Thermoelectric Performance of Nanostructured Bismuth-Tellurium and Bismuth-Antimony-Tellurium Powders Fabricated by Galvanic Displacement Reaction Process

Thermoelectric devices are of promising interest for applications as heat pumps and power generators. The efficiency of thermoelectric devices can be intended by figure of merit (ZT=(S²σT/κ), where S, σ, κ, T are the seebeck coefficient, electrical conductivity, thermal conductivity, and absolute temperature, respectively [2]. In this study, by utilizing the nanosize powder, it is intended to enhance the figure of merit to obtain a low thermal conductivity.

 The powder of bismuth-tellurium and bismuth-antimony-tellurium was fabricated using alumina substrate in acid aqueous solution by galvanic displacement reaction process [3]. The advantage of this process is that it can be relatively simple and easy to produce powders from few micrometer to hundreds nanometer in size, and the mass production is facile.

 The morphologies of bismuth-tellurium and bismuth-antimony-tellurium powders were characterized using field emission scanning electron microscope (FESEM, JEOL JSM 7000F). X-ray diffraction (XRD) patterns have been investigated with a Bruker Coporation (Cu kα). The composition ratio of powders was confirmed using ICP (PerkinElmer, Optima-4300 DV).

 These nanocrystalline bulk materials were prepared by hot pressing nanopowders at 350 °C for 30min with a uni-axial pressure of approximately 40 MPa to form pellets. The measurements of electrical resistivity and seebeck coefficient of the pellet samples have been carried out by using a equipment ULVAC ZEM-3 for operating temperature range of 30 to163 °C. The thermal conductivities have been measured by using a laser flash (ULVAC-RICO).

Fig 1. SEM images of a) Bi₂Te₃, and b)Bi_0.5Sb_1.5Te₃powders fabricated by galvanic displacement reaction process.

Reference

[1] B. Poudel, Q Hao, Y Lan, and Z. Ren, Science, 320, 634, (2008)

[2] Z. Lu, L.P. Tan, X. Zhao, and H.H. Hng, J. Mater. chem. C, 1, 6271, (2013)

[3] K. Zhuo, M.G. Jeong, and C-H. Chung, RSC Advances, 3, 12611, (2013)