Papers by Keyword: Bi₂Te₃

Abstract: In this study, SnO₂ nanoparticles of wt% 2, 4, 6, and 8 were uniformly composite in Bi₂Te₃ matrix. SnO₂ nanoparticle was synthesized using co-precipitation method. The result shows that based on XRD and EDS analysis the composites do not contain any impurities. The thermoelectric properties of the composites strongly depend on the Seebeck coefficient. The highest value of Seebeck coefficient of -177 µV/K is obtained at around 375 K for the 4% SnO₂/Bi₂Te₃ sample. This yields the highest value of the power factor of 4.0 × 10^-3 Wm^-1K^-1 compared to the pure Bi₂Te₃ synthesized using the same procedure by 14.3%. This result demonstrates that the thermoelectric properties of Bi₂Te₃ can be improved using oxide nanoparticles.

Abstract: Bi₂Te₃ nanowires are prepared by a low-cost and facile hydrothermal method without any surfactant. The structure and morphology of the nanowires are characterized by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscope. The influences of experimental conditions on the products are investigated. The growth mechanism is proposed based on the experimental results. This work is promising for the synthesis of Bi₂Te₃ nanowires with less impurity.

Abstract: Compared with block and quantum well thin-film materials, nanowire materials can have better thermoelectric properties and higher merit of ZT values. Electro-chemistry method was used to deposit nanowires in the highly ordered holes of AAO (Anodic Aluminum Oxide). Several conditions were discussed and experimented to determine an appropriate condition for the co-deposition of Bi and Te. Some optimization measures are proposed to obtain more stable fabrication results. Analysis demonstrates that the nanowire grew along the pores from the bottom to the top.

Abstract: Thermoelectric materials are a novel class of materials having unique characteristics. They are Seebeck and Peltier effect materials and are used as thermocouples, for thermoelectric cooling of microelectronic products, as thermoelectric converter for energy conservation etc. Due to their versatility of behaviour, they are now used as construction materials for microelectronic equipment, wireless sensors also. This paper aims at elaborating the development of such materials by compiling the recent and ongoing researches. In this regard, the research developments of some newer materials by other investigators have been presented here. Brief details of the development of thermoelectric generation, thermoelectric cooling, thermoelectric power generator for wearable systems, nano-thermocouple, thermoelectric Peltier microcoolers etc. are presented. In these elaborations, it is shown by the respective investigators that these TE materials can be effectively used in heavily doped semiconductor, thin films, quantum well etc.

Abstract: Bi₂Te₃ bulk materials were prepared by combining chemical bath method and hot pressing at 80 MPa and 375 °C for 1 h. The samples before and after hot pressing were examined by X-ray diffraction, and the fracture surface of the bulk materials was observed by field emission scanning electron microscopy (FESEM). The electrical transport properties of the bulk materials were measured from room temperature up to 250 °C under Ar. The results indicate that sulfur addition can prevent the oxidation of Bi₂Te₃ nanostructures; however, it is not good to the thermoelectric properties of Bi₂Te₃ under the present synthesis conditions.

Abstract: Temperature dependencies of the Seebeck coefficient, electrical conductivity, heat conductivity and the dimensionless thermoelectric figure of merit ZT of p-Bi₂Te₃, n-Bi₂Se₃ and Sb₂Te₃ doped by Fe or Cr have been investigated in the temperature interval 7 < T < 300 K. At T=4.2 K the Shubnikov-de Haas and Hall effects have been measured. By increasing the Fe content, the hole concentration decreases in p-Bi_2-xFe_xTe₃, while the electron concentration increases in n-Bi_2-xFe_xSe₃. The hole concentration decreases in Sb_2-xCr_xTe₃ with Cr doping. This demonstrates that Fe or Cr act as donors. The Seebeck coefficient increases in p-Bi_2-xFe_xTe₃ and Sb_2-xCr_xTe₃ with increasing Fe or Cr content, while it decreases in n-Bi_2-xFe_xSe₃.

Abstract: The thermoelectric materials based on p-type Bi2Se3xTe3 (1-x) bulk products and dispersed with x compositions of Se (x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were fabricated using standard solid-state microwave synthesis procedures. The products were characterized by X-ray diffraction (XRD). The XRD characterizations revealed that these products are pure Bi2Te3 and Bi2Se3 with uniform structures. The electrical properties of the Bi2Te3, Bi2Se3 and Bi2Se3xTe3 (1-x) samples were measured in the temperature range of 303–523 K. The highest value of the Seebeck coefficient was 176.3 μV/ K for the Bi2Se0.6Te2.4 sample, but only 149.5 and 87.4 μV/K for the Bi2Te3 and Bi2Se3 samples, respectively.

Abstract: Thermoelectric is an ever evolving field that serves many critical needs (cooling and power generation) in the industry. The key objective of this work is to fabricate Bismuth Telluride (Bi₂Te₃) thin-films by varying the various process parameters using a radio-frequency (RF) magnetron sputtering disposition technique. Characterization methods such as four point probe resistivity, surface profiler, atomic force microscopy (AFM), X-ray diffraction (XRD), Seebeck coefficient and thermal diffusivity are performed on the N and P-type Bi₂Te₃ films. The samples are analysed for their electrical properties in relation to the evolved microstructures, for how the process parameters of sputtering and annealing affect these changes. The results demonstrate that N-Type film (S2) processed using sputtering parameters of 7mT, 100W, 50sccm of argon flow under room temperature for 30mins with no annealing and the P-Type film processed using sputtering parameters of 7mT, 100W, 60sccm under room temperature for 30mins with institute annealing at 200°C for 2h exhibit desirable thermoelectric properties suitable for cooling application in microelectronic and optoelectronic devices, optimizing their performance and reliability.

Abstract: The paper deals with a coating CuO thin film coating on the surface of semiconductor thermoelements (Bi2Te3). In addition, the recycled external exhaust heat is used to generate electric power, further enhancing the thermoelectric conversion efficiency of the thermoelectric generator (TEG). By using electrophoresis deposition, a CuO nanofluid with high suspension stability and good dispersion is deposited on an aluminum foil at a thickness of 0.1mm. This film is conjugated with the top and base of a semiconductor thermoelements (Bi2Te3), and a thermoelectric generator is assembled in parallel with the modified thermoelectric material. Experimental results show that the CuO nanofilm coating on the surface of semiconductor thermoelements can enhance the overall heat conduction and thermoelectric conversion efficiency of thermoelectric generators by as much as 30%.

Abstract: The Bi2Te3 compound was synthesized by mechanical alloying (MA) of highly pure constituents of Bi and Te powders, and then was consolidated by spark plasma sintering (SPS) method. The MA-derived alloy formation was characterized by X-ray diffraction (XRD), and the microstructure change was investigated through scanning electron microscopy (SEM). The thermoelectric properties were measured using a Seebeck Coefficient/Electrical Resistance Measuring System. The influence of MA time on the thermoelectric properties of the SPS-sintered samples was investigated to find the optimal MA condition for the powder synthesis and thermoelectric properties. The obtained results showed that the sample with the MA time of 6 h exhibited the optimal electrical transport properties. The maximum power factor of over 2.0 × 10-3 W/m K2 was obtained between 323 K and 423 K.