Bismuth Antimony Telluride Research Articles

Integrating dual heat sources to enhance thermoelectric generator power output

The escalating demand for sustainable power sources for wearable electronics necessitates innovative solutions. This study tackles the challenge of sustainably powering wearable electronics, addressing the limitations of traditional batteries. The approach utilizes a thermoelectric generator with a flexible and stretchable substrate that integrates the photothermal effect and human body temperature as a heat source. A unique strategy is employed to achieve this, involving the combination of 10 g of polydimethylsiloxane, 0.5 g of carbon nanotubes powder, 1 g of base curing agent, and 1.15 g of ethyl acetate mixture used as the novel substrate material. The proposed composite substrate is paired with p-type and n-type thermoelectric legs of bismuth antimony telluride (Bi0.4Sb1.6Te3) and bismuth selenium telluride (Bi1.7Te3.7Se0.3), respectively. This innovative design ensures high flexibility, stretchability, and conformability, facilitating seamless integration into wearable electronic devices. Experimental validation and simulation-based studies reveal a power density of 166.29 μW/cm2, sufficient for powering small-scale wearable electronics. The thermoelectric generator coupled with a novel composite substrate showed 65.6 % stretchability, further underscoring its durability and adaptability. The critical finding lies in the dual heat source integration, which collectively boosts power output and ensures year-round performance, pushing the boundaries of wearable energy harvesting technologies.

Fabrication of Bi2Te3 and Sb2Te3 Thermoelectric Thin Films using Radio Frequency Magnetron Sputtering Technique.

Through various studies on thermoelectric (TE) materials, thin film configuration gives superior advantages over conventional bulk TEs, including adaptability to curved and flexible substrates. Several different thin film deposition methods have been explored, yet magnetron sputtering is still favorable due to its high deposition efficiency and scalability. Therefore, this study aims to fabricate a bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3) thin film via the radio frequency (RF) magnetron sputtering method. The thin films were deposited on soda lime glass substrates at ambient temperature. The substrates were first washed using water and soap, ultrasonically cleaned with methanol, acetone, ethanol, and deionized water for 10 min, dried with nitrogen gas and hot plate, and finally treated under UV ozone for 10 min to remove residues before the coating process. A sputter target of Bi2Te3 and Sb2Te3 with Argon gas was used, and pre-sputtering was done to clean the target's surface. Then, a few clean substrates were loaded into the sputtering chamber, and the chamber was vacuumed until the pressure reached 2 x 10-5 Torr. The thin films were deposited for 60 min with Argon flow of 4 sccm and RF power at 75 W and 30 W for Bi2Te3 and Sb2Te3, respectively. This method resulted in highly uniform n-type Bi2Te3 and p-type Sb2Te3 thin films.

Structural, optical, and electrical analysis of tailoring Bi2-xSbxTe3 thin films

Bismuth antimony telluride (Bi2-xSbxTe3) thin films were synthesized using chemical bath deposition (CBD) with various amounts of antimony. The structural, morphological, and optical properties of Bi2-xSbxTe3 thin films have been scrutinized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), UV-Vis spectrophotometry. A higher amount of Sb contents can be observed the Sb0.405Te0.595, BiTe, and Bi4Te3 phases consisted in the pattern. Meanwhile, the energy band gaps are tuned in the range of 2.95 to 3.30 eV. Finally, measurement of resistance with various temperatures for activation energy (EAC) estimation was performed. The highest EAC value was equal to 0.654 eV for 0.8 g SbCl3 as a precursor of Sb atom incorporated in the Bi2Te3 lattice.

Enhancing the thermoelectric properties of bismuth antimony tellurides containing excess Te with respect to sintering temperature

Bi–Te-based thermoelectric materials with excellent room-temperature properties are difficult to commercialise because of their low dimensionless figure of merit ( ZT). In this study, a powder was synthesised by adding an excess amount of Te to improve its thermoelectric performance at room temperature. The synthesised powder was sintered using spark plasma sintering at various temperatures to examine the effect of temperature-dependent behaviour of Te on the electrical resistivity and Seebeck coefficient. The excess Te-containing powder exhibited excellent electrical conductivity and Seebeck coefficient at high temperatures, and the thermal conductivity was significantly reduced. Bi0.4Sb1.6Te3+ x ( x = 2) showed a maximum room-temperature ZT of 1.57 at a sintering temperature of 450°C.

Development of a Topological-Insulator-Based Quantum Resistance Standard.

This paper describes the characterization of the quantum anomalous Hall (QAH) effect resistor with Chromium-doped Bismuth Antimony Telluride with the efforts in coupling directly to a programmable Josephson voltage standard (PJVS) at zero magnetic field. The precision measurement of the QAH resistance was performed under the presence of microwave signal biased to the PJVS. Understanding such effect will help to improve the experimental set-up for integrating multiple quantum electrical standards in a single system.

