共查询到20条相似文献,搜索用时 15 毫秒
1.
Bismuth telluride-based compounds have been extensively utilized for commercial application. However, thermoelectric materials must suffer numerous mechanical vibrations and thermal stresses while in service, making it equally important to discuss the mechanical properties, especially at high temperature. In this study, the compressive and bending strengths of Bi 0.5Sb 1.5Te 3 commercial zone melting (ZM) ingots were investigated at 25, 100, and 200 °C, respectively. Due to the obvious anisotropy of materials prepared by ZM method, the effect of anisotropy on the strengths was also explored. Two-parameter Weibull distribution was employed to fit a series of values acquired by a universal testing machine. And digital speckle photography was applied to record the strain field evolution, providing visual observation of surface strain. The compressive and bending strengths along ZM direction were approximately three times as large as those perpendicular to the ZM direction independent of the temperature, indicating a weak van der Waals bond along the c axis. 相似文献
3.
The present study focused on synthesis of Bi 0.5Sb 1.5Te 3 thermoelectric powder using an oxide-reduction process. The phase structure and particle size of the synthesized powders were analyzed using x-ray diffractometry and scanning electron microscopy. The synthesized powder was sintered using the spark plasma sintering method. The thermoelectric properties of the sintered body were evaluated by measuring the Seebeck coefficient, electrical resistivity, and thermal conductivity. Bi 0.5Sb 1.5Te 3 powder was synthesized using a combination of mechanical milling, calcination, and reduction processes, using a mixture of Bi 2O 3, Sb 2O 3, and TeO 2 powders. The sintered body of the oxide-reduction-synthesized Bi 0.5Sb 1.5Te 3 powder showed p-type thermoelectric characteristics. The thermoelectric properties of the sintered bodies depended on the reduction time. After being reduced for 2 h at 663 K, the sintered body of the Bi 0.5Sb 1.5Te 3 powder showed a figure of merit of approximately 1.0 at room temperature. 相似文献
4.
A liquid-phase growth process using a graphite sliding boat was applied for synthesis of p-type Bi 0.5Sb 1.5Te 3. The process lasted only 60 min, including rapid heating for melting, boat-sliding, and cooling. Thick sheets and bars of 1 mm and 2 mm in thickness having preferable crystal orientation for thermoelectric conversion were successfully prepared by the process. Control of carrier concentration was attempted through addition of excess tellurium (1 mass% to 10 mass%) to optimize the thermoelectric properties of the material. The Hall carrier concentration was found to be decreased by addition of excess tellurium. The electrical resistivity and Seebeck coefficient varied depending on the carrier concentration. As a result, the maximum observed power factor near 300 K was 4.4 × 10 ?3 W/K 2m, with corresponding Hall carrier concentration of 4.6 × 10 25 m ?3. Thus, thermoelectric properties were controllable by addition of excess tellurium, and a large power factor was thus obtained through a simple and short process. 相似文献
5.
To investigate the effects of segmentation of thermoelectric materials on performance levels, n-type segmented Bi 2Te 3/PbSe 0.5Te 0.5 thermoelectric material was fabricated, and its output power was measured and compared with those of Bi 2Te 3 and PbSe 0.5Te 0.5. The two materials were bonded by diffusion bonding with a diffusion layer that was ~18 μm thick. The electrical conductivity, Seebeck coefficient, and power factor of the segmented Bi 2Te 3/PbSe 0.5Te 0.5 sample were close to the average of the values for Bi 2Te 3 and PbSe 0.5Te 0.5. The output power of Bi 2Te 3 was higher than those of PbSe 0.5Te 0.5 and the segmented sample for small Δ T (300 K to 400 K and 300 K to 500 K), but that of the segmented sample was higher than those of Bi 2Te 3 and PbSe 0.5Te 0.5 when Δ T exceeded 300 K (300 K to 600 K and 300 K to 700 K). The output power of the segmented sample was about 15% and 73% higher than those of the Bi 2Te 3 and PbSe 0.5Te 0.5 samples, respectively, when Δ T was 400 K (300 K to 700 K). The efficiency of thermoelectric materials for large temperature differences can be enhanced by segmenting materials with high performance in different temperature ranges. 相似文献
6.
