Showing papers on "Antimony telluride published in 2012"
TL;DR: The possibility of engineering multiphases to further improve thermoelectric performance beyond phonon scattering through a low-temperature solution processed route is shown.
Abstract: In this work, Ag(x)Te(y)-Sb(2)Te(3) heterostructured films are prepared by ligand exchange using hydrazine soluble metal chalcogenide. Because of the created interfacial barrier, cold carriers are more strongly scattered than hot ones and thereby an over 50% enhanced thermoelectric power factor (~2 μW/(cm·K(2))) is obtained at 150 °C. This shows the possibility of engineering multiphases to further improve thermoelectric performance beyond phonon scattering through a low-temperature solution processed route.
94 citations
TL;DR: Density functional theory calculations indicate that sulfur increases the antisite formation activation energy and presage further improvements leading to ZT ∼ 2 through optimized doping, which are promising for designing novel thermoelectric materials for refrigeration, waste heat recovery, and solar thermal applications.
Abstract: Antimony telluride has a low thermoelectric figure of merit (ZT < ∼0.3) because of a low Seebeck coefficient α arising from high degenerate hole concentrations generated by antimony antisite defects. Here, we mitigate this key problem by suppressing antisite defect formation using subatomic percent sulfur doping. The resultant 10–25% higher α in bulk nanocrystalline antimony telluride leads to ZT ∼ 0.95 at 423 K, which is superior to the best non-nanostructured antimony telluride alloys. Density functional theory calculations indicate that sulfur increases the antisite formation activation energy and presage further improvements leading to ZT ∼ 2 through optimized doping. Our findings are promising for designing novel thermoelectric materials for refrigeration, waste heat recovery, and solar thermal applications.
82 citations
TL;DR: In this paper, a systematic optimization of p-type Sb2Te3 thermoelectric films made by potentiostatic electrodeposition on Au and stainless steel substrates is presented.
Abstract: A systematic optimization of p-type Sb2Te3 thermoelectric films made by potentiostatic electrodeposition on Au and stainless steel substrates is presented. The influence of the preparative parameters of deposition voltage, concentration, and the deposition method are investigated in a nitric acid solution. As a postdeposition step, the influence of annealing the films is investigated. The use of a potential-controlled millisecond-pulsed deposition method could improve both the morphology and the composition of the films. The samples are characterized in terms of composition, crystallinity, Seebeck coefficient, and electrical resistivity. Pulsed-deposited films exhibit Seebeck coefficients of up to 160 mu V K-1 and an electrical conductivity of 280 S cm-1 at room temperature, resulting in power factors of about 700 mu W m-1 K-2. After annealing, power factors of maximum 852 mu W m-1 K-2 are achieved. Although the annealing of DC-deposited films significantly increased the power factor, they do not reach the values of the pulsed-deposited films in the preannealing state. Structural analysis is performed with X-ray diffraction and shows the crystalline structure of Sb2Te3 films. The performance is tuned by annealing of deposited films up to 300 degrees C under He atmosphere while performing in-situ X-ray diffraction and resistivity measurements. The chemical analysis of the films is performed by inductively coupled plasma optical emission spectroscopy (ICP-OES) as well as scanning electron microscope energy dispersive X-ray analysis (SEM-EDX).
65 citations
TL;DR: Using the angle-dispersive synchrotron x-ray powder diffraction technique in a diamond anvil cell, the high-pressure behaviors of antimony telluride are explored up to 52.7 GPa at room temperature and the metallic character for β-, γ- and δ-Sb(2)Te(3) increases in turn based on the results of the electronic density of states calculated for each high- pressure phase.
Abstract: Using the angle-dispersive synchrotron x-ray powder diffraction technique in a diamond anvil cell, the high-pressure behaviors of antimony telluride (Sb2Te3) are explored up to 52.7 GPa at room temperature. Three high-pressure phases have been observed, at about 8.0 GPa, 13.2 GPa and above 21.6 GPa, respectively. Furthermore, the crystalline structures of these high-pressure phases are determined as monoclinic sevenfold C2/m phase, eightfold C2/c phase and disordered body-centered cubic structure (space group Im - 3m) respectively. The phase-transition sequences and pressures observed are well explained by first-principles calculations. The pressure dependence of the volume of all high-pressure phases is described by a third-order Birch-Murnaghan equation of state. All the high-pressure phases are metallic and the metallic character for beta-, gamma- and delta-Sb2Te3 increases in turn based on the results of the electronic density of states calculated for each high-pressure phase.