Achieving thermoelectric performance of rGO/Bi0.5Sb1.5Te3/Cu2Se1–xTex composites through the scattering engineering strategy

Bismuth antimony telluride (Bi2–xSbxTe3) is commonly used for thermoelectric generation at temperatures near ambient temperature. Here, we report incorporating reduced graphene oxide (rGO) and Cu2Se0.98Te0.02 into theBi0.5Sb1.5Te3 (BST) (rGO/Bi0.5Sb1.5Te3-xCu2Se0.98Te0.02, where x = 0.0%, 0.1%, 0.3%, 0.5% and 1.0%, in mass) synthesized by a solid-state technique. The dispersion of rGO and Cu2Se0.98Te0.02 into the BST matrix improved carrier transport properties at the grain boundary interfaces and reduced thermal conductivity. Strong electron scattering at large interface barriers was responsible for increased electrical conductivity. The bulk sample of rGO/BST-0.3% Cu2Se0.98Te0.02 (in mass) possessed a low thermal conductivity of 0.76 W·m−1·K−1 at 497 K. Enhanced phonon scattering at grain boundaries between BST and rGO/Cu2Se0.98Te0.02 caused a low thermal conductivity. At 448 K, the highest zT value for rGO/BST-0.3%Cu2Se0.98Te0.02 (in mass) was 1.64, which is 37% higher than the zT value for pure BST (zT = 1.19). Results suggested that incorporating rGO and Cu2Se0.98Te0.02 into the BST matrix effectively improved thermoelectric power generation.

Thermoelectric Properties of Polyaniline/Bismuth Antimony Telluride Composite Materials Prepared via Mechanical Mixing

Organic-based thermoelectric composites are highly promising for low-temperature heat-to-electrical energy conversion applications due to their low toxicity, cost-effectiveness, facile synthesis and easy processing. Potential applications of such materials include, among others, low-temperature waste heat recovery and body heat use, such as wearable thermoelectric devices and sensors. Due to the lack of studies on organic (matrix)–inorganic (additive) thermoelectric composites prepared via mechanical mixing with respect to the processing parameters and thermoelectric performance, this work aims to contribute in this direction. More precisely, composite pellets were prepared starting from polyaniline (PANI)/bismuth antimony telluride mixed powders using a mechanical press. The processing parameters investigated included temperature, pressure and processing time, along with the inorganic additive (bismuth antimony telluride) content introduced within the composites. The experimental data revealed that the processing temperature and the additive content had the most significant effect, since their increase led to an enhancement in the composites’ thermoelectric performance. The optimal ZT (2.93 × 10−3) recorded at 130 ∘C corresponded to PANI-BST composites with a 30 wt.% BST content, prepared at a processing temperature of 80 ∘C, a processing time of 75 min and under 2 tons of pressure.

Interference, diffraction, and diode effects in superconducting array based on bismuth antimony telluride topological insulator

It is well-known in optics that the spectroscopic resolution of a diffraction grating is much better compared to an interference device having just two slits, as in Young’s famous double-slit experiment. On the other hand, it is well known that a classical superconducting quantum interference device (SQUID) is analogous to the optical double-slit experiment. Here we report experiments and present a model describing a superconducting analogue to the diffraction grating, namely an array of superconducting islands positioned on a topological insulator film Bi0.8Sb1.2Te3. In the limit of an extremely weak field, of the order of one vortex per the entire array, such devices exhibit a critical current peak that is much sharper than the analogous peak of an ordinary SQUID. Therefore, such arrays can be used as sensitive absolute magnetic field sensors. A key finding is that the device acts as a superconducting diode, controlled by magnetic field.

Continuous and Intermittent Planetary Ball Milling Effects on the Alloying of a Bismuth Antimony Telluride Powder Mixture

This study investigates the effects of continuous and in-steps mechanical alloying of a bismuth antimony telluride powder mixture (Bi0.4Sb1.6Te3.0) via the mechanical planetary ball milling (PBM) process as a function of milling time and powder mixture amount. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the phase, composition, and morphology of the alloy. The alloyed powder with the optimum PBM conditions was then hot pressed (HP), and its thermoelectric properties were further investigated. The results on the alloying of the powder mixture showed that due to the high agglomeration tendency of BST during the PBM process, a significant deviation occurs in the development of a single-phase state over time when the powder mixture is milled continuously and in-steps. ’In-steps’ refers to the procedure of interrupting the PBM process and detaching the agglomerated powder adhering to the inner walls of the vessel. This task was repeated every hour and a half of the PBM process for a total of 12 h, and the results were compared with those of the 12 h continuous PBM process of the same mixture. In addition, the procedure was repeated with different amounts of mixture (100 g and 150 g) to determine the most efficient method of producing the material as a function of time. As for the thermoelectric profile of the powder, the data showed results in direct agreement with those in the literature.