Introducing nanoinclusions in thermoelectric (TE) materials is expected to lower the lattice thermal conductivity by intensifying the phonon scattering effect, thus enhancing their TE figure of merit ZT. We report a novel method of fabricating Bi 0.5Sb 1.5Te 3 nanocomposite with nanoscale metal particles by using metal acetate precursor, which is low cost and facile to scale up for mass production. Ag and Cu particles of ??40?nm were successfully near-monodispersed at grain boundaries of Bi 0.5Sb 1.5Te 3 matrix. The well-dispersed metal nanoparticles reduce the lattice thermal conductivity extensively, while enhancing the power factor. Consequently, ZT was enhanced by more than 25% near room temperature and by more than 300% at 520?K compared with a Bi 0.5Sb 1.5Te 3 reference sample. The peak ZT of 1.35 was achieved at 400?K for 0.1?wt.% Cu-decorated Bi 0.5Sb 1.5Te 3. 相似文献
7.
The effects of applying cyclic uniaxial pressure during the pulse-current sintering process on the crystal alignment and thermoelectric properties of p-type Bi 0.5Sb 1.5Te 3 were investigated. Sintering was performed at 673 K using pulse-current heating under 70 MPa or 100 MPa of cyclic uniaxial pressure. x-Ray diffraction patterns and electron backscattered diffraction analyses showed that application of the cyclic uniaxial pressure enhanced crystal grain orientation. The texture consisted of flattened crystal grains stacked in the thickness direction of the sintered materials. The hexagonal c-plane strongly tended to align in the direction perpendicular to the uniaxial pressure. Owing to the crystal alignment, the Hall mobility in the direction perpendicular to the uniaxial pressure became larger than that of equivalent samples prepared with a constant uniaxial pressure. As a result of the increase in Hall mobility, the resistivity of the material was decreased while the equivalent Seebeck coefficient was maintained and the power factor was improved. 相似文献
8.
Two kinds of Bi 0.4Sb 1.6Te 3 powder with different particle and grain sizes were fabricated by high-energy ball milling. Powder mixtures with varied weight ratios were consolidated by vacuum hot pressing (HP) to produce nano/ microstructured composites of identical chemical composition. From measurements of the Seebeck coefficient, electrical resistivity, and thermal conductivity of these composites, a figure of merit ( ZT) value of up to 1.19 was achieved at 373 K for the sample containing 40% nanograin powder. This ZT value is higher than that of monolithic nanostructured Bi 0.4Sb 1.6Te 3. It is further noted that the ZT value of this sample in the temperature range of 450 K to 575 K is in the range of 0.7 to 1.1. Such ZT characteristics are suitable for power generation applications as no other material with a similar high ZT value in this temperature range has been observed until now. The achieved high ZT value can probably be attributed to the unique nano/microstructure, in which the dispersed nanograin powder increases the number of phonon scattering sites, which in turn results in a decrease of the thermal conductivity while simultaneously increasing the electrical conductivity, owing to the existence of the microsized powder that can provide a fast carrier transportation network. These results indicate that the nano/microstructured Bi 0.4Sb 1.6Te 3 alloy can serve as a high-performance material for application in thermoelectric devices. 相似文献
9.
Considerable research effort has gone into improving the performance of traditional thermoelectric materials such as Bi 2?x Sb x Te 3 through a variety of nanostructuring approaches. Bottom-up, chemical approaches have the potential to produce very small nanoparticles (?100?nm) with narrow size distribution and controlled shape. For this study, nanocrystalline powder of Bi 0.5Sb 1.5Te 3 was synthesized using a ligand-assisted chemical method, and consolidated into pellets with cold pressing followed by sintering in Ar atmosphere. The thermoelectric transport properties were measured from 7?K to 300?K as a function of sintering temperature. Sintering is found to increase ZT and to move the maximum in ZT to lower temperatures due to a reduction in the free charge concentration. Hall mobility studies indicate that sintering increases the electron mean free path more than it increases the phonon mean free path up to sintering temperature of 598?K. A maximum ZT of 0.42 was measured at temperature of 275?K. 相似文献
10.
The influence of the conditions for preparing samples from granules of Bi0.5Sb1.5Te3 solid solution obtained by melt solidification in liquid on the mechanical and thermoelectric properties of these samples is investigated. The microstructure and surface morphology of sample cleavages are analyzed by optical and scanning electron microscopy. The mechanical properties of the samples are investigated by compression tests at temperatures from 300 to 620 K. The thermoelectric characteristics (Seebeck coefficient and electrical and thermal conductivities) are measured both at room temperature and in the temperature range of 100–700 K. The samples with the highest thermoelectric figure of merit, (ZT)max ≈ 1.3 at 370 K, are obtained. 相似文献
11.