51 citations
TL;DR: In this paper, the size-selective synthesis of hexagonal Sb2Te3 nanoplates by thermal decomposition of the single-source precursor bis(diethylstibino)telluride (Et2Sb)2Te is described for the first time.
Abstract: The size-selective synthesis of hexagonal Sb2Te3 nanoplates by thermal decomposition of the single-source precursor bis(diethylstibino)telluride (Et2Sb)2Te is described for the first time. The role of the thermolysis temperature and the concentration of the capping agent (PVP*) on the growth of the nanoplates was investigated. The thermal properties of (Et2Sb)2Te were investigated by differential scanning calorimetry (DSC), and the resulting Sb2Te3 nanoplates were characterized by XRD, SEM, TEM, EDX, and SAED. Moreover, electrical conductivity, Seebeck coefficient and thermal conductivity of the nanoplates were determined, clearly proving the enhanced thermoelectric properties of nanosized antimony telluride.
48 citations
TL;DR: In this paper, the authors present experimental evidence of enhancement of thermoelectric properties in tellurium (Te) nanoparticle-embedded bismuth antimony telluride (BiSbTe) alloys.
Abstract: We present experimental evidence of enhancement of thermoelectric properties in tellurium (Te) nanoparticle-embedded bismuth antimony telluride (BiSbTe) alloys. Bi0.5Sb1.5Te3 films with a high density of Te particles of 10–20 nm size were prepared by growth of alternating multilayers of ultrathin Te and Bi0.5Sb1.5Te3. As the amount of Te nanoinclusions increased up to ∼15%, the Seebeck coefficient and thermoelectric power factor were increased. Based on the concept of band bending at heterointerfaces as a carrier energy filter, the energy relaxation calculation was made to confirm that the Te nanoinclusions result in a carrier energy filtering effect in p-type bismuth antimony telluride. In addition, thermal conductivities were reduced in the Te-embedded samples, permitting possible further enhancement of the thermoelectric figure of merit. The advantages of Te nanoinclusions in p-type Bi0.5Sb1.5Te3alloys on thermoelectric performance are experimentally realized by both electron- and phonon scattering.
22 citations
TL;DR: In this article, the effects of substrate temperature on the structure, surface morphology, and thermoelectric properties of the thin films were investigated, and the results showed that a temperature of 250°C resulted in stoichiometric Sb2Te3, which exhibited the maximum Seebeck coefficient of 190μV/K and the lowest power factor (PF) of 8.75×10−5 W/mK2.
Abstract: Antimony and tellurium were deposited on BK7 glass using direct-current magnetron and radiofrequency magnetron cosputtering. Antimony telluride thermoelectric thin films were synthesized with a heated substrate. The effects of substrate temperature on the structure, surface morphology, and thermoelectric properties of the thin films were investigated. X-ray diffraction patterns revealed that the thin films were well crystallized. c-Axis preferred orientation was observed in thin films deposited above 250°C. Scanning electron microscopy images showed hexagonal crystallites and crystal grains of around 500 nm in thin film fabricated at 250°C. Energy-dispersive spectroscopy indicated that a temperature of 250°C resulted in stoichiometric Sb2Te3. Sb2Te3 thin film deposited at room temperature exhibited the maximum Seebeck coefficient of 190 μV/K and the lowest power factor (PF), S
2
σ, of 8.75 × 10−5 W/mK2. When the substrate temperature was 250°C, the PF increased to its highest value of 3.26 × 10−3 W/mK2. The electrical conductivity and Seebeck coefficient of the thin film were 2.66 × 105 S/m and 113 μV/K, respectively.
20 citations
TL;DR: In this article, the p-type antimony telluride (Sb2Te3) pillar arrays with unique hierarchical architecture have been self-assembled in large scale by a simple vacuum thermal evaporation technique.
