Effects of Low Rotational Speed on Crystal Orientation of Bi<sub>2</sub>Te<sub>3</sub>-Based Thermoelectric Semiconductors Deformed by High-Pressure Torsion

A Bi2Te3-based thermoelectric semiconductor was subjected by high pressure torsion (HPT). Sample disks of p-type Bi0.5Sb1.5Te3.0 were cut from sintered compacts that were made by mechanically alloying (MA) followed by hot pressing. Disks were subjected by HPT with 1, 5 and 10 turns at 473 K under 6.0 GPa of pressure. Crystal orientation was investigated by X-ray diffraction. Microstructures were characterized using scanning electron microscopy. Results indicated that HPT disks after 5 turns had a preferred orientation and a fine grain compared with pre-HPT disks while the orientation factor was decreased after HPT using 10 turns. The power factor had a maximum value at 5 turns as determined by measuring its thermoelectric properties. A maximum power factor of 4.30×10-3 Wm-1K-2 was obtained for HPT disks after 5 turns. This value was larger than that for the pre-HPT disk. The over-HPT of 10 turns was found to have caused a decrease in the preferred orientation leading to a low power factor.

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Effect of single-crystal orientation on the molybdenum structure and hardness upon high pressure torsion

International Journal of Refractory Metals and Hard Materials ◽

10.1016/j.ijrmhm.2021.105754 ◽

2021 ◽

pp. 105754

Author(s):

L.M. Voronova ◽

T.I. Chashchukhina ◽

T.M. Gapontseva ◽

A.M. Patselov ◽

V.P. Pilyugin ◽

...

Keyword(s):

High Pressure ◽

Single Crystal ◽

Crystal Orientation ◽

High Pressure Torsion

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Control of Crystallographic Orientation and Grain Refinement in Bi2Te3-Based Thermoelectric Semiconductors by Applying High Pressure Torsion

Materials Science Forum ◽

10.4028/www.scientific.net/msf.584-586.1006 ◽

2008 ◽

Vol 584-586 ◽

pp. 1006-1011 ◽

Cited By ~ 10

Author(s):

Maki Ashida ◽

Takashi Hamachiyo ◽

Kazuhiro Hasezaki ◽

Hirotaka Matsunoshita ◽

Masaaki Kai ◽

...

Keyword(s):

High Pressure ◽

Crystal Orientation ◽

High Pressure Torsion ◽

Crystallographic Structure ◽

Nominal Composition ◽

X Ray Diffraction ◽

X Ray ◽

Refined Microstructure ◽

Vertical Bridgman ◽

P Type

Prepared were p-type Bi2Te3-based thermoelectric semiconductors, having a grain-refined microstructure and a preferred orientation of anisotropic crystallographic structure. Disks with a nominal composition Bi0.5Sb1.5Te3.0 were cut from an ingot grown by the vertical Bridgman method (VBM) and deformed at 473 K under a pressure of 6.0 GPa by high pressure torsion (HPT). The crystal orientation was characterized with X-ray diffraction. The microstructures were characterized by using optical microscopy and scanning electron microscopy. It was found that the HPT disks had a fine and preferentially oriented grain compared to that of the VBM disks. Further, the power factor of the HPT disks was about twice as large as that of the VBM disks. These results indicate that HPT is effective for improving the thermoelectric properties of Bi2Te3-based thermoelectric semiconductors.

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