The effects of mechanical deformation and subsequent annealing on the thermoelectric properties and microstructure have been investigated for p-type (Bi 0.25Sb 0.75) 2Te 3 alloys prepared by melting followed by quenching. The mechanically deformed pellets were prepared by repetition of cold-pressing of quenched samples at room temperature. Cold-pressed pellets were then annealed at 300°C in vacuum, and the thermoelectric properties and microstructure were traced through the course of the heat treatment. For the heavily deformed samples, the Seebeck coefficient rapidly increased at the very early stage of annealing and did not change as the annealing time increased, due to recrystallization of a new δ-phase which equilibrated at the annealing temperature of 300°C (δ 300-phase). At the initial stage of annealing (recovery stage), the electrical resistivity sharply increased, probably due to the interaction of antistructural defects with vacancies produced during the cold-pressing treatment. However, for the lightly deformed samples, recrystallization occurred only at some portion of the grain boundaries, and the newly generated δ 300-phase slowly replaced the original, as-solidified δ ingot-phase. 相似文献
12.
In this work, it is found that unique pillar arrays with nanolayered structure can favorably influence the carrier and phonon transport properties of films. p-(Bi 0.5Sb 0.5) 2Te 3 pillar array film with (0 1 5) orientation was successfully achieved by a simple ion-beam-assisted technique at deposition temperature of 400°C, owing to the enhanced mobility of deposited atoms for more sufficient growth along the in-plane direction. The pillar diameter was about 250 nm, and the layered nanostructure was clear, with each layer in the pillar array being <30 nm. The properties of the oriented (Bi 0.5Sb 0.5) 2Te 3 pillar array were greatly enhanced in comparison with those of ordinary polycrystalline films synthesized at deposition temperature of 350°C and 250°C. The (Bi 0.5Sb 0.5) 2Te 3 pillar array film with (0 1 5) preferred orientation exhibited a thermoelectric dimensionless figure of merit of ZT = 1.25 at room temperature. The unique pillar array with nanolayered structure is the main reason for the observed improvement in the properties of the (Bi 0.5Sb 0.5) 2Te 3 film. 相似文献
13.
In this work, p-type nanoscale ??soft superlattices?? consisting of multilayer stacks of 25?nm Sb 2Te 3 on 25?nm (Bi 0.2Sb 0.8) 2Te 3 were fabricated by nanoalloying. With this technique, nanoscale layers of the elements Bi, Sb, and Te are deposited by sputtering onto a Si/SiO 2 substrate and subsequently annealed to induce interdiffusion and a solid-state reaction to form the final superlattices. Different combinations of annealing temperatures were used in the annealing process. The in-plane electronic properties (Seebeck coefficient, electrical conductivity, charge carrier concentration, and carrier mobility) of these soft superlattices were examined. The cross-plane thermal conductivity was determined using time-domain thermal reflectance (TDTR). Secondary-ion mass spectrometry (SIMS) depth profiles reveal that the nanostructured thin films exhibit high stability against thermal interdiffusion during the annealing process. X-ray patterns of the samples display very strong texture with preferred c-orientation of the crystallites after the heat treatment. Scanning electron microscopy (SEM) cross-section images of the films show distinctly polycrystalline structure with increasing grain size for higher annealing temperatures, as confirmed by x-ray diffraction (XRD) analysis. Very high power factors exceeding 40? ??W/cm?K 2, similar to values for bulk single crystals with comparable compositions, are observed for the soft superlattices. The nanostructure appears to be stable up to 300°C. For a sample annealed at 150°C, a thermal conductivity as low as 0.45?W/mK was determined. Based on different assumptions concerning the degree of anisotropy of the transport properties, a cross-plane figure of merit ZT of 0.6 to 1.9 can be estimated for the thin films annealed at 300°C. 相似文献
14.
A series of p-type Ba 0.3In 0.3FeCo 3Sb 12/Bi 0.48Sb 1.52Te 3 (FS/BT) thermoelectric (TE) materials containing one gradient layer (1GL) with FS/BT volume ratio of 5:5, 3GLs-I with 7:3–5:5–3:7, 3GLs-II with 3:7–5:5–7:3, and 3GLs-III with 3:7–5:5–3:7 from FS to BT were fabricated by a two-step spark plasma sintering method. The interface structure and mechanical properties of the p-type FS/BT TE materials were investigated in this work. Designing the GLs at the interface of FS and BT bulk TE materials can effectively relax the thermal stress induced by the large difference in thermal expansion coefficient and eliminate the macroscopic cracks that occur in FS/BT TE materials with no GL, hence resulting in a remarkable enhancement in the interface mechanical properties of the FS/BT TE materials with the GLs. The optimized gradient interface of the FS/BT TE materials is 3GLs-II with FS/BT volume ratio of 3:7–5:5–7:3. The highest flexural strength of the 3GLs-II sample reached 13.68 MPa, increased by 116%. 相似文献
16.
