Recrystallization stimulated hierarchical structures for the simultane…
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논문명 | Recrystallization stimulated hierarchical structures for the simultaneous enhancement of Seebeck coefficient and electrical conductivity in Bi-Sb-Te alloys |
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저자 | Myeong-Won Lee, Peyala Dharmaiah, Chul-Hee Lee, Sung Ho Song, Jong-Hyeon Lee, Soon-Jik Hong |
저널명 | Journal of Alloys and Compounds |
게재년월 | 2020/5/28 |
Vol. pp |
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 Bi0.5Sb1.5Te3 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 Sb2O3 nanoparticles. The significant
improvement in power factor and relatively low kL 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 ¼ 0.75 at 350 K). The average ZT for
all the heat treated samples reached over unity in the range of 300e500 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.