Fabrication of Bismuth–Antimony–Telluride Alloy/Poly(3,4-ethylenedioxythiophene) Hybrid Films for Thermoelectric Applications at Room Temperature by a Simple Electrochemical Process

In this study, we synthesized flexible bismuth–antimony–telluride (Bi0.5Sb1.5Te3 (BST))/poly(3,4-ethylenedioxythiophene) (PEDOT) composite films using a simple two-step electrochemical deposition process. After electrochemically polymerizing ethylenedioxythiophene (EDOT) first on the gold-coated polyethylene terephthalate (PET), BST was deposited using the PEDOT layer as a working electrode. The effect of electrochemical potential on the morphology and crystal structure of the electrochemically deposited BST alloy was investigated through scanning electron microscopy and X-ray diffraction. The results show that a cauliflower-like morphology appears with a preferential orientation along the (110) direction of Bi0.5Sb1.5Te3 within the proper potential range. We also optimized the deposition time to achieve higher thermoelectric performance on the BST/PEDOT composite film. The optimal BST/PEDOT film produced by electrochemical deposition of BST for 80 min showed superior performance compared to other previously reported organic/inorganic composite materials. The maximum power factor was about 427 μW m–1 K–2 at an electrical conductivity of 167 S cm–1 and a Seebeck coefficient of 160 μV K–1. This process can be readily applied to practical fabrication of efficient thermoelectric materials.

Transformation during In Situ Heating of Bismuth Antimony Telluride Nanoplates

Transformation during In Situ Heating of Bismuth Antimony Telluride Nanoplates

Development of film strain converters based on bismuth-antimony tellurides

The article discusses the mechanism of fatigue failure of a material and a method for determining the process of material fatigue by developing semiconductor polycrystalline converters based on bismuth-antimony tellurides. The technological process of obtaining semiconductor film sensors by the method of thermal vacuum evaporation of a mixture of granular materials is described.

Development of methods for studying intergranular surface features in semiconductor heterogeneous polycrystals of bismuth-antimony tellurides with the imposition of electric and deformation fields

The article discusses the technique and tools for studying the role of the effective density of electronic surface states innanocrystalline semiconductor films when cyclic deformation is applied directly from the analysis of experimental data. The surface electron states play the role of recombination and trapping centers depending on the number of carriers, the electron capture section and hole, the concentration of surface states of their type and energy position. To determine the effective density of surface states, we found both a change in the Fermi level and a change in the density of the effective surface charge. The effective density of electronic surface states was determined from the measured variations in the active resistance and capacity of nanocrystalline films of bismuth-antimony tellurides upon the application of irreversible deformation, and its strain dependence was found. From data analysis, one can judge the irreversibility of heterogeneous structures during deformation, that is, the electronic structure of a nanocrystalline semiconductor film changes greatly when cyclic deformation is applied.

House electrical generation using thermoelectric cinder block: Case study on Lebanese hollow block

The work presented in this article describes thermoelectric effect in cinder blocks in order to generate electricity in houses through heat waste harvesting. The study consists of developing a numerical model formed by a heat transfer equation coupled to thermoelectric equations to study the performance of thermoelectric generators(TEG) incorporated inside Lebanese hollow blocks through two simulations using finite difference and finite element schemes. Results showed a voltage of 5.85 mV produced from a single 8.6 × 0.4 × 0.4 cm3 thermoelectric leg made of Bismuth Antimony Telluride for a temperature difference ΔT = 30 K. Then, a design of three TEGs with 123 thermoelectric legs incorporated inside a hollow block was tested and validated numerically using both methods, the main results obtained for ΔT = 30 K, showed a voltage ΔV = 0.72 V, a current I = 0.06 A and a figure of merit ZT = 0.55. The design was then optimized for economic purposes; an optimum model was chosen with a final cost of 8880 $. Different suggestions were also presented to enhance the thermoelectric performance of the model.

Compositional Fluctuations Mediated by Excess Tellurium in Bismuth Antimony Telluride Nanocomposites Yield High Thermoelectric Performance

Compositional Fluctuations Mediated by Excess Tellurium in Bismuth Antimony Telluride Nanocomposites Yield High Thermoelectric Performance

Shift of tellurium solid-solubility limit and enhanced thermoelectric performance of bismuth antimony telluride milled with yttria-stabilized zirconia balls and vessels

