not exhibit anisotropy of magnetic susceptibility. The transition to the isotropic magnetic state occurs for the compositions characterized by a significantly increased (from 200 to 300 meV) optical bandgap. 相似文献
18.
Vijayaharan A. Venugopal Giampiero Ottaviani Camillo Bresolin Davide Erbetta Alberto Modelli Enrico Varesi 《Journal of Electronic Materials》2009,38(10):2063-2068
The thermal stability of a Ge2Sb2Te5 chalcogenide layer in contact with titanium and titanium nitride metallic thin films has been investigated mainly using x-ray
diffraction and elastic nuclear backscattering techniques. Without breaking vacuum, Ti and TiN have been deposited on Ge2Sb2Te5 material using magnetron sputtering. Thermal treatments have been performed in a 10−7 mbar vacuum furnace. On annealing up to 450°C, the TiN metallic film does not interact with the chalcogenide film, but at
the same time adhesion problems and instabilities in contact resistance arise. To improve the adhesion and eventually stabilize
the contact resistance, an interfacial Ti layer has been considered. At 300°C, a TiTe2 compound is formed by interacting with Te segregated from the Ge2Sb2Te5 layer. At higher temperatures, the Ti layer decomposes the chalcogenide film, forming several compounds tentatively identified
as GeTe, Ge3Ti5, Ge5Ti6, TiTe2,, and Sb2Te3. It has been found that the properties of the Ge2Sb2Te5 film can be retained by controlling the decomposition rate of the chalcogenide layer, which is achieved by providing a limited
supply of Ti and/or by depositing a Te-rich Ge2Sb2Te5 film. 相似文献
19.
Ruixue Chen Qingsen Meng Wenhao Fan Liqi Wang Zhong Wang 《Journal of Electronic Materials》2011,40(5):765-768
Field-activated pressure-assisted sintering (FAPAS) was applied to sinter Bi1.2Sb4.8Te9 thermoelectric materials under different conditions, including no-current sintering (NCS), low-density current sintering
(LCS), and high-density current sintering (HCS). The effect of the current density on the final thermoelectric performance
of the products was investigated. Applying a higher-density electric current and shorter dwell time can improve the thermoelectric
performance of the sample by increasing its electric conductivity and decreasing its thermal conductivity. The maximum figure
of merit ZT values of the NCS, LCS, and HCS samples were 0.46, 0.48, and 0.57, respectively. Therefore, applying a high-density electric
current in the sintering process may be an effective way to obtain Bi1.2Sb4.8Te9 thermoelectric material with high ZT value. 相似文献
20.
Asaithambi Suresh Krishanu Chatterjee Vijay Kr. Sharma Saibal Ganguly Kajari Kargupta Dipali Banerjee 《Journal of Electronic Materials》2009,38(3):449-452
Bi2Te3 thin films were electrodeposited at various pH values of a bismuth nitrate and tellurium oxide plating solution. Enhancement
in pH results in a decrease in grain size. Transmission electron microscopy reveals the transformation of the film morphology
from dispersed nanoparticles to connected chain-like nanostructures of Bi2Te3 as pH is increased. Electrical characterization for samples deposited in the temperature range of 300 K to 425 K shows a
fourfold increase in Seebeck coefficient, S, between its maximum and minimum value as the solution pH changes from 1 to 3.5. Such enhancement of S is attributed to the increased connectivity of the nanostructures at higher pH. 相似文献