1. Recrystallization stimulated hierarchical structures for the simultaneous enhancement of Seebeck coefficient and electrical conductivity in Bi-Sb-Te alloys.
- Author
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Lee, Myeong-Won, Dharmaiah, Peyala, Lee, Chul-Hee, Song, Sung Ho, Lee, Jong-Hyeon, and Hong, Soon-Jik
- Subjects
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THERMAL conductivity , *SEEBECK coefficient , *ELECTRIC conductivity , *HEAT treatment , *PHONON scattering , *THERMOELECTRIC materials - Abstract
Decoupling the Seebeck coefficient, electrical and thermal conductivity has been a great challenge in efforts to obtain thermoelectric materials with a high figure of merit (ZT) for power generation and cooling applications. In this work, p-type Bi 0.5 Sb 1.5 Te 3 samples were fabricated by combining gas atomization and spark plasma sintering. Heat-treatment and subsequent consolidation during SPS stimulated the recrystallization of grains and reduced texture, contributing to reduced carrier scattering. This enhanced carrier mobility by 29%. The recrystallization also induces a hierarchy of fine and coarse crystal grains with random orientations. This mixed microstructure contributed to the simultaneous enhancement of the Seebeck coefficient and electrical conductivity, while reducing lattice thermal conductivity, due to effective phonon scattering by the fine grains and Sb 2 O 3 nanoparticles. The significant improvement in power factor and relatively low κ L resulted in a peak ZT of 1.1 at 350 K for the 470 °C treated sample. This was about 47% higher than the initial sample (ZT = 0.75 at 350 K). The average ZT for all the heat treated samples reached over unity in the range of 300–500 K. This work suggests that the spark plasma heat treatment and consolidation processes enable the recrystallization, allowing the thermoelectric properties to be decoupled, enhancing ZT. Image 1 • The hierarchical structures were formed in Bi 0.5 Sb 1.5 Te 3 alloys via recrystallization. • Decoupled the electrical and thermal properties by forming the hierarchical structures. • Heat-treatment and subsequent consolidation during SPS stimulated the recrystallization of grains and reduced texture. • ZT enhanced by 47% for recrystallized samples than the initial samples. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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