Abstract: The p-type antimony telluride (Sb2Te3) pillar arrays with unique hierarchical architecture have been self-assembled in large scale by a simple vacuum thermal evaporation technique. The composition and the microstructure of the films are studied by X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, and high-resolution transmission electron microscopy. The results show that the hierarchical film with multi-scale and multi-dimensional structure is well-oriented pillar arrays perpendicular to the substrate. A large number of nanowires (NWs) are assembled into a submicro/micro-scaled pillar, while antisite defects and dislocations as well as other defects are found in the one-dimensional NWs. The growth mechanism of such nanostructure is proposed and investigated. The thermoelectric (TE) properties, i.e., electrical conductivity (σ), Seebeck coefficient (S), and thermal conductivity (κ) of the films are measured. The properties of the hierarchical Sb2Te3 film have been greatly enhanced in comparison with those of the ordinary Sb2Te3 films. A TE dimensionless figure-of-merit ZT = 0.88 in the novel hierarchical Sb2Te3 film is obtained at room temperature.
19 citations
TL;DR: In this paper, an aqueous chemical synthesis of bismuth telluride Bi2Te3 and other chalcogenide thermoelectric materials is presented, where powders from the reactions are sintered to give nanocomposites using spark plasma sintering.
Abstract: Chemical synthesis of bismuth telluride Bi2Te3 and other chalcogenide thermoelectric materials is possible by many different routes. Most often, the chalcogenide material is produced as nanocrystals of various morphologies in attempts to achieve better thermoelectric performance in the nanocomposite because of enhanced grain boundary scattering. However, publications dealing with the synthesis of large amounts of cheap nanomaterials are still very rare. We present an aqueous chemical synthesis in alkaline solution as well as in an NH3/NH4Cl buffer medium producing nanocrystalline bismuth telluride in high quantities. For the precipitation process, different Bi and Sb salts can be used as precursors resulting in a variety of product morphologies. The use of a buffer medium for the reaction solution makes it possible to dissolve the precursors in acidic medium, adding a solution instead of dispersion to the reaction medium. The powders from the reactions were sintered to give nanocomposites using spark plasma sintering. Only a small influence of sintering on the nanostructure could be detected. Room-temperature thermoelectric properties of these nanocomposites are within the range or slightly worse than the values for bulk material.
17 citations
TL;DR: In this article, the effects of synthesis conditions on the resulting microstructure and compositional homogeneity were investigated using x-ray diffraction, electron diffraction and electron microscopy.
14 citations
TL;DR: The C-AFM data show that the electrical conductivity of nanosized grains is higher than the bulk value and reaches 1600 S cm(-1), which results in a moderate increment of the overall electrical Conductivity, thereby increasing the figure of merit (ZT) up to 1.4 at 100 °C.
Abstract: In order to explain the unique thermoelectric properties of bulk nanocomposite p-type bismuth antimony telluride, its structural and electrical properties are investigated using transmission electron microscopy (TEM) and atomic force microscopy with a conductive probe (C-AFM). The material is observed to contain both nano- and micro-sized grains with sizes varying from 10 nm to 3 µm. This unique structure promotes phonon scattering, thereby decreasing the thermal conductivity to below 1 W mK−1 at room temperature. Moreover, the C-AFM data show that the electrical conductivity of nanosized grains is higher than the bulk value and reaches 1600 S cm−1. This results in a moderate increment of the overall electrical conductivity, thereby increasing the figure of merit (ZT) up to 1.4 at 100 °C. In addition to demonstrating a powerful scanning probe microscopy (SPM) based investigation technique that requires minimal sample preparation, our findings contribute towards better understanding of the enhancement of thermoelectric properties of nanocomposite thermoelectric materials.
TL;DR: In this article, single-crystalline and highly pure antimony telluride (Sb2Te3) nanoflakes have been synthesized via simple wet chemical route at 70°C for 8h, in which hydrazine hydrate plays as an important solvent.
Dissertation•
01 Jan 2012
TL;DR: In this paper, the authors propose a novel approach to solve the problem of homonymity in homophily, and propose a solution to homophysics, which works well.
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TL;DR: In this paper, organic-assisted antimony telluride nanorods were successfully fabricated by a simple hydrothermal method by means of X-ray diffraction, scanning electron microscope, and transmission electron microscope.
Abstract: Nano-sized antimony telluride is of much interest for improving the thermoelectric figure of merit. In the present work, organic-assisted antimony telluride nanorods were successfully fabricated by a simple hydrothermal method. The products were characterized by means of X-ray diffraction, scanning electron microscope, and transmission electron microscope. The results show that the typical antimony telluride synthesized by co-precipitation reductive route is rodlike in shape with about 35 nm in thickness and 300 nm in edge length.