As a thermoelectric material, Bi0.3Sb1.7Te3.0+x (x = 0‒0.05) was fabricated by mechanical alloying using yttria-stabilized zirconia (YSZ) ceramic balls and vessels, followed by hot pressing. The effects of the added tellurium on the thermoelectric properties of Bi0.3Sb1.7Te3.0 fabricated with YSZ milling media were investigated. All sintered samples were isotropic and showed p-type conduction. The tellurium solid-solubility limit for Bi0.3Sb1.7Te3.0 was determined to be x = 0.01 by differential thermal analysis (DTA). The solid-solubility limit of the sample fabricated using YSZ was narrower than that of the congener prepared with Si3N4 balls and stainless-steel metal vessels. Among the evaluated compositions, the Bi0.3Sb1.7Te3.01 sintered disk had the highest dimensionless figure of merit, ZT = 1.30, at room temperature. This value was superior to that of Bi0.3Sb1.7Te3.0+x fabricated using metal vessels. Thus, selection of the milling media affected the optimum doping amount and maximum ZT.

Hidden role of intrinsic Sb-rich nano-precipitates for high-performance Bi2-xSbxTe3 thermoelectric alloys

Nanostructuring is a universal strategy to improve the figure of merit (zT) of thermoelectric (TE) materials by the substantial decrease of lattice thermal conductivity due to the intensive scattering of phonons at interfaces. However, nanostructured bismuth antimony telluride alloys with foreign nanosized phases usually suffer from the degradation of carrier mobility at incoherent interfaces. The results reported here describe an approach to generate intrinsic Sb-rich precipitates that have a synchronal effect on micro-grained Bi0.5Sb1.5Te3 alloy. The designed formation of nanosized Sb-rich precipitates by dissolving excess Pb into Bi0.5Sb1.5Te3 matrix intensifies the phonon scattering and modulates the carrier transport simultaneously. By employing density functional theory calculation, transmission electron microscope and atom probe tomography, the role of Pb substituting for Sb site on the evolution of Sb-rich nanophase is clarified and the compositions and crystal structures of the precipitated Sb-rich phases are analyzed, revealing various interface structures. The optimized Bi0.5Sb1.5Te3 + 0.22 wt.% Pb sample shows a maximum zT value of 1.32 at 400 K with an outstanding average zT value of 1.2 over 300 K to 500 K. This work identifies the hidden role of intrinsic Sb-rich precipitates in Bi0.5Sb1.5Te3 alloys and provides an effective way beyond nanostructuring to develop high-performance bismuth antimony telluride thermoelectric alloys.

High-Performance Bismuth Antimony Telluride Thermoelectric Membrane on Curved and Flexible Supports

High-Performance Bismuth Antimony Telluride Thermoelectric Membrane on Curved and Flexible Supports

Effect of Powder Heat Treatment on Chemical Composition and Thermoelectric Properties of Bismuth Antimony Telluride Alloys Fabricated by Combining Water Atomization and Spark Plasma Sintering.

In this work, Bi0.5Sb1.5Te3 materials were produced by an economically viable and time efficient water atomization process. The powder samples were heat treated at different temperatures (673 K, 723 K, 743 K, 773 K, 803 K, and 823 K) followed by spark plasma sintering (SPS). It was found that the Te evaporated slightly at 723 K and 743 K and became dominated at 773 K, 803 K, and 823 K, which severely influences the thermoelectric properties. The electrical conductivity was significantly improved for over 803 K heat treated samples due to the remarkable improvement in hole concentration. The power factor values for the 803 K and 823 K samples were significantly larger at T > 350 K compared to other samples. Consequently, the peak ZT of 0.92 at 350 K was obtained for the 803 K sample, which could be useful in commercial thermoelectric power generation.

Structural Design Optimization of Micro-Thermoelectric Generator for Wearable Biomedical Devices

Wearable sensors to monitor vital health are becoming increasingly popular both in our daily lives and in medical diagnostics. The human body being a huge source of thermal energy makes it interesting to harvest this energy to power such wearables. Thermoelectric devices are capable of converting the abundantly available body heat into useful electrical energy using the Seebeck effect. However, high thermal resistance between the skin and the device leads to low-temperature gradients (2–10 K), making it difficult to generate useful power by this device. This study focuses on the design optimization of the micro-thermoelectric generator for such low-temperature applications and investigates the role of structural geometries in enhancing the overall power output. Electroplated p-type bismuth antimony telluride (BiSbTe) and n-type copper telluride (CuTe) materials’ properties are used in this study. All the simulations and design optimizations were completed following microfabrication constraints along with realistic temperature gradient scenarios. A series of structural optimizations were performed including the thermoelectric pillar geometries, interconnect contact material layers and fill factor of the overall device. The optimized structural design of the micro-thermoelectric device footprint of 4.5 × 3.5 mm2, with 240 thermoelectric leg pairs, showcased a maximum power output of 0.796 mW and 3.18 mW when subjected to the low-temperature gradient of 5 K and 10 K, respectively. These output power values have high potential to pave the way of realizing future wearable devices.