This work focused on the preparation of p-type Bi 0.4Sb 1.6Te 3 bulk materials by combining mechanical alloying (MA) and hot extrusion, with emphasis on grain refinement and preferred grain orientation. Pure Bi, Sb, and Te powders were mechanically alloyed then hot extruded in the temperature range 360–450°C. Bi 0.4Sb 1.6Te 3 bulk materials were successfully prepared by MA and hot extrusion. All the samples had sound appearance, with single phases and high densities. The hot-extruded samples had small grain sizes, and the lower the extrusion temperature, the smaller the grain sizes. The results indicated that the extrudates had preferred orientation. The basal plane was predominantly oriented parallel to the direction of extrusion. Similar Seebeck coefficients were obtained when extrusion temperature was in the range 380–420°C. Electrical resistivity decreased with increasing extrusion temperature. Thermal conductivity was relatively low, even if the extrusion temperature was 450°C. As a result, a ZT value of 1.2 was obtained at room temperature for the sample extruded at 400°C. Therefore, combination of MA and hot extrusion results in significant improvement of both the thermoelectric and mechanical performance of Bi 0.4Sb 1.6Te 3 bulk materials. 相似文献
17.
A comparative analysis of structures of compact samples of Bi 0.5Sb 1.5Te 3 thermoelectric materials, obtained by the spark plasma sintering (SPS) and traditional hot-pressing methods, was performed by the X-ray diffractometry and scanning electron microscopy methods. It is shown that the spark plasma sintering method failed to obtain structure sizes smaller than the hot-pressing method. However, the sintering quality, characterized by the absence of pores and cracks, and sizes of fragments of the fractured surface, is higher at comparable temperatures in the samples obtained by the SPS-method. 相似文献
18.
Since the 1960s, the TAGS system, namely (GeTe) x (AgSbTe 2) 1?x , with two specific compositions x = 0.8 and 0.85, known as TAGS-80 and TAGS-85, respectively, was identified as containing highly efficient p-type thermoelectric materials. Recently, another highly efficient p-type GeTe-rich composition, namely 3% Bi 2Te 3-doped Ge 0.87Pb 0.13Te, achieving thermoelectric properties comparable to TAGS-based solid solutions, was also reported. Since all of these compositions were obtained by different manufacturing approaches, a comparison between the transport and mechanical properties of these alloys, prepared by the same manufacturing techniques, is required to identify the advantages and disadvantages of these compositions for practical thermoelectric applications. In the current research, the thermoelectric and mechanical properties of three highly efficient GeTe-rich alloys, TAGS-80, TAGS-85, and 3% Bi 2Te 3-doped Ge 0.87Pb 0.13Te, following hot pressing, were investigated and compared. Maximal ZT values of ~1.75, ~1.4, and ~1.6 at 500°C were found for these compositions, respectively. Improvement of the mechanical properties was observed by increasing the GeTe content. The influence of the GeTe relative amount on the transport and mechanical properties was interpreted by means of the phase-transition temperatures from the low-temperature rhombohedral to the high-temperature cubic phases. 相似文献
19.
Semiconductors - Antimony-telluride-based nanocomposite samples containing different weight fractions of graphite (Sb2Te3 + x% graphite, where x = 0.0, 0.5, 1.0, and 2.5%) are synthesized and... 相似文献
20.
Bismuth-telluride-based alloy is the sole thermoelectric candidate for commercial thermoelectric application in low-grade waste heat harvest near room temperature, but the sharp drop of thermoelectric properties at higher temperature and weak mechanical strength in zone-melted material are the main obstacles to its wide development for power generation. Herein, an effective approach is reported to improve the thermoelectric performance of p-type Bi 0.42Sb 1.58Te 3 hot-pressed sample by incorporating Ag 5SbSe 4. A peak ZT of 1.40 at 375 K and a high average ZT of 1.25 between 300 and 500 K are achieved. Such outstanding thermoelectric performance originates from the synergistic effects of improved density-of-states effective mass, reduced bipolar thermal conductivity by the boosted carrier concentration, and suppressed lattice thermal conductivity by the induced phonon scattering centers including substitute point defects, dislocations, stress–strain clusters, and grain boundaries. Comprised of the p-type Bi 0.42Sb 1.58Te 3 + 0.10 wt% Ag 5SbSe 4 and zone-melted n-type Bi 2Te 2.7Se 0.3, the thermoelectric module exhibits a high conversion efficiency of 6.5% at a temperature gradient of 200 K, indicating promising applications for low-grade heat harvest near room temperature. 相似文献
|