TL;DR: In this article, a hollow nanosphere antimony telluride (nano-Sb2Te3) was fabricated with antimony (Sb and Te) vapors via a fast and facile a thermal evaporation process.
Patent•
08 Aug 2012
TL;DR: In this article, a cadmium telluride thin-film solar cell back contact layer was produced in the vacuum environment, where a vertical coater was used to simultaneously coat both sides of the substrate, enlarge the effective region of the coating and increase the production efficiency.
Abstract: The invention discloses a cadmium telluride thin-film solar cell back contact layer production method, and the production process is carried out in the vacuum environment The steps are as follows: a substrate is preheated to 160 DEG C to 220 DEG C; after the substrate is heated to 230 DEG C to 320 DEG C, the magnetron sputtering of antimony telluride is carried out; after the substrate is cooled to 80 DEG C to 120 DEG C, the sputtering of nickel-vanadium alloy is carried out; and the substrate is cooled to less than 70 DEG C and then discharged The coating of a cadmium telluride thin-film solar cell back contact layer produced by the method is uniform, and the number of pinholes is less The invention also discloses a vertical coater which adopts the method to produce cadmium telluride thin-film solar cell back contact layers, the vertical coater comprises but is not limited to a preheating chamber, a temperature-keeping antimony telluride deposition chamber, a nickel-vanadium alloy deposition chamber, a temperature-decreasing discharge chamber, a vacuum system and the like which are connected in series through vacuum valves, and the vertical coater can simultaneously coat both sides of the substrate, enlarge the effective region of the coating and increase the production efficiency, and is easy to overhaul
TL;DR: In this article, a spark plasma sintering process was used to obtain high density bulk Bismuth antimony telluride (BiSbTe) thermoelectric materials.
Abstract: Bismuth antimony telluride (BiSbTe) thermoelectric materials were successfully prepared by a spark plasma sintering process. Crystalline BiSbTe ingots were crushed into small pieces and then attrition milled into fine powders of about 300 nm ~ 2 size under argon gas. Spark plasma sintering was applied on the BiSbTe powders at 240, 320, and , respectively, under a pressure of 40 MPa in vacuum. The heating rate was /min and the holding time at the sintering temperature was 10 min. At all sintering temperatures, high density bulk BiSbTe was successfully obtained. The XRD patterns verify that all samples were well matched with the . Seebeck coefficient (S), electric conductivity () and thermal conductivity (k) were evaluated in a temperature range of . The thermoelectric properties of BiSbTe were evaluated by the thermoelectric figure of merit, ZT (ZT
TL;DR: In this paper, micro/nano-structured Bi0.5Sb1.5Te3bulk thermoelectric materials were synthesized by mechanical alloying from elemental shots of Bi, Sb, and Te.
Abstract: In this work, micro/nano-structured Bi0.5Sb1.5Te3bulk thermoelectric materials were synthesized by mechanical alloying from elemental shots of Bi, Sb, and Te. Cold pressing and subsequent heat treatments with hydrogen reduction were used to form bulk solid samples with good thermoelectric properties in the temperature range around 75℃to 100℃. In comparison to crystal growth methods and chemical solution synthesis, the reported technique can be readily implemented for mass production with relatively low cost.
TL;DR: In this article, a low-cost micro-thermoelectric generator (μ-TEG) is proposed, which can be fabricated by using electrochemical and MEMS technology.
Abstract: This paper presents a new way to design a low-cost micro-thermoelectric generator (μ-TEG) which can be fabricated by using electrochemical and MEMS technology. The overall dimension of the μ-TEG is about 13mm × 13mm × 0.4mm, which contains 128 p- and n-type pairs of semiconductors connected electrically in series and thermally in parallel. The p-type antimony telluride (Sb2Te3) and n-type bismuth telluride (Bi2Te3) with an optimal thickness of 20μm were designed to deposit in a flexible polymer mold formed by photolithographic patterning of Polyimide (PI) with a three electrode configuration. Simulations of the thermocouple with PI mold were carried on, using finite element analysis. The analysis shows the possibility to achieve 3.5 mV while the difference in temperature is 10K and the thickness of the silicon substrate is 400μm, which reveals that the output power of the thermocouple without releasing process is only 4% lower than the one with the releasing process. Therefore the PI mold is not removed, considering the potential for easier fabrication and lower cost. The deposition parameters were also studied and optimized for the best thermoelectric performance. In our experiments, the n- and p-type semiconductors could be obtained when the voltage and current are around 50mV versus saturated calomel electrode (SCE) and 40 mA, respectively.
