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

Enhanced thermoelectric performance of Bi0.5Sb1.5Te3 composites through potential barrier scattering at heterogeneous interfaces

The inclusion of secondary phase in a matrix has been proven effective in diverse regimes of thermoelectric (TE) material research intended to attain high thermoelectric performance. Herein, we show that the introduction of semiconducting Zn4Sb3 alloys into a Bi0.5Sb1.5Te3 matrix to form ZnTe nanophase in situ causes enhanced electrical conductivity and reduced thermal conductivity. This is due to increase in the carrier concentration and intensified phonon scattering at interface potentials. These simultaneously increased the power factor by 17 % and achieved a remarkable reduction (25 %) of lattice thermal conductivity at 350 K for BST/2 wt% Zn(4)Sb(3 )composites. As a result, the largest value of ZT (1.35) was obtained at 350 K, which is 26 % higher than that of the Bi0.5Sb1.5Te3 matrix at the same temperature. Moreover, the maximum conversion efficiency was about 8.74 % at Delta T = 200 K for BST/2 wt% Zn4Sb3 composites, which is 25 % higher than that of a bare BST sample.11Nsciescopu

Influence of Spark Plasma Sintering Temperature on Microstructure and Tthermoelectric Properties of Cu-Doped Bi0.5Sb1.495Te3 Compound

Due to air pollution, global warming and energy shortage demands new clean energy conversion technologies. The conversion of industrial waste heat into useful electricity using thermoelectric (TE) technology is a promising method in recent decades. Still, its applications are limited by the low efficiency of TE materials in the operating range between 400-600 K. In this work, we have fabricated Cu0.005 Bi0.5Sb1.495Te3 powder using a single step gas atomization process followed by spark plasma sintering at different temperatures (623, 673, 723, and 773 K), and their thermoelectric properties were investigated. The variation of sintering temperature showed a significant impact on the grain size. The Seebeck coefficient values at room temperature increased significantly from 127 μVK to 151 μV/K with increasing sintering temperature from 623 K to 723 K due to decreased carrier concentration. The maximum ZT values for the four samples were similar in the range between 1.15 to 1.18 at 450 K, which suggest these materials could be used for power generation in the mid-temperature range (400-600 K)

Synergistic Optimization of the Thermoelectric and Mechanical Properties of Large-Size Homogeneous Bi0.5Sb1.5Te3Bulk Samples via Carrier Engineering for Efficient Energy Harvesting

Manufacturing an economically viable, efficient commercial thermoelectric (TE) module is essential for power generation and refrigeration. However, mediocre TE properties, lack of good mechanical stability of the material, and significant difficulties involved in the manufacturing of large-scale powder as well as bulk samples hinder the potential applications of the modules. Herein, an economically feasible single-step water atomization (WA) is employed to synthesize BST powder (2 kg) by Cu doping within a short time and consolidated into large-scale bulk samples (500 g) for the first time with a diameter of 50 mm and a thickness of about 40 mm using spark plasma sintering (SPS). The incorporation of Cu into BST greatly boosts the carrier concentration, leading to a significant increase in electrical conductivity, and inhibits the bipolar thermal conductivity by 73%. Synchronously, the lattice contribution (κL) is greatly reduced by the effective scattering of phonons by comprising fine-grain boundaries and point defects. Therefore, the peak ZT is shifted to the mid-temperature range and obtained a maximum of ∼1.31 at 425 K and a ZTave of 1.24 from 300 to 500 K for the BSTCu0.05 sample, which are considerably greater than those of the bare BST sample. Moreover, the maximum compressive mechanical strength of large-size samples manufactured by the WA-SPS process is measured as 102 MPa, which is significantly higher than commercial zone melting samples. The thermoelectric module assembled with WA-SPS-synthesized BSTCu0.05 and commercial n-type BTS material manifests an outstanding cooling performance (-19.4 °C), and a maximum output power of 6.91 W is generated at ΔT ∼200 K. These results prove that the BSTCux samples are eminently suitable for the fabrication of industrial thermoelectric modules. © 2022 American Chemical Society.FALS

Correlation with the composition of the different parts of p-type Bi0.5Sb1.5Te3 sintered bulks and their thermoelectric characteristics

Evaporation of tellurium (Te) occurs during most of the fabrication methods which leads to a strong deviation on thermoelectric properties. Due to the existence of volatile tellurium has been a great challenge to determine the accurate chemical compositions in the Bi0.5Sb1.5Te3 compound for optimizing the carrier concentration. Herein, we systematically verify the reliability and understand the correlations between chemical composition and thermoelectric properties at different portions of large (25 mm), thick (30 mm) samples. The results reveal that spark plasma sintered samples didn't show any significant evaporation of Te. However, the chemical composition slightly changed, resulting in the final thermoelectric figure of merit at different portions of thick samples varied typically within a 10% error. Moreover, this work supports that the selection of the powder fabrication and compaction method plays a crucial role on the final thermoelectric properties of the material, as the combining of gas atomization and spark plasma sintering can prohibit the evaporation of tellurium and any possible inhomogeneous stress field or temperature distribution in large-sized graphite die to SPS. (C) 2020 Elsevier B.V. All rights reserved.11Nsciescopu