Patent•
19 Sep 2012
TL;DR: A phase change storage device based on an antimony telluride composite phase change material and a preparation method belonging to the field of computer technology was proposed in this article. But the phase change device was not used for data storage.
Abstract: The invention relates to a phase change storage device based on an antimony telluride composite phase change material and a preparation method thereof, belonging to the field of computer technology. The device comprises a substrate, a lower electrode, a heat generation electrode layer, an insulating layer, a phase change material layer and an upper electrode, wherein the phase change material layer is a composite phase change material layer containing antimony telluride and silicon nitride; the atom percent content range of the silicon nitride is 0.5-30; and the proportional range of Sb atomsand Te atoms in the phase change material layer is 80/20-30/70. The composite phase change material layer which has high crystallization velocity and higher heat generation efficiency is used by the phase change storage device of the invention, thus the operation velocity of the phase change storage device can be improved, and the RESET operation current of the phase change storage device can be lowered.
01 Jan 2012
TL;DR: In this paper, a cationic exchange reaction of thermally evaporated antimony telluride thin films was used to synthesize tailored compositions of thin films with tailored compositions.
Abstract: Ternary silver antimony telluride (AgxSb1−xTey) thin films with tailored compositions were synthesized by a cationic exchange reaction of thermally evaporated antimony telluride thin films, as a simple and costeffective approach. The composition of AgxSb1−xTey thin films was controlled by the reaction time. Temperaturedependent electrical properties of the AgxSb1−xTey thin films demonstrated phase transition behavior from 323 K to 343 K. The composition-dependent thermoelectric properties (i.e., electrical resistivity (ρ), Seebeck coefficient (S) and power factor (S2ρ)) of the as-deposited Sb54Te46, the transformed AgxSb1−xTey and the annealed AgxSb1−xTey thin films were investigated as a function of temperature.
01 Jan 2012
TL;DR: In this paper, a planar thermoelectric generator was fabricated on a silicon-on-insulator (SOI) substrate with a FinFET-based CMOS (complementary metal oxide semiconductor).
Abstract: This paper presents the fabrication of bismuth telluride (Bi 2Te 3) and antimony telluride (Sb 2Te 3) thin film-based thermoelectric harvesters on silicon-on-insulator (SOI) substrate with FinFET (field-effect transistor) based CMOS (complementary metal oxide semiconductor). These films can be used to integrate planar thermoelectric generators (TEG) or thermoelectric coolers (TEC) directly with CMOS circuits. The thermoelectric films are deposited by co-evaporation through shadow-masks in a post-CMOS process, with improved contact resistance via pre-deposition surface treatments. Transistor performance showed no significant change upon TEG fabrication, indicating CMOS compatibility of the thermoelectric thin film deposition process. A 2.14 ×2.14-mm 2 sized square-shaped planar thermoelectric harvester has been fabricated as a demonstration vehicle and generates 0.67 µW from a temperature gradient of 21 K, with an average open circuit output of 233 µV/K per thermocouple.
01 Jan 2012
TL;DR: In this article, the p-type antimony telluride (Sb2Te3) pillar arrays with unique hierarchical architecture have been self-assembled in large scale by a simple vacuum thermal evaporation technique.
Abstract: The p-type antimony telluride (Sb2Te3) pillar arrays with unique hierarchical architecture have been self-assembled in large scale by a simple vacuum thermal evaporation technique. The composition and the microstructure of the films are studied by X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, and high-resolution transmission electron microscopy. The results show that the hierarchical film with multi-scale and multi- dimensional structure is well-oriented pillar arrays perpendicular to the substrate. A large number of nanowires (NWs) are assembled into a submicro/ micro-scaled pillar, while antisite defects and dislo- cations as well as other defects are found in the one- dimensional NWs. The growth mechanism of such nanostructure is proposed and investigated. The ther- moelectric (TE) properties, i.e., electrical conductivity (r), Seebeck coefficient (S), and thermal conductivity (j) of the films are measured. The properties of the hierarchical Sb2Te3 film have been greatly enhanced in comparison with those of the ordinary Sb2Te3 films. A TE dimensionless figure-of-merit ZT = 0.88 in the novel hierarchical Sb2Te3 film is obtained